We call this the Pine Board Project for a reason and that’s because we will actually be building a transmitter on a pine board, so you can see the circuitry. We want to try to not only build things, but we want to teach you what you’re doing when you are building it. You won’t just learn to solder. In this first project, you will build a simple field strength meter, but that’s just the beginning. You will also build a 300-volt power supply, a microphone preamplifier, a transmitter, and a final tuner. Once all of that is done we will put it all together. The goal is to try to help you learn a little bit more about the schematics and how to build all while having fun.
*Special thanks to W4IQN for the graphics!
Caution: This is a fun project for all ages, but kids should be doing this with adult supervision due to the danger of high voltage. Anyone using these instructions must read the Heil Sound disclaimer before proceeding.
Click here to read it!
Project 1: Field Strength Meter
From HAMNation episode 289.
Parts and tools:
A pine board about 6 x 6 in.
Soldering iron
Rosin core solder
Small screws
Terminal strips (4s or 5s are best)
1n914 Diode
50k Potentiometer (a pot)
Meter 100 micro Amp
.01 Capacitor
RF Choke 2.5mH
Antenna 19 inch piece of solid wire (a coat hanger works fine)
Having trouble finding the parts? Check out these sites.
https://www.tubesandmore.com/
http://gateway-electronics.com/
http://vacuumtubes.com/ (best tube supplier)
Mount terminal strips on the pine board close, but not touching.
Every diode is polarized and as you reference the pictorial or the schematic you will see that band on the diode has to be placed in a very specific position with the band toward the plus side before soldering
Solder the choke into the terminal strips.
Solder the potentiometer from the choke/bottom terminal strip to the upper right side of the terminal strip.
Now it’s time to solder on the Meter. Solder the green wire to the upper right side of the terminal strip attached to the potentiometer and the red wire to the upper left side of the terminal strip attached to the diode. (picture)
Don’t forget to put your knob on your pot and attach an antenna. (picture)
The finished Field Strength Meter should look like this and now you’re ready to test it!
If you’re new to Ham Radio you might be thinking, “What the heck is Bob talking about (aka vocabulary terms)???” We’ve got you covered!
Potentiometer – (or a pot) is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider.
Capacitor – a device for accumulating and holding a charge of electricity, consisting of two equally charged conducting surfaces having opposite signs and separated by a dielectric.
Diode – a device, as a two-element electron tube or a semiconductor, through which current can pass freely in only one direction.
Project 2: Power Supply
From HAMNation episodes 290, 291, 292, 293, 294, and 295
Parts and Tools:
261G6 transformer
3- electrolytic capacitor 20 mfd@ 450 v
2- 1k ohm 2 watt resistor
Fuse holder
Fuse
Power switch
6X5 vacuum tube
Ceramic octal socket
2- solder-type terminal strips – 6 lug
3 lug barrier terminal strip
Pilot light socket
Pilot bulb (6.3v)
AC power cord w/plug
We started the Pine Board Project with a 6X5 vacuum tube rectifier to change the secondary AC voltage of the transformer to D.C. That tube is a half-wave rectifier. See below for a great video explanation from George Thomas about how and why this works. It produces about +150 volts of D.C. In part of the learning curve we create with the Pine Board Project, I introduce a full wave rectifier which is actually four diodes in one package that will
produce +350 volts in this circuit. There are two ways to do this. The first is to mount and solder the bridge into an 8 pin male plug, disconnect the center tap from the ground – very important as the transformer center tap is no longer connected. Solder it to an unused terminal strip so it will not come in contact with anything. Plug that into the 8 pin socket that the 6X5 was plugged into. This +350 volts will now allow the 6AG7 to produce around 5 watts of RF output. The second way is to remove the tube socket, mount a 6 or 7 lug terminal strip where the bridge rectifier can be permanently mounted here the tube socket once resided.
Wiring before transformer and tube socket.
Project 3: Microphone Pre-Amp
We haven’t actually started this portion of the project on HAMNation yet, but for those that like to work ahead here is the parts list and the schematic.
Parts and Tools:
1 – 12AX7 tube
1 – tube socket (9 pin miniature)
2 – tube socket stand-off ½”
3 – solder-type (6 lug) terminal strip *
1 – barrier-type (4 lug) terminal strip
1 – electrolytic capacitor 10mfd/ @ 450v
1 – electrolytic capacitor 10mfd @ 25v
1 – ceramic disc capacitor 0.0047 mfd
2 – ceramic disc capacitor 0.001 mfd
1 – ceramic disc capacitor 0.001 mfd **
1 – ceramic disc capacitor 0.01 mfd
1 – ceramic disc capacitor 0.01 mfd **
1 – ceramic disc capacitor 0.047 mfd
2 – ceramic disc capacitor 0.1 mfd **
1 – resistor 1k Ω
2 – resistor 100k Ω
1 – resistor 100k Ω **
1 – resistor 1M Ω
1 – variable resistor 50k Ω
1 – variable resistor 50k Ω **
1 – variable resistor 10k Ω **
1 – knob for above
2 – knobs for above **
2 – ¼” phone jack
2 – ¼” phone plug
1 – switch, SPDT **
* trim length as necessary
** parts needed for the optional EQ circuit
Project 4: Transmitter
Parts List:
1 – 6V6 tube
1 – 6AG7 tube
2 – tube socket (8 pin octal) (B) P-ST8 250MT
4 – stand-off, ¾” – 1″ long for above (F) #58031
4 – solder-type (6 lug) terminal strip * (B) P-0702H
1 – barrier-type (4 lug) terminal strip (C) BB375-4
1 – electrolytic capacitor 10mfd/ @ 450v (B) C-ET10-450
1 – electrolytic capacitor 47mfd @ 50v (B) C-ET47-50
1 – silver mica capacitor 500 pf
1 – silver mica capacitor 100 pf
1 – ceramic disc capacitor 0.001 mfd (B) C-D- 2000 .001
1 – polypropylene capacitor 0.0047 mfd (B) C-LD0047-630
1 – variable capacitor 365 pf, single gang (B) C-V365
1 – knob for above
1 – resistor 100 Ω
2 – resistor 22 kΩ, 1 watt
1 – resistor 56 KΩ
1 – resistor 100 KΩ
1 – RF choke 2.5 Mh
1 – DC filter choke 4 H, 50 ma (B) P-CF 22707
1 – coil: MFJ #404-0811-1
1 – crystal FT-243 type 3.885 MHz ** (E) 3885mHz
1 – socket for crystal (above)
1 – antenna jack (SO-239) (D) MFJ-7721
1 – alligator clip
* trim length as necessary
** For 40 meter operation, add a crystal 7.290 MHz
*** a kit of parts is available
Parts Suppliers:
(A) SND Tube Sales, www.vacuumtubes.com
(B) Antique Electronics, www.tubesandmore.com ***
(C) Radio Daze, www.radiodaze.com
(D) MFJ, www.mfjenterprises.com
(E) Amateur Radio AF4K, www.af4k.com
(F) Ace Hardware
Pine Board: Hobby Lobby “wood pile”
Shown above: 6AG7 Bottom
Shown above: 6V6
Bob, heard you on QSO Today talking about how we need more Elmers. Thanks for stepping up with this project and Elmering a whole lot of hams. My question is:
Could their be a side circuit to the power supply that would incorporate the equivalent of the Chip Stick so that whenever you switched it to the Off position the Chip Stick Circuit would be connected? Maybe incorporate a red LED into the circuit to warn that power was still draining from the capacitors.
Looking forward to the next step in the project on tonight’s show!
Hi Steve
Thanks for your interest and comment. Yes, that could be done but as noted in each program so far when both tubes are up and running the pair of 1K resistors, plus the load from the pre amp and transmitter, bleed the high voltage to zero in about 2 seconds.
The Chip Stick is just during the build… keep on building, Steve!
BOB
right but you a using the standard hack clip on the coil?. easy but theres no field on the outside of the coil. its all inside. I suggest a brass slide rod instead inside the coil. Different yes?
j
Bob,
Congrats on an excellent project series. It is so important today to get young folks (and those young at heart) interested in both the art and science of electronics. This is an excellent way of doing so and you and your team are to be commended.
Best 73 — Nick K5EF
Thanks, Nick!
I am excited to begin this project. When I was a young teen I decided that I wanted to build both a transmitter and receiver (so long ago it was that we had to chisel our own tubes out of rocks). This project will help to fulfill that goal. I’m having a hard time waiting for the next installment. Thank you very much for presenting this project. I am hoping that you will follow it on with a receiver, though.
Would it be possible to post links so the schematics and pictorals could be down loaded as pdfs?
Again, thank you very much.
73,
Chas AD0UY
Hi Bob,
I have a HM-12 I hope to use with this project. Do I need a transformer to couple it to the input of the preamp?
Thank you for taking the time to do this project. I really enjoyed building the power supply.
73,
Tim
Hi Tim!
I am working pin what will be the best microphone for the PNP. I believe the HM 12 will be good but stay tuned as we get the pre amp built and running during the next few weeks.
Thank you!
Bob
Could you please post the schematics larger and at higher resolution? Copying the picture and enlarging it does not work.
Ron – should be able to enlarge the images. Thanks
BOB
I finished building the preamp today, connected the power supply, switched it on, but didn’t see any smoke. Yeah!
I have a few questions regarding microphones and testing. I have a couple really old microphones (dynamic I believe) that work when I plug them into my laptop. Very weak audio when I make a recording on the laptop, but they seem to work. Is this preamp designed to work with dynamic microphones?
I do not know how to test the preamp. Can I use a voltmeter across designated test points to verify operation? I also have an audio signal generator and an oscilloscope, but could use some advice regarding safe input level and expected output levels.
Great fun. Thank you for sharing your knowledge with us.
Jim K9JWP
Jim
I test the preamp by connecting it into my powered JBL monitors. Any type of powered speaker or PA amp and speakers. You can certainly feed an audio generator into the input and look at the output on a scope. Should get you at least 1/2 volt or more. Lots of plans for this project so stay tuned and stay in touch. Alwasy open for ideas and thoughts, Jim
BOB
Bob
Glad you are getting this on line where I can get the parts list and schematics. It is hard to work from the screen shots Ii have taken during Ham Nation.
I appreciate you mentioning me on a couple of show. It really helps keep the enthusiasm up.
Maybe I will see you on the air soon
Bill KN4CJS
Interesting side note the last three letters of my call Just happen to to be what I have spent the last thirty five years doing, I have work as a Criminal Defense Attorney in the Criminal Justice System. Funny how thing work out.
KN4CJS
I decided to put my pines on 7275. In the window but away from wrong gamers.
Still loving it.
Donve3lyx
I notice a possible typographical error in the preamp BOM. There is an electrolytic capacitor listed as 10 mfd @ 50v. The schematic shows an electrolytic 10 mfd @ 450v. The pictoral view also shows 450v capacitor.
Jim
I test the preamp by connecting it into my powered JBL monitors. Any type of powered speaker or PA amp and speakers. You can certainly feed an audio generator into the input and look at the output on a scope. Should get you at least 1/2 volt or more. Lots of plans for this project so stay tuned and stay in touch. Alwasy open for ideas and thoughts, Jim
BOB
Sorry for that. Will get it corrected but actually a 450Volt cap will be just fine….Appreciate your comments and thoughts, Charles
Since it’s B+ -||- Ground, makes sense it would be 450V I think. It looks like the BOM has been updated.
Anyone know a source for the barrier strips and the switch for the PS?
Bill, N4DH
Terminal Blocks are available:
a) try your local Radio Shack – seem to be selling out their stock but the local stores might have some left
b) grainger.com has them
c) digikey has them – this is where I got mine
d) mouser – search for “Barrier terminal and blocks”
e) parts express – search for “power connectors”
switch – you can get one at Lowes hardware – search for “SPST switch”
Gene, W4IQN
Home Depot has a barrier strip available.
See http://m.homedepot.com/p/Armacost-Lighting-Quick-Connect-Terminal-Block-3-Pack-RFTERMBK/203569123
K5FNI Austin TX
Great project and superb documentation!
Well done, OM! de WA2EHV
Thanks Bob for a great project.
The Alamogordo Amateur Radio Club took this on as a group project and it has been so much fun to watch everyone learn to solder and trouble shoot the circuits. The Power supply works just great and about 60% finished with the preamp and can’t wait to see the RF section. You have taken many new hams into the world of building a useful device.
Thanks again
Terry W5TWY
Hi Terry
How is your Pine Board Project going with the club? Like to hear more and actually love to have you join us on one of the HamNation shows explaining how you are doing. Please stay in touch
BOB HEIL, K9EID
Hi Bob
The project is coming along great and we have made the last mod to the preamp circuit last week. We will do the finally testing this week and will let you know how well it works. Adding the bright switch was a great thing and the club members have really learned how the circuit works. Will send some pictures of the completed power supply and preamp when it is finely tested as it is mounted on one board. We have ordered a few items for the RF section like coil stock and tubes and are waiting for the schematic and parts list for it. We are having a really great time with this.
Thanks again
Terry W5TWY
for K5LRW (Alamogordo Amateur Radio Club)
Bob,
Excellent job building these homebrew components… I’m collecting my parts right now to follow along. Keep the projects coming…
Paul KF7NGK
Hi Bob,
What is the B+ you are aiming for out of your power supply? I am adapting some old junk parts and knowing what B+ you are aiming for would help in selecting filter resistor and capacitor values. Also, what kind of current draw do you anticipate from the various projects you have planned? Thanks
Mark K7MD
Mine shows190 VDC with no load.
Bill, N4DH
I love love love the concept and execution of these projects, your delivery and your “giving back” attitude, but, I am a professional photographer and it hurts to watch things out of focus. Thank you for your time, energy, and smarts in creating these videos. I can’t wait to start the first one. This is half the fun of ham radio! Maybe get a helper to man the camera while you work. Again, love them and thank you.
Hi Tom
Thanks for your note. Hey – I hate the focus situation, too but you probably know about some of these ”auto focus’ things…. it really is the only way we can do it since we are using little Logitek cameras. Them and SKYPE play games with us – and we don’t know it until we see the replay. All in all, the project has been good for so many and I look forward to helping you with your building. Always here to help
BOB HEIL
I’m ready for the transmitter??
Wayne….next week! See you then.
BOB
Hi Bob, been thinking to do the pine board project and my xyl asked me what is this going to cost to build.
Park part costs close enough…./Please!
The entire parts kit will be available from Antique Electronics supply. Should be about $150.00 https://www.tubesandmore.com/
How about info on the receiver please…….
Stephen,
I have been researching some of the receiver designs. Hope to come up with something for us all – lots to go before then, however. Glad you are here and enjoying the project.
BOB
Hello Dr Bob
Everything about the Pine Board QRP AM Project is awesome and a big “yes, yes” to your 2 band EQ mod. This build series opens the door for so many other possibilities, almost to many to mention on this thread. Like some, I am faithfully following along with the pace that you have established, but have taken the scrapheap approach. I am set on using surplus parts that I have collected over the years. My goal is to have a working QRP unit for “zero dollars”. I am defending the value of my surplus electronic junk and the space it takes up. 🙂
I decided to use engineered hardwood pieces that were remaining from a home project. I now can snap the pieces together for one big board or use the sections for future ideas. I have posted a few pictures on the bottom of my QRZ page. AMers are far and few in this area so I will probably will never talk to anyone on it, but I will enjoy listen to myself while adjusting the 2 band EQ.
Thanks for sharing your time and talent.. your friend in Virginia
Thanks for your nice note. Yes, this project can be built from the junk box or you can order all the new parts from Antique Electronics Supply. Hope you got to enjoy last night (June 28th) show. A great demonstration of the two band EQ with the ‘Bright’ control. Truly amazing. We will have that clip here on the web site next week along with the new schematic and parts layout.
Thanks for being with us and please stay in touch.
I finished the modulator yesterday and WOW !! I achieved the same results you created on the show.
I just need to get creative in the mounting of the brightness switch and mic jacks. I also 100% support your high voltage safety reminders that you emphasize on each show. It is a good build practice to never become relaxed around high voltage. I added a safety shield to my high voltage terminal strip. It is an inexpensive safety net for pointing fingers when builders are explaining or showing off their work. I used plastic from an old binder divider but a builder could cut a piece from the side of a milk jug. It doesn’t add to the cost of the project. I added pictures to my QRZ site on the bottom left.
Thanks again Dr. Bob for your time and efforts.. your friend in Virginia
Hi Bob,
I have finally started to get the parts together to build my own “Pine Board” project. Thanks for giving us something to learn about vacuum tubes and their application. Having grown up in the transistor era tubes always seemed a little like magic.
I have a very simple question though, for the power supply fuse, I think a 3 Amp would be sufficient but slow or fast? If there is a better choice, please let me know.
N6DGM – Dennis
Dr. Bob,
The equalization sections of your pre-amp schematics don’t match with capacitor quantity or values; which is correct?
I’m having a blast building along with you! Thanks so much for this project!
73, ke0efx
I wanted to take a moment to publicly thank you for all the hard work you are doing to create this platform for learning and for recreating the excitement that comes from building a piece of electronic gear and watching it ‘come to life’. One reason our hobby is special is that it involves the sharing of one’s knowledge with others in a way that they can have fun and be creative. So, for all you are doing for us, THANK YOU! It has been my distinct honor to be associated with the PBP.
Gene Workman, W4IQN
Always wanted to build a tube transmitter. Thank you for taking the time and work to make this possible Bob and all others involved with helping .
I am trying to work my way through the pre-amp and am having trouble understanding the schematic. The schematic shows two tubes and the parts layout shows one tube. So the tube is a double purpose tube. Can you explain how that happens and how to interrupt the schematic? Also the new and improved pre-amp has EQ and the published diagrams are still zero EQ adjustable so I am having troubles with the parts count and what exactly I need to complete the project. In one of the videos about the pre-amp a R6 is shown and it is for 33K one watt on a white board. Where do I insert that resistor? Is it from the power supply? Boy my hat size will increase from the extra knowledge.
Hi AJ
There is only one 12AX7 tube in the pre amp. The equalization takes place in between the two sections of the dual triode 12AX7. I do not understand your statement of ‘still zero EQ adjustable.’ There is a treble control and a bass control. We are publishing the schematics in the next two days if you missed them during one of the shows. If you want to email me at bob@heilsound.com I can email them to you.
BOB
Is there a complete parts list?
There are parts lists in each section, but not one for the entire project.
Steve
If you want to email at bob@heilsound.com I can send you each of the lists.
BOB
A big Aloha, Bob! Always anxiously await episodes of the show! Enjoy them so much. I especially have appreciated your desire to connect the amateur community with seemingly a fading art – that of building equipment and in “stages”. Love it, Bob and mahalo. Being way out here (and in an apartment) I’d want to get the pine transmitter set for qrp cw as I know of NO a.m. operation on the islands!! At any rate so reminiscent of my first transmitter on an orange crate with an 807. Luckily I didn’t get electrocuted in my grandma’s basement as a new VE4. Best Wishes, Dale (WH6EDT)
Hi Bob de W8edw (Ed)
Question: Are the pots Audio or Linear Taper?
I’m not seeing the updates that you sowed July 26 show.
Bill, N4DH
Hi Bill
We just put up many of the recent diagrams and photos. Have two schematics that will go up tomorrow.
Please check out the page.
Thank you
BOB
Bob, Just a quick question about the tube base in the power supply. How are the pins numbered? I note that there are two connection pins with no corresponding pin on the tube. I assume that the blanks are 4 and 6, making the rest numbers 1, 2, 3, blank, 5, blank, 7, and 8. Pin 1 is not wired, 2 and 3 are wired, 4 is blank, 5 is wired ,6 is blank, 7 is wired and 8 is wired.
Is this close to being correct? It is the only way I can figure where number 2 is to start wiring the socket as it is not numbered.
I received my parts from Antique Electronic and am ready to get started.
Enjoy the show each week. It is the highlight of my week .
Bill Brower KN4CJS
Bill,
I also bought my supplies from Antique Electronics. Look at the bottom (underneath) or the tube holder and you will see a very small number 1 on by one of the pins. I used that as my pin one reference. It is white and slightly raised. I put a mark on mine and then on the top side so I could see it from the top-side. My biggest problem to overcome was to find a way to raise the tube holder off of the board. I used a small piece of copper tubing from the plumbing department. The people cutting the tubing ended up giving it to me for no charge. I felt like a got a good deal and then I picked up several other parts – screws, wire and clips. Good luck.
Thanks AJ
I will look for the small number 1. I also got my parts from Antique Electronics. I just must have missed it.
Bill KN4CJS
Another easy source for standoffs is polyethylene tubing. It comes on a roll and is sold by the foot. I bought 1 foot for 39 cents, which is enough for 16 3/4″ tall standoffs. Just cut it to whatever length is desired.
Hi Bill
Thanks for your note and being with us.
The 6X5 pin out
3 and 5 are the HV of the transformer
2 and 7 are the filaments
Pin 8 is the D.C. output
Everything else is blank Hope this helps
BOB
If you have trouble finding risers/spacers, you can go to Lowes for a ‘faucet riser’, item #72227-30-38-2. Also called a ‘faucet connector’. It is a 3/8′ grey hard plastic tube – 30″ long and sells for $3.50 in the plumbing department. You can cut a ton of spacers from one tube with a handy knife, Xacto, single edge razor blade, or PVC cutter. Ace Hardware also has these.
Gene
Thank you for this Gene. Will pass it on!
Bob,
It’s been quite some time since I was excited about building something. Thanks for rekindling the builder’s spirit within. My buddy (VE3OJN) and I are going to be searching his junk box (he has an extensive junk box compared to me) for whatever we can find/use and we will purchase the rest. Can’t wait for the cold weather so we can have time to build. Woohoo!
Thanks again Bob and all who have contributed.
73
Steve – VE3EZB
Moose Creek, Ontario
Thanks for joining the Pine Board Project, Steve. No worry about the parts. There are several and actually many parts houses that carry the parts. Please pay attention to the parts list as we list the vendors for the parts. Antique Electronic Supply carries most. Please stay in touch…… good luck to you.
BOB HEIL, K9EID
What will the imput impudence be for the mic input, hi Z or 600 ohm?
What would be the minimum gauge wire for the project? Ordered my “kits” for
the preamp and transmitter from AES. Matt was very helpful, as I ordered some
additional parts.
Bill, N4DH
Hi Bill
The Pre amp is designed for a low impedance microphone input. Should you want to use a high impedance microphone, just add our XT-1 transformer. It works well. https://heilhamradio.com/products/xt1-high-impedance-transformer/
I like to use 22 ga. stranded hook up wire.
Please stay in touch
BOB
I cannot locate this choke 1 – RF choke 2.5 Mh (C) HC1534C on the Radio Daze web sight, I found these at Antique Electrictronic Supply https://www.tubesandmore.com/products/rf-choke-hammond, will both work, or is there a preference?
I am enjoying this series of projects, but I would like to start with the Field Strength Meter, and work my way up. Thanks again for all the time and effort you, and everyone else is putting into this, it is a great learning experience.
Not to worry. This is a common part and when they are sold out, I would guess they will be getting more in time. Hammond Mfg. in Canada is a supplier to distributors. You can get them today at On Line Components (Phoenix) $1.59, eBay 4/$20, and RF Parts $6. RF Parts is good but they do have a $20 minimum order. If you are going through the entire project, you will need two of these – one for the meter and another for the transmitter. Happy building.
Gene
RF Parts now is $9.95 each ($20.00 minimum before shipping and tax) with minimum shipping for USPS of $9.40. So the best you can do is 3 units for close to $40.00 to your mailbox.
Steve G./N4TTY
Update (the price seems to be skyrocketing!):
MFJ has them for $11.95 each.
Part # 401-6250-1
An additional note is that they no longer trim the coil and have dropped the “-1” from the end of the part number. You’ll have to cut it yourself.
Part # 404-0811 at $22.95 each
Bob,
I just found the Pine Board Project on QRZ and have spent the last couple of hours reading and watching your video’s. I noticed that most of this was produced back in March – April 2017 and was wondering if some of the vendor’s you mention in your video’s have put together “kits” of parts for people who contact them wanting to build this project. I am very interested in doing this and was trying to get a cost and availability idea on the materials before I proceeded. I also am fearful that I will start gathering parts only to be thwarted by not being able to obtain some part that there is no work around for. Back in ’63 when I was ten I wanted to build a regenerative short wave receiver that I had found in a book about radio at the Little Rock public library. I finally talked my Mom into taking me downtown where the stores were at the time. When we showed the man the project in the book he shook his head and said some of the parts were not available any more so that squashed my ambitions for awhile.
You are doing the ‘right thing’ by reiterating in your video’s about being careful and how to deal with the high voltage in this project! Anyway this is Sunday, August 13, so I can’t do much checking now but will do so tomorrow when the vendors are open. Thanks for doing this, it has really got me interested in Amateur radio again!
Sincerely,
James Kidd
N5ROJ
Hi Jim
Happy that you are joining the many that are once again – or first time builders. So much fun. Never worry about parts. Many vendors have the parts. Our parts lists now lists where each part is available. Antique Electronic Supply AES carries the most parts. So, get out the soldering ironn and let’s build!
Thank you
BOB
Bob thank you for this project. I hope that it is a trend and you continue giving us great projects like this one. 73
Hello Bob,
I’m very excited to get going on the pine board project. I just went through my parts box from when I was building audio and guitar amps a few years ago. Work has kind of gotten me away from it, but I think you have sparked something in me. I, like a few of the others really hope you get around to putting up a receiver project that will go with the other projects. Thank you so much.
I’d like to point out that all the schematic and layout diagrams look great and thanks to the person that worked so hard on them. They all download as pdf’s fine except the power supply layout and transmitter schematic. Is it possible to get that fix here on the site? Thanks again.
Buddy from Maryland
I built the early version of the preamp with no EQ. My PS shows close to 200 volts.
The early preamp shows A 33k resistor on the schematic. Bob says PS should be 150VDC out. Not watnting to blow my only 12AX7 how should I proceed?
How do you test the working of the preamp? A 600 ohm mic on the input?
A 5 watt or so speaker on the output?
Thanks for any suggestions.
73,
Bill N4DH
Bill,
Your power supply voltage will drop to 150 volts when all three modules (power, preamp & transmitter) are connected together. So, 200 volts without the transmitter module connected is great. The transmitter tubes (when you add that module) will bring the power down so we need to start big. Your 12AX7 should be fine with 200 volts. I don’t think the 33k is necessary at all – I’m not running one. But, if you have installed it, you are probably OK.
Testing. A 600 ohm mic should be OK. Connect your preamp to an amplifier – not directly to speakers. Plug into a stereo ‘line – in” input or you could use some computer speakers that have a little built-in (normal) amp.
Thanks Gene,
Followed your suggestions. Had an old 1500 ohm impedance mic send plugged it into the imput of the preamp. Used a couple of PC 5watt driven speakers and got nice clean audio out of them. Loud enough to over drive. Was really surprised how nice the preamp sounded. Going to install the two EQ bass/treble pots in while waiting for some transmitte parts. Kudos to Bob for such a nice tube circuit.
Thanks again Gene for your encouragement. And Bob, love the live Wednesday night TV.
73,
Bill, N4DH
I’m down to mounting the 365 mfd variable capacitor on the board.
Anyone have an idea how to hold it down? Gorilla glue?
Bill
Hi Bob
I ran across this last night and just had to comment. I think this is a great idea and want to thank you for designing the project. I do have a couple of questions and comments, however.
Maybe I missed it but I think it would be very worthwhile to explain how the circuits work, why you chose the component values, what would be the result of parts substitutions, etc. I am reminded of my Novice days (1960 s) when I built a lot of Heath Kits. It was fun and I certainly learned something about electronics, but mostly just how to solder.
Now for my questions.
The transmitter circuit looks like the classic “Heising” modulation method. I have always thought that you need to drop the plate voltage with a bypassed resistor to achieve 100 % modulation. Are you able to achieve adequate modulation without this resister?
Also, what level of harmonic suppression are you getting with the “L” matching circuit as opposed to the classic “Pi Network”? I am concerned that the second and third harmonics may be strong enough to detect (and maybe earn some FCC “Fan Mail”)
Guess I will have to just build it and measure the percentage of modulation and level of harmonic suppression.
Thanks again for the neat idea and will continue to follow along.
Dave
Bob, I gave you the wrong call sign of the group of 9 year olds in California. it is K6DGE. Sorry about that. Your pine board project might be a great next step for those youngsters.
Sir,
I have several questions concerning the Pine Board project:
1. I have come into possession of 2 Astatic D104 microphones. One has a two pin plug while the other has a three pin plug. I should like to use at least one of these with the transmitter. Is either usable with this project “as is,” or is there some sort of adapter that must be constructed?
2. If the D104 mikes are not suitable, what recommendation do you have?
3. It seems to me that, if one wished to keep the tube rectifier (I find its visual and emotional appeal much greater than the bridge), that getting a new transformer that is 300-0-300 center tapped would provide the same result. Is my thinking correct? (A new transformer would not be as cost effective, but would preserve the flavor of the project.) What current rating is needed?
4. I would like to wind my own coil for the transmitter. I seem to recall that you had mentioned that instructions to do so would be posted on the web site. Will this be coming soon?
5. I’m fairly completely naïve concerning the proper operation of tube type equipment. I hope that you will spend a bit of time covering how to use it.
6. Looking through old handbooks, it seems that a common CW transmitter scheme used a key in the cathode circuit of the oscillator tube. Is this correct? And is it possible to use this idea to add CW capability to the transmitter?
7. Is the PTT switch you mentioned really a transmit/receive switch?
8. The handbook schematics I have seen (50’s and 60’s) usually incorporate a meter to monitor several parameters. You have not chosen to have a meter (presumably for reasons of simplicity), but would there be any virtue in adding one as I build? In other words, would a meter add to the operation of the transmitter?
I remain quite excited with this project. I am really looking forward to building an amplifier and receiver using vacuum tubes. Perhaps a regenerative receiver would be in keeping with the nature of the pine board.
Thank you for your effort in preparing and presenting this project.
Hi Charles
I think I responded to your questions via e-mail but will cover them here so maybe others can see the answers.
*Yes, the D104 crystal microphone will work fine. No problems there.
* The 6X5 rectifier is a half wave. I do hope everyone has watched George’s great explanation of the D.C
rectifier. Those clips are above on this page. The situation with the half wave is that you will only get around 180 Volts DC and your RF output power will be about 1 watt. I worked 10 stations this morning on our 75 ‘Peanut Whistle Net’ with one watt 6X5 rectifier. Several stations were 200 miles away. I use the bridge to get full wave rectification and this produces around 380 volts to the final tubes and 5 watts out. You can do this with TWO 6X5 rectifiers if you want to stay with tubes. I have set this up so you can plug in the bridge or plug in the 6X5 – paying attention that the center tap has to be removed from the ground when using the full wave bridge.
* We had a video segment using Gene’s hand wound coil. If you can’t find it, e-Mail me I can get that for you.
* I will be doing some things on operation and setting it up soon.
BOB
Charles,
Email me and I will send the coil winding instructions to you.
Gene (W4IQN)
genesmail@comcast.net
Bob:
I’m so pleased that you are using Vacuum Tubes for these PineBoard construction projects. I grew up with Tubes and although Solid State devices are awesome, I still have an affinity for tube equipment, one of the reasons I love my old HeathKit stuff.
regards/73’s
Roy
Kg5dbu
Thank you, Roy. Yes – good ole “valves.”
Hope you are enjoying the project.
BOB
Does anyone have problem with hum/interference?
I have the PS and Preamp built and when I attach the output to a battery powered speaker I get a pretty constant hum. I finally realized I’m picking up a local AM station (50KW about 6 miles away).
It’s present on the power supply output, but hard to see unless you’re looking, which was why I didn’t notice after finishing the PS. I had to use a scope set to AC and me on a mV scale, which made me nervous looking at a 200VDC signal.
The output of the first stage in the preamp shows the noise clearly. And it gets worse if t touch the plate on which all the pots are attached.
Anyone else have a similar problem and have a solution?
Ron, I have not had any hum problems with the several power supplies I have built nor heard of any. I would check the filter caps.
BOB
Oh my. This is a toughie but can be fixed, Ron. I would start by putting a 2.5 mH choice right at the input in series with the grid input line with a .001 from that junction to ground. Give that a try, Ron
For the power supply section I have three 50mfd@450 volts instead of the 20mfd@450 volts will these work with no issues.
Hello Mark
Yes, you will be fine with the 20 mfd @450 volts. I assume you are using the 6X5 tube rectifier not the solid state bridge? No problem. Stay in touch BOB
No im actually useing a full wave bridge and i have 360 volts dc and i dont have 20mfd im useing three 50mfd will this much capacitance be ok.
HI Bob, could you tell me where to get the solid state bridge rectifier and part number. I don’t see that called out on any of you parts lists. Thanks for the great project we need more of these and your doing a great service for us who want to learn.
Steve
Steve,
tubesandmore.com, P-QBR-34, 95 cents
Thanks Bob, I have another question on how you calculated the value for the L-network. I come up with 25 MH for the value of the air core inductor based on the turns and diameter on your schematic and the variable cap 365 pico farad. When I calculate the resonant freq. I come up with 1.63 Megahertz, I must be doing something wrong can you help me out with this.
Thanks
Steve
Thanks Bob, I have another question, how did you calculate the value of the variable capacitor and the air core inductor. I am coming up with about 25 MH for the inductor base on the turns and diameter you have on your schematic. When I use that value and the 365 pico farad variable cap I come up with 1.63 megahertz for the resonant freq. I must be doing something wrong but now sure what. Maybe you can show me how to do it.
Thanks
Steve
I think I just figured it out the variable is from 0 – 365 so it is well within the range to be resonant. Let me know if you have anything to add Bob.
Steve
Hi Steve
Well, honestly, I have these things in a LARGE junk box of 60 years, a wonderful Millen Grid dip meter.
Yep, 365mH it is. Started with the original large coil from KFJ – what use in their amplifiers and shorting turns out until the old Millen tells me it is resonant. Crazy? Yep. But been doing things like this for decades. No slide rules need! Ha. Stay in touch! -Bob
Thanks Bob, I am looking for a good grip dip meter on ebay. Hope to chat with you on 3.885 sometime, I’ve heard you in the evening a few times this fall.
Steve
Regarding the power supply. The original power supply, with the half-wave tube rectifier, had two filter caps. A revision was posted with three filter caps separated by two 1k resistors. Then, we moved to the full wave bridge and continued to use the three caps and two 1k resistors. These 3 cap versions are still posted above.
Then, in the last show, we added the 350 VDC line straight to the transmitter. However, the filter is now back to two caps and the resistors and configuration have changed once again. This version of the power supply is not posted and the clips from the show do not adequately show the values and configuration.
I am still using the three cap two 1k resistor configuration with the bridge. My output voltage at the end of the filter is nearly the same as the 350 VDC transmitter line at the beginning of the filter.
Can someone post the latest version of the filter section so that I may once again revise the power supply to meet the current design. I love the project and I have learned much. However, I am a little confused as to how we went from what is posted to what was demonstrated in the last show.
Thank you, Jim
Hi Jim
/Users/bobheil/Desktop/PS revised layout Bob.pdf
This is the power supply that I have been using the past couple of months and is THE answer as it provides two voltages, +350 for the transmitter module and +170 for the pre amp. Two 20 mfd caps and a pair of 33K resistors. The P-QBR-34 bridge is from AES and only costs 95 cents!. This works well and increases the power output of the 6AG7 TO 5 WATTS. If you would like full diagrams – please e mail me bob@heilsound.com. The Pine Board with full diagrams, etc. will be the feature cover story in the January QST. Stay in touch, Jim
-Bob Heil
Did I read somewhere there was a mod to the power supply that utilized two tubes instead of the bridge rectifier to give a 300 volt full rectified output?
Thnx,
-TAC
KC8SES
“We started the Pine Board Project with a 6X5 vacuum tube rectifier to change the secondary AC voltage of the transformer to D.C. That tube is a half-wave rectifier.”
A 6X5 is a full-wave rectifier – see the RCA Receiving Tube Manual – and your circuit uses it as a full-wave rectifier.
yes but to use the 6×5 or even the 5y3 with a transformer with an extra5 vac winding you need 250vac on either side of center tap, not 125vac either side of center tap. he get full wave with a diode bridge that does not need the center tap so yes he gets full 250vac output voltage by using the WHOLE HV WINDING thus disregarding the center tap. remember tubes need that center tap. also be mindful you will need also to increase the output of the transformer on either side of center tap as you have voltage drop across the rectifier tube as well, these are all things you must take into account. the transformers are available new from hammond via at AES. http://www.tubesandmore.com. they are around 59 to 69 USD.
Hi Bob,
I have been calling and finally emailed MFJ about the MFJ 404-8011-1 coil for the Pine Board transmitter. Apparently they did not produce this one. they have the 404-8011 and we’ll have to cut it to the size we need. With shipping, handling and tax it is $35.95.
The following is a copy from my ticket I submitted about the 404-8011-1.
Date: 2017-12-04 15:15:12
Name: Richard
Message:
actual part number is just 404-0811, originally we were going to make a coil specific to the pine board project, but we felt too expensive so just decided to let the ham nation folks cut it down themselves. thanks for your business.
That is true. MFJ has made the 404-0811 available to all. You will cut it down to 41 turns and you are in business.
How are you keying the transmitter on and off ? I see a switch on the picture of the transmitter but it is not on the schematic.
We had two shows about keying the transmitter AND built the antenna relay. Check those replays. LOTS of info…
Stay in touch, please
Hi Bob. Love the project! Have you any thoughts about plans for maybe a 25 watt linear amp that would allow you to drive an amp like an SB200 or SB220? That would be awesome.
Any thanks again and keep up the great work. BTW, I have one of your Heil Classic microphones and i love it.
73,
Dave, WA4LLR
Hi Dave
We are working on a design for a small 30 watt amplifier. I can drive my pair of 3-500 to about 60 watts with the 5 watts. Try it. Stay in touch… Working on the amp project
they have a version of the 6L6 gc that will do 35 watts max on plate. also some smaller 6 volt sweep tubes that can easily do this too.
Bob,
Great project. At 72 years old, I wish I would have built something like this when I was a novice in my teens. I went to TubesandMore.com to order the power supply kit. It shows that it is out of stock. Do you have any idea when it will again be available?
Bob,
I wrote that the power supply kit was unavailable. But I went on line again the next day, and it was available and I ordered it. Again, thanks for a great project. Jim WB8SZJ
Bob,
I contacted onlinecomponents to purchase the 2.5 mH RF choke. They have it for $1.59. The problem is that they have a minimum order requirement of $50.00. They did not know about your project when I asked them, so please advise me how to obtain the choke from them, or another source.
Jim
Put 2.5 mH CHOKE IN GOOGLE…. ALL KINDS OF PLACES FOR THEM.
YES, AES RAN OUT OF PARTS – BUT FRANTICLLY RESTOCKING…..TOLD THEM THEY WOULD GET SOME ORDERS… HI
SO THRILLED WE ARE HELPING SO MANY GUYS
Bob,
I see a piece of coax is being used in the pre-amp from the input jack to the 6 lug terminal strip. Could you please talk about this? What kind of coax? Does the shield represent the ground track on the schematic? Is it grounded at each end?
What a great project!!! I never had an Elmer as a young ham — I am so happy that you have become my Elmer!!
Thanks, Jim Hunter WB8SZJ
Hello, I just finished the Power Supply. I made the origional design, I like using tubes.
I tried it out, but had zero output but the light was on. After checking, I had wires on the wrong socket number. I switched them, and have 205 v on B+ and the light is on also.
Mt wife gave my a early Christmas present, a 3d printer, so i printed my own brackets for the fuze holder and switch. I will be printing more brackets for the next phase.
Will start on the pre-amp next.
Great project , thx.
Vince
KD8ULR
Well how cool is that, Vince. PELASE stay in touch…send pictures….. let’s talk about your work
Bob,
Thanks for all you are doing inspiring us to build this great project!
Could you help explain how we could use an oscilloscope to test and/or monitor the output signal?
I am not an EE, and am afraid that I might blow up my oscilloscope if I attach the leads to the output, given the high voltages being used.
Also, if one wanted to use an ammeter to monitor the final plate current, how would one hook it up into the circuit without affecting the output?
Thank you again!
Pete
KD2OMV
Hi Pete
We had several shows about a small adapter to get a signal into the scope. Look at the list of all the shows.
Let em know if you can’t find that
Hi Bob!
I assume you meant the HamNation shows….I searched back a couple years, but am having difficulty finding mention of an adapter for an oscilloscope. Each episode is over an hour long…
Is there a way to narrow down the search or could you help me zero in on where you describe that device?
Very much appreciated!
73
Pete
KD2OMV
I’m really jazzed about the Pine Board project after seeing the QST article then watching the above videos. I might have everything I need for the power supply from my (non-)junk box, but am wondering about the voltage ranges that the transmitter and preamp would be happy with. It looks like the preamp is looking for around 180 VDC and the transmitter around 350 VDC, but I’m wondering how much I can vary from those voltages with the circuits in the QST article. I’m also wondering about the B+ current draw for each of these stages.
Any help would be muchly appreciated!
73 – Brian, NC4BT
I want to build mine into a metal case any thoughts?
Thanks,
Big Mike N8FWD
I just called aes. The power transformer is on order from Hammond. Sounds like they won’t have it in until Jan 12-13 per the customer rep, but they are taking orders.
Hi Bob
Just wanted to say thanks for designing the pine board project. I just built my power supply and tested sat. B+ about 400 Volts DC and pre-amp B+ 200 Volts Dc. I have a question on the ground. Why are we using the equipment safety ground for the power supply ground. why wouldn’t we use the neutral. Just wondering.
H.A. Hawkins KD0ZLV
on the field strength meter the gauge, is it of the AC type or d/c type. I don’t want to guess.
It is a DC meter movement. 0-1 milliamp or 0-500 microamp should work fine.
Allen, W9DZ
Now I called mfj and the coil is back ordered. I think we’ve blindsided these companies with our demand! ????
Hi Dr. Heil,
On the Pine Board Transmitter the parts list calls for a 2.5mH RF Choke from radiodaze.com. After contacting them they say: The mfg stopped making them and has no plans to start making them again. We are looking for other sources but it will taker some time to track a new company down and make these.
Do you have another source for these?
Thank You in Advance,
Gilbert
N6YBX
I bought item number 171225855915 on ebay, and am waiting for it to come in. I know its a pack of 4 but it seems they are scarce.
Hi Chris,
Thank you for the info. I noticed that this is a 4 pie choke and the plans above use a 3 pie choke, what would the effect be of using a 4 pie vs a 3 pie?
Appreciate any help.
Gilbert
N6YBX
does not matter if its 3 or 4 pie. just the value and current rating.
Thanks for joining us building the Pine Board. The neutral you speak of is one side of the AC line?
I always want the ground. It’s the third pin ground that actually connects the ground of the AC fuse box to an 8′ copper rod.
Sounds like you have the power supply happening. Look forward to hearing your transmitter results
I just saw the article in QST and am looking forward to building this project. Before I start I have a question about the relay schematic. Where can I find a good quality readable copy of the circuit? The one shown in the video is difficult to read and identify the details. I don’t want to hook it up the wrong way. Thanks.
Hi Steven
Gateway electronics in St Louis has the ‘ice cube’ relays: 110 v, 24 v, or 12 volt. Your choice of how you want to control that main relay.
Gateway-electronics.com. They have a lot of other things, too!
Another question about the 2.5mH choke – what toroid, wire & how many turns would be required to make the required induction?
Thanks
Dan
WD4IRK
Hi Dan
Richard and I are working on that as well as scouting sources and it looks like we will have a good source in a few days. Check back here for updates.
When I finish this project (or maybe as I’m doing it) I want to learn how to use my tektronics scope to look at waveforms and learn about oscilloscopes. Is there anything I need to know about using a scope and 10x probe. What do I need to avoid to not fry the scope? I’ve been keeping my safety in mind, but I’m worried about scope safety.
Bob: The Pine Board TX is a great thing for club projects, since a lot of newcomers will have the satisfaction of building and using something that they constructed with their own hands. This will help them understand that ham radio is not just limited to purchasing the latest plastic-cased transceiver.
The pine board TX with it’s great audio is good, but what will a newcomer with an SSB transceiver do to “hear” the good AM sound? Will a “pine board receiver” be next? What would that be? Regenerative two tuber? One could convert an old “all American five” AC/DC radio to handle 75 meters, if there are any to be found. Time to think about a solution to complete the “other half” of your great project.
73, Perry W8AU
Bob –
I’m just getting started on the Pine Board project and I’m looking forward to it. I’m in the securing parts phase. I have most everything with a few exceptions. Thanks for doing all of this. I have a couple of questions, because I’m a bit confused.
Question
I’m trying to secure the right parts and make sure I understand the right capacitor values and conversion. As an example, on the 3rd project on this site you list two parts as
1 – ceramic disc capacitor 0.0047 mfd
2 – ceramic disc capacitor 0.001 mfd
On TubesandMore their corresponding kit is here. https://www.tubesandmore.com/products/mic-preamp-kit-ham-nation-bob-heil
They list their corresponding parts as 470 pF and 10,000 pF
470 pF. – https://www.tubesandmore.com/products/capacitor-ceramic-disc-2000v.
10,000 pF – https://www.tubesandmore.com/products/capacitor-ceramic-disc-100v
So 0.0047 mfd should convert to 470 pF and 0.001 mfd should convert to 10,000 pF. Is the little m a mill 1E10-3 or a micro 1E10-6? I’ve read that some sites use m interchangeable between u and m (micro) https://www.westfloridacomponents.com/blog/is-mf-mfd-the-same-as-uf/
On top of that the example above is .0047m to 470pf isn’t that a conversion of 1E107 off by a factor of 10x.
Did I confuse you as much as I have myself. Sorry.
My other hopefully easier question is when securing parts do you have to be exact in the specs? As an example I saw some 100mA meters for project one listed as 1K and 2K internal resistance. Does it matter? Another example is if you need a 470pF, is 600 pF close enough. How do you think about it. I’m hungry to learn hopefully you can help.
Thank you very much
Jay
AJ6AZ
When I was a novice 40+ i was very discouraged by the plans for Novice transmitters that were in the ARRL manual. If they had the pineboard back then I think my Ham career would have been different.
Thanks!!!!
They are out there! Heard my 1st Pine Board station tonight, and worked him. Glen, N4AK, over in Sunset, SC at an S9 for a brief time. Me? I’m over here near Charleston, WV. Not bad for 5W! Not bad audio either from him. A tough copy at times, where I had to goto 2.5kHz AM narrow, but a 100% copy nonetheless. Can’t wait to work more Pine Board Project stations out there!
Phil, N2MDV
That is so cool! Thank you for sharing with us.
Hi Bob,
I’m a new General Ham, call sign WD2ORG, and I’ve been looking for an AM transmitter project for some time to broadcast AM radio in my home to the antique AM/FM mono and MW/SW tube radios that I’ll be restoring once I build up a sufficient parts and equipment inventory. It’d be really nice if I could tune in music from the 1930s to 1960s and make the radios (and me) feel more at home with our shared vintage, as well as test their ability to receive hi-fi mono signals, but none of the AM stations near me have that kind of programming. Your Pine Board Project TX would be the answer to a dream if I can adapt it to transmit recorded golden-age-of-radio music on the AM broadcast band (per Part 15, of course). Can it be adapted with a different crystal perhaps to transmit low-level mono signals in the broadcast band, and would the bandwidth be high enough to make it sound like the hi-fi AM signals one could receive before FM became popular in the 1950s? Thanks for a great project!
Hi Bruce
Our next mod/addition will be to use the entire 8011 coil from MFJ, change the variable cap and crystal to 1.985 and the Pine Board works beautifully on 160 meters so there is no question about your needs….larger coil and cap to resonate at your needed frequency…
Good luck. Just make sure you are transmitting into a dummy load.
BOB
AES sells a kit just for that. there are plans online to wind your own coil for that kit so you can run it on your SW radio or am radio. signal stays near the home. plans to add a audio preamp as well to that circuit.
I could not find a substitute for the 2.5 mH chokes.
I did find this:
Mouser #: 542-5900-222-RC
Mfr. #: 5900-222-RC
Desc.: Fixed Inductors Fixed Inductors 2.2mH 10%
$ 1.63
I just received my RF chokes today. Here’s the info from ebay. Kinda pricey, though. Good luck!
4pcs 2.5mH RF Choke 0.17Amp 4pie
Item price $22.00
Quantity 1
Item number 171225855915
Shipping service ePacket delivery from China
MFJ can help us with the 2.5 mH choke.
MFJ will supply the tax coil and we will soon have a show in last of February or the first of March on how to use ALL of that coil, tapped for 160, 75 and 40 meters so don’t cut it off just yet! The Pine Board is a stellar performer on 160 meter AM.
BOB
Do you have an MFJ part number and price for the 2.5mh chokes?
-Mark
MFJ 2.5 mH choke part #: 401-6250-1 $11.95 each.
I am looking for the updated layouts and the schematics especially the relay board and the updated transmitter. Any idea of the time they will be published on the site?
I saw the video for the CW jack add on, unfortunately my screen resolution is not good enough to reproduce it. Can I get a copy of the
schematic of the transmitter with the CW option? It would be nice to have a pictograph layout as an alternative build. Maybe an:
A) AM only
B) AM &CW
Thanks,
Terry K5ZBY
Hi Bob,
I found an HV transformer in my junk box 350-0-350, which results in about 450V out when rectified and filtered. Would it be appropriate to use this as B+ with a heavy duty 6V6, or would it be better to tap it down to 350V per the article?
Thanks for your thoughts Stew Bowers WB6FBB
use a 5y3 tube if you have a 5 volt winding has more voltage drop than other tubes do and do a Pi filter choke filter circuit. that will drop it alot. also you can do some OD series gas regulator tubes that will help the cw note in cw mode as well.
Really looking forward to the schematic for the AM- CW combination transmitter. This project fits in very nicely for my return to being on the air and working qrp both voice and CW. It is great to see projects like this and going to be a lot of fun. Looking forward to even more projects to build.
Hi Bob,
Allan KV4T and me KW4OB will start on this project tomorrow. I have all the parts.
But Allan also needs the CW extension. Maybe me too for Hellschreiber. On the video the values of the parts are not readable.
I guess you split the capacitor in half, keep the resistor and add another 2.5mH choke, correct?
Or please post the schematics.
You can review my QRZ page, BTW the same CE setup as in the back of your videos.
73, Ingo
Dear Bob ,
Please help us find a substitute for the 2.5Mh choke coil and for the large air core coil. None of the radio sites carry the parts anymore.
Please advise,
Thanks,
Kevin Grucella
Malta, NY
518 899-4238
Super informative project. This has really helped my understanding of tube circuits. Seems like so many possible other combinations of added capabilities to this entire project that the learning would never stop. Looked at the Transmitter circuit for CW and AM combination and realized that the key will be at HIGH Voltage of the cathode. OUCH if not handled properly. Maybe a 6.3 volt cathode keying circuit to keep the key at a low potential using the 6.3 volts available would be a nice addition so our new hams can be a little safer using a straight brass key.
Maybe another nice addition would be to replace the key jack with a non-shorting jack and make the CW-AM switch a double pole single throw and use the second half to short across the key jack in the AM position allowing the operator to go from CW to AM without unplugging the key all the time. Just a couple of ideas to ponder for all building the project.
I am really looking forward to more additions and projects. This is Super Project and Thanks Bob and to all who are supporting you with explanations, drawings and everyone’s time to make this happen.
Back into building my own equipment and working QRP. Clark KG9FM
.
My loose can if marbles upstairs just rolled to the obvious. The key is at ground potential so ignore my marbles about the key being hot since it is at ground potential in relation to the world. My mistake and it sure is an obvious one.
I just found out about your pine board project after discovering Twit on my Ruko. I am an old man trying to keep his mind active and find this project very interesting. Is there a single parts list for the entire project so I can get the parts ordered?
Thanks
Allen N7LVS
That’s wonderful, Allen!
The parts lists are in each section since we built the entire project in stages.
I’m about to build the mic-preamp and I noticed that the bright/flat switch is on the high voltage side of the coupling capacitors between the 12ax7 tube stages. Could this be a shock hazard since this would present a few hundred volts on the front panel switch in the event of a switch malfunction? Ouch! And if the front panel is wood or plastic the fuse won’t blow.
Wouldn’t it be safer to install the switch on the low voltage side of the coupling capacitors where there is usually less than 1 volt?
Don KZ9S
Hi Bob,
Great fun project. Just getting started with it and have all the parts. I have one question, any recommendations on the best way to cut the MFJ coil down to the 41 turns?
Thanks, Vince K6VOH
I am having a problem with my power supply. When I flip the switch on, the pilot light glows and the tube begins to glow, but them in about thirty seconds the fuse blows and everything goes dead. I have checked for shorts but are not able to find any.
I suspect that the fuse that came with the Antique Electronics Kit (P-BH-PS) is too small to carry the load across the primaries in the transformer. When set up as depicted in the schematics and the pictorial diagrams, the fuse is on one leg of the 120/ transformer primary, with the switch on the other leg. I am at work and do not have one of the fuses with me, but I do not think it is as much as one amp. I realize I could reverse engineer the circuit using my volt/amp meter, but wondered if someone could shoot me the numbers. Specifically I need the amperage across the 120 legs and transformer primary windings and a suggestion for the proper amperage fuse. Thanks.
Bill Brower
I had the very same problem!!! I had to replace the tube. The heater section worked fine, but the diode section had some sort of damage that caused a short as the elements heated. Another member of our local radio club tested my tube, determined that it was shorted and supplied me with a new tube. Worked like a charm!
Can’t answer your specific questions about the primary current or the fuse. I ‘used up’ all the 1amp fuses that were in the kit and also all the fuses from the local ACE hardware store trying to resolve my problem.
Good luck!
Ok. Next a vfo for this great project. Any suggestions for us beginning builders and how to accomplish it. Maybe I am just getting to enthusiastic about this whole project. Guess I have been lead to the water trough, learned, and cant stop drinking. I am really grateful for finally learning some about how these things work. I have a salvaged Heath HG-10b (2 of them and now rebuilding with help) and interested how to make it work as VFO for this transmitter on 80 and 40 meter bands as others may also be interested in adding a VFO.
Sometimes my enthusiasm gets overwhelming and I ask to much but this has really lit a fire. Thanks to all.
Clark KG9FM
Bob
Working on psu using a full bridge rectifier. I have checked my wiring at least 4 times however the 3 amp fuse keeps blowing. The pilot light works as I hooked everything up in stages. However when I connect the red wires from the transformer to the 2 outside legs of the rectifier and plug in the power the fuse blows every time. Any advice would be appreciated
Art N2AJO
Art
Make sure the center tap is not grounded. You then should do a test on the diodes in the rectifier using a simple ohmmeter to make sure they are all ‘going the correct way’. The only other situation would be a shorted capacitor. In any circuit, you will want to go through part by part as a process of elimination.
First, measure the AC to the transformer with nothing connected. Be sure it is okay. They connect JUST the bridge. If it is installed properly and the fuse blows – you have a bad rectifier. If that is still good you do not have a blown fuse, connect the first the capacitor then the second, etc. That is how we test a circuit…. piece by piece. Let me know how it all turns out.
BOB
HI Bob:
Just want to tell you what a blast this whole project is. For the past four Saturdays three fellers and I have been working on this, and it is the highlight of my week. When we all get these up and running, we’re going to add a regenerative receiver project, tapped off the same power supply.
I might want to add that some kind of plate current meter would be nice. It would be really educational to demonstrate that the max RF output occurs at a plate current dip…and why! We can also demonstrate just how the L/C ratio affects the LOADING.
Thanks for this wonderful idea….this is what ham radio is all about. Hope to see you on Skype again!
73,
Eric and the North Pole gang at KL7EX
Maybe this has been covered before, if so I apologize. I am building the power supply with a diode bridge (adding a 5 Hy choke after the first filter cap) and will then voltage divide three different B+ voltages. My question is…looking up the specs for the tubes in the audio preamp and the transmitter, they are all good for 300V (or more in one tube). Is there a reason you wanted much less on the preamp plate? Just curious.
Hi Gary
RE: Different voltages….. I like to decouple the B+ lines from each section of a circuit rather than drive them all from one 300 volts ( or thereabouts). There really is not a problem running all of them from one source but hey – what’s a couple of resistors? ON anything audio, I also like to add another capacitor – just for insurance of taming that d.c. voltage. 20mfd @450 or so. It’s not necessary but doesn’t hurt.
Hope this helps
BOB HEIL
Hi.
I am a Swedish HAM and really enjoy watching Ham Nation.
I have not started building the Pine Board but I am really interested on doing it.
I do not know how many wieers Ham Nation has overseas butIthink you should point out that the power supply is made for 110 V AC.
Here in Sweden if Iput everything together with your component all of the voltages would double since our wall socket has 230 V AC 50 Hz in them.
Kind regards
SM0YNP Erik
you maybe could find a european transformer of similar spec or see if hammond has a 250 volt center 250 volt power transformer with a 220 volt input. I think AES has them. look under guitar amp transformers. that way you could use a rectifer tube instead of the bridge.
Erik
tubesandmore.com carries a line of 230volt input power transformers for guitar amplifier.
also hammond can supply you with same.
best regards,
Sean
Hi Bob,
Several Questions 1) is there an antenna tuner in the works. 2) any clues to what tube will be in the small RF amplifier and what voltages it will need. 3) can a meter and how can it be added to the transmitter for the plate current to be measured. 4) can you show us how to design an rf output filter section. 5) can 6J5 tubes be used in place of the single 12ax7 and last I have a 250 volt center tap and 250volt transforer with 6 volt filament windings and a 5 volt winding. also have a type 83 mercury vapor rectifier tube, will this work? also are the chokes critical in value. I have 2 large coffin box cabinets from the 1920’s that had radios in them. thinking to mount my units inside with a phenolic faceplate.
Thanks,
Sean
Bob,
you wouldmaybe be thinking of using a 6L6GC or 7581 tube in the 30 watt final amplifier? plate dissapation is about right and they seem plentiful and available and was used around the time these types of circuits was built. also I found a 6sn7 and a 6SL7 dual triode and octal socket in my junkbox. its a 6 volt heted dual triode of similar specs to a 12ax7. I also got some 12au7 and 12at7 tubes. would either of these work. I have the correct voltages from my power supply I completed today . the 5y3/ tried a 5u4 as well. works well and I tried it with a type 83, i prefer the mercury vapor glow but the 5y3 and the 5u4 seems to do the job. looking forward to the preamp. I got all the parts from my junkbins so far. cost has been ZERO USD. Thanks for putting the fun back into radio.
Getting started in a very thought provoking project. I can’t wait to complete it. I am just a beginner, my electrical circuit math is poor at best. My Question is: What wattage are the resistors?
Hi James
Thanks for your note. Most resistors are 1/4 watt but the two 33K in the power supply are 5 watt along with the screen resistors are 2 watt.
Hope this helps
BOB
Greetings Mr. Heil,
My name is Ron (WA8YIH) and I recently completed my pine board power supply. While waiting for a few parts to arrive, I am beginning to build my transmitter. I am planning to make this work for 6-meters first for a local 6M AM boat anchor net. Instead of using a band switch, I am planning to use removable coils (for now…). Using the suggested coil diameter and TPI, how many turns would I need for 6M? Is there a magic formula for coils (I see several out there), or will I be close enough by simply using a multiple of the # of turns used for 80/40 and simply divide to get a ball park number of turns?
This is a wonderful and educational project that you and the other hams have put together. I am having a lot of fun and learning a lot.
Cheers,
Ron, WA8YIH
I am using plug in coil forms made from octal tube bases with lightly machined black pvc as extensions for the length. also have some very nice vintage 3, 4 and 5 position ceramic bandswitches. i am going to build 2 or 3 transmitters myself in different configurations. this thing is fun and ADDICTIVE. THANKS BOB, THIS IS GREAT.
Bob Heil has started me on a great journey and I have looked for more information. I have found this site to augment the great work that Bob has started for all of us to learn and build. The site is http://faculty.frostburg.edu/phys/latta/ee/ee.html I want to thank Bob and all those involved in the Pine Board project for getting me back into the Hobby with enthusiasm that I had lost when my Mentor became a Silent Key. Please keep the projects coming at us.
Thank You, Bob
Does the impedance of the coax for the pre-amp matter? If so what should it be?
use shields audio wire, just buy a cheap shielded av cable and cut what you need from it.
Hi James,
Thanks for your note. Most resistors are 1/4 watt but the two 33K in the power supply are 5 watt, along with the screen resistors that are 2 watts.
Hope this helps!
BOB
Hi Bob… Your project is one of the best ideas I have seen in years. Been licensed for 57 years and this reminds me of equipment I built in the ’60s. I have believed for all these years that you could not modulate and oscillator without getting FM. Obviously this old dog has learned a new trick– a revelation.
My question is: have others tried slightly higher powered tubes? Seems like a pentode with a suppressor grid is necessary. Apparently an 807 would not work, but something else like a 1625 (has a suppressor grid) might work. Modulation with a 6L6 seems like a good idea if all parts changes and required voltages are made.
What have you observed re: the suppressor grid and what other tubes have been used in an electron coupled oscillator like you are using. Heard you many times lately on 75M. I have several old boat anchor rigs. TNX Mike K8WEU.
Hi Mike,
Thank you for your nice note. There are many combinations of tubes that can be used. I selected these because it follows the 1954 ARRL handbook CW rig. I knew it was a proven circuit and there are many (over one hundred), so wanted something that would work first time out.
Thank you!
BOB
got my power supply built, i actually built 2 of them. built yours as designed and built one identical except used a transformer with 250 volts ac either side of center tap and a 5 volt rectifier filament instead of ac. as you probably know the 6×5 has a reputation of shorting and eating transformers. and alot of folks like the look of tubes. that is the reason I went with the other transformer on the second one. I use a type 83 to keep the voltage drop across the tube in check. to use a 5u4 or 5y3 simply use a 275vac either side of center tap. with the 275 vac trans former I was able to also do Pi filter ( cap input, choke, cap output filtering) both transformers I mention cost around $60 BUT AES keeps them in regular stock.
As an interesting side note I have found series string 25 and 35 volt filament tubes and using voltage doubling rectifer can build the power supply, preamp and transmitter to the same circuit but without the need for the power transformer and get the same output. I have the prototype of it under construction as we speak. saves the price of the transformer and the tube price is a little lower as well. uses OCTAL tubes still save the 12ax7.
again thanks for getting us all back into building. no more appliance operating for me. my factory stuff is going on the shelf.
For you guys who prefer octal tubes. I have researched and found they make an adpater to use a 12sL7 octal tube in place of the 12ax7 in guitar amps. that said I have tried a 12sL7 in my preamp by changing to an octal socket and yes, it works great. also not the 6v6 and 6ag7 tube specs, not althought the 6v6 has an internal connection to cathode , it can be used to replace the 6ag7 if you change the connections. this works because you are connecting the cathode to ground on the 6ag7 and the screen to ground as well, in the 6v6 its already ties internally to ground with the cathode and it has a higher plate dissipation, that said if you do this, you could technically put a 6L6 in its place if thats all you had.
correction to that, I ended up with a 6SL7 as bobs 12ax7 filament is wired for 6 volt parallel and not 12 volt series.
Sir,
I would be interested in the values you have for the filter caps and choke (as well as bleeder resistor.) I’m deciding on a design for a 5U4 based power supply using a 375-0-375 transformer, and would appreciate the benefit of your knowledge.
Thanks,
Charles Wells AD0UY
5 to 10 henries and 10 to 20 uf at 500 vdc (600 prefered)
if you do not have a 6v6 tube, you can use a miniature 6aq5 tube in place of the 6v6. specs are identical but in a miniature tube. also as for the 12ax7, if you prefer an octal tube in its place its not a 12SL7 you would use here but a 6SL7 as Bob did not series the filaments in the 12ax7 but put them in parallel. as a side note you could do this circuit with a 6aq5 in place of the 6ag7 or better yet a 6bq5 as its secs are nearly identical to a lower end 6L6. I am also starting to build miniature tube version of Bobs circuits without any modifications. I will check the rf spectrum analyzer my friend has and see what the output looks like.
for those interested, I have researched many circuits and asked many a person and a 1mh, a 2mh and a 2.4 mh choke will work equally well in the same circuit to choke the rf. the 2.5 was more common and popular amongst hams. was also a common milsurplus part at one point. thing is I tried it and it works, also you can use the smaller cheaper 50 ma chokes if you can find them in your field strength meter and in the mic input and save the 150 ma and larger chokes for the rf section.
and yes I rebuilt my second preamp with a 6SL7 tube and it works just fine if you want to stay with octal tubes or if its all you have. remember to just make the right connection to the right pin. its specs are super close to the 12ax7 tube and the amplification factor is so close as I said they make adapters to replace 12ax7’s with so you so not have to mod the chassis on alot of preamps and such. also for those who want to use a tube rectifier, remember you will need a transformer with a little more voltage than 250 vac either side of center tap ac. you have to figure in voltage drop across the recitifer tube. i have upped mine to 275vac either side of center tap and even 300 volts either side of center. as a note look at guitar amps even old console stereos with tubes and old electric organs and at tubesandmore.com for replacement transformers for tube amps, our requirements are minimal and those replacement transformers are sometimes cheaper than a factory hammond. also they carry alot of CE branded transformers, they are imports but often 10 to 20% less.
I have even found good transformers in old pa equipment and test equipment.
Sean Ross
From the first, since I was late to the party, I changed the layout a little to accommodate 160M.
I ordered another xtal for top band. I used a octal socket for the crystal. That way I have a place to store the 2 extra xtals. I used a 6VAC coil relay for the antenna transfer relay. That way I already had the voltage on the board. Electronic Supply in Kansas City had over stocked 6VAC relays some time ago and has plenty in stock. I need to refine my layout a little. I will incorporate PTT in the next layout. Good point about the bandswitch.
I use a dpdt s switch to change the crystals as well using an octal socket to hold my crystals. changing to a dp 3 throw rotary switch so i can select either of 2 crystals or the circuit in place of the crystal to allow a dds vfo kit to be used as well.
I built a nice audio amplifier out of this circuit by using the power supply and preamp and removing the 6ag7 and all the rf components and wiring and replacing the 4 henry choke with an audio output transformer and connecting a 4 x 7 speaker. I going to use it with my crystal set and my 1 tube and 2 tube radio set . I also used the preamp by itself on a crystal set as a headphone amplifer. not blasting loud but it puts out the sound. I used an output transformer on it as well on the preamp I used as a headphone amp so i could use low impedance headphones.
This unit has a lot of potential.
looking at the 6eu7 tube. it is also a twin triode and has the SAME exact and mean save exact specs as the 12ax7. it is 6 volt so no need to parallel filaments and only change is to rewire the tube socket to the pinout. and they are american made.
a 6F5 tube is the exact same as a section of the 12ax7 tube. has an amplification factor of 100 same as the 12ax7. you would need 2 of these and remember they are octal and need an octal socket. also the grid connects to the top connection, not the plate. I am building my next prototype with 2 of these.
I have making a new pineboard with my homemade plug in coils that use the same variable caps and tank circuit. cost per coil and form was around $4 including the wire. also I have made a long coil on garolite (expensive) and sanded black pvc that fits in place of the AirDux style coil. cost per coil on the garolite coil was $15 including wire and the metal lugs on the ends. black pvc coil and enameled wire was $5. keep in mind the long coil is for 160/80/40 meters. a source for 365 pf variable air caps is cheap old tube type ac/dc clock radios that no one seems to collect. they also have a good source of tubes and audio output transformers as well for further projects along the lines of this series. 2 of these old clock radios can give you 2 tuning caps . also the primary of an old output transformer can be used as the modulator choke, QST has had articles on this and I have tried it and it works just fine. these transformers are in said clock radios.
Another good source of parts is the old ft 101 series radios. they have filament, use solid state rectifiers and have as a side benfit a HV teminal and a low HV terminal, you can run this rig off the low HV terminal and run an added amplifier off the Hv terminal itself. also a good source of 300 pf variable caps and I think a slightly smaller 160 pf or so variable cap plus plate caps an other HV caps.
Coil data is as follows for 80 meters using 365 pf capacitor its 41 turns of #24 wire on a 1 inch form, 40 meters its 20 turns. I am working on octal plug in coils using pvc and tube bases that use coils wound for the 365 pf capacitor as well. also working on a vertical tapped coil as well. also looking at the plans from an old lindsey Publication showing a gingery coil winding machine that allows you to wind latticed pie wound sections to make 2.5 mh rf coils. i found a source for the ceramic form. the form is a standoff and use brass screws and solder lugs on the ends, simple and effective
if you do not have a 6v6 for the modulator, you can use a 6l6 in a pinch as both are beam power tubes and both have the same base pinout.
If you do not have a 12ax7 also you can use (2) 6av6 triode tubes, a 6av6 is half a 12ax7 and has identical specs. also (2) 6av6 tubes seem to be alot cheaper than american 12ax7 tubes and alot more plentiful in parts bins. also since a 6L6 has the same exact basing as a 6v6. you can put it in in a pinch in place of the 6v6 if you do not have one.
I have ordered a coil winding machine from China with turns counter and 1000 ceramic forms, total cost was $175. have the wire also , it was $20. I can now wind all the 2.5mh rf chokes we need. I am doing this at actual materials cost plus 10% for my time plus actual shipping cost at lowest rate.
I will be glad to offer the coil data here or in any form we can agree on. will have data on the airwound coils, 3 ways to make them plus plug in coils and how to make them. all materials used are available now and easily gotten. will list source of parts as well to do all this. will make it alot easier to build for those with not many resources at hand.
Sean please contact me regarding 2.5 mh rf chokes. tnx, 73. Bill
what can i do for you? I maybe releasing some of my NOS 2.5mh rf chokes soon.
As soon as I prove my pineboard built proper and to original specs and show the different coils working proper. I will be glad to offer the same kits as AES but more complete with rf choke and tubes and bigger pineboards plus coil, if you prefer to order without the prebuilt coil, I will be glad to offer the forms, wire and complete instructions to build 2 or 3 different coil designs that work, will also plan to offer a pie output with the added 365 pf variable capacitor or a dual section 365pf variable capacitor. as for using and audio output transformer in place of the choke in the transmitter, I am thinking to use a headphone jack on the 8 ohm side of the transformer , so you an use headphones to monitor your transmission audio. I have yet to try it but I think it would be feasible, something to think about.
I am interested in your RF Chokes Sean.
I’m interested too, but need contact info.
Steve G./N4TTY
I have all of the parts to build bob’s transmitter in a complete kit same as AES as of now. Since they are sold out, I would offer the transmitter kit. would be $45 more than AES but includes tubes and rf choke and the larger nice milled pineboard. I am making zero off this at this price. just my cost.
here are 2 articles on winding your own air dux style coil.
http://www.ad5x.com/images/Articles/CoilRevB.pdf
https://www.eham.net/articles/23124
Also in case you do not have or cannot find a 6v6 reasonable. I have tested a 6w6 and it is a direct plug in for the modulator tube. They have the same 7AC octal basing as the 6v6 but it has about 1.5 watts less plate dissipation but the voltages are the same. considering what were are using them for here, they will do just fine. AES has them for $3.90 . I think they should include these with the kits.
Has anyone noted the power supply voltages with the XMIT switch on/off? On my build, using the original (non-bridge) power supply, the supply voltage drops from ~175 with the XMIT switch off, down to ~100 when the XMIT switch is on.
Is that normal? Nothing seems to be smoking or melting, but that seems like a big voltage drop!
you need a transformer with 250 volts either side of center, however note you have voltage drop across the tube, you need at least 600 volt center tapped or 300 volts either side of center to use a tube rectifier instead of a bridge.
Thanks for the response Sean.
Are you saying that with the higher voltage power supply there will not be as much of a voltage drop?
yes, do not exceed the rated output Bob has designed, you need the correct transformer as i said to get the proper voltage with tube rectifier. you need a transformer with at least 250 volts either side of center that is ac voltage, when rectified it will be higher and dc, problem is the voltage drop across the rectifier tube. also if using a 5y3 or 5u4 rectifier , you need a 3 amp rectifier winding as well as the HV and 6 volt filaments but you also must add to the transformer extra voltage ac output to account for the voltage drop across the rectifier tube, tube manual states this, typical transformers used in the old arrl manuals show 325 to 350 volt either side of center tap transformers and high as 375 volts, this assumes the highest drop rectifier and a cap/choke, cap power supply. just a tube and caps i see no need to go above 300 to 325 at the very most with modern line voltages.
Late to this it would seem, at least parts have had time to restock. I’ve seen people apparently struggling to get parts, no idea why, I just phoned my electronic store and they ordered me a Hammond 369ax today (Brit)
Going to make the pine board tx’er into an old champagne box, tubes poking up through. Updates as parts arrive!
Hi Bob,
Like you, I am an old-timer and excited about building this rig. Anyone put it on 160 Mtrs? (My favorite band— which got
me into Ham radio). I plan to use large variable cap. on the pi output but may use a larger coil in the output…
don’t know. Is the AM freq. for 160Mtr comms 1.995 MHz? Like the simplicity of the rig and audio eq. (Like you, I am a
mike fan.) (I am a retired broadcast engineer.) Take care & 73. Steve Molna,r W8ANJ. stevenkmolnarw8@gmail.com.
he has it on 160 with the stock circuit but uses ALL of the 811 amplifier coil and the stock 365pf variable caps.
Hi Steve
Hope you have found the 160 better ‘upgrade’… it works SO well.
BOB HEIL
I just finished the PBP as an aluminum chassis model. With 200 volts it packs a punch with one-watt out. The audio, on the O-scope at least, is very clean. Now I just have to find someone to work!
73,
Dan – W7OIL
Vancouver, WA
What is with the light bulb shown in the video? Is that just in series with the antenna? Where is it in the schematic?
So when are readable drawings for the cw modification going to be posted?
I have viewed the video many times and can not make out the ratings for the components.
73,
Mike
N2CEC
So, i turned the transmitter on and immediately fried the 22kohm 1w resistor on pin 4 of the 6v6. This is the first component from the switch feeding 370 vdc.
Bad resistor?
I have bunches of tubes but NO 6aG7. Is there a direct replacement or easy mod to use something else in the xmitter?
6ag7’s can be got in lots or singles cheap on ebay. I paid no more than $4 for mine.
I don’t know where else to post this review but I bought the purple PR77DP for my ham station because it looked cool. I thought it sounded pretty good with my pine board. My 19 y/o son immediately grabbed it from me to use to stream his “fortnight” games on twitch.tv.
Wow. My oh my. He sounds great! By far he has the best audio on twitch.
Thank you for the coolest looking and the best sounding mic ever!!
KZ9S
I’m new to radio/electronics. What gauge wire should I use to connect the components?
Hi Bob,
A nice project. I’ve built many valve related things over the years. I don’t think I’d like to use that Chip Stick because as I understand it shorting out a capacitor doesn’t do it much good. On high voltage supplies I build I have a 1000k Ohm resistor wired permanently to earth on the end of the rectifier chain which discharges the chain voltage quite quickly to earth. Sure, it takes current when in use but it is negligible. Then after switching off always check with a voltmeter before touching anything. By this time certainly any lethal voltage should have been reduced to a safe level. In about four seconds it’s down from 295v to around 70 and still going down, but slower. At ten seconds it’s around 24v. Maybe then use the Chip Stick. I wait longer then use a screwdriver blade to short it to earth.
Bill, G4GHB.
Soon to be my winter project! I need to build my own version of the pine board project. I got into Ham Radio from building crystal radios, my wife’s cousin is responsible for my addiction ( he’s the one that said you really need to get your license. You know how to receive now it’s time to transmit) I’ve built a few x-tal sets with the intent of making them look like they came from the 30’s or there about. I’ve also built a CW transceiver with a crystal selector to change frequency on the 40 meter band using the Tuna can kits and modified them to my needs and built what I call my 40 Meter Field Radio, it runs on battery power all enclosed in a wood shoe box and a nice machine turned front panel. I’m pretty proud of it, it works! Now I just need to get proficient at that code(all in due time!)
Bob, I modified the preamp circuit to remove the bright switch arrangement and put a mirange control pot in its place with a few caps and resistors. then I built the transmitter minus the rf section and replaced the choke with an Output transformer and put a 6L6GB in the 6v6 socket, built the power supply same as yours. built it all on 1 board, I use a 3 to 1 transformer to couple my 1 and 2 tube regen sets to it and even my shortwave crystal radio set. works great as an amplifier. I built another one in a unique wood cabinet I made I used a dual section pot for each control from volume to bass to midrange to treble. now I have a stereo amplifer and I play my Herb Alpert Collection thru it from my reel to Reel deck. Lastly I completed my pineboard with an added 6L6GC stage and is modulated by a 6L6GC in place of the 6v6 I feed the 6ag7 stage and preamp with 200 volts and the final stage with 400 volts. I get much improved output the lower 6ag7 stage voltage lets me run the thinner crystals easier. also I put a midrange control on this pineboard as well. been sick for awhile, I feel better and want to get back to building my radios. thinking to sell alot of my geewhiz commercial gear and build more radios to use. Also I am working on a circuit to feed the rf from the 6ag7 into and output the ssb to a final like an 807 in place of the 6L6. Hope to key my original to your plans pineboard in cw mode with my commodre VIC 20 with a cw interface.
Would someone be able to model these circuits in EveryCircuit, QUCS, or some other similar electric circuit simulator? I’m trying to wrap my brain around how the electrons actually move around in these circuits. Although George does a great job talking you through the circuits, I’d still love to see these play in a simulator.
Bob, we have a facebook page if you want to contribute.
https://www.facebook.com/Pine-Board-transmitters-and-receivers-224703171789824/
Hi Bob, I have completed the Pine Board Project. This is the first time I made anything for AM or SSB. Enjoyed it very very much.
On CW the transmitter works very well at 4 watts. The power meter fluctuates as I key the transmitter.
For AM the meter stays at 4 watts even without the D104 mic connected. When I connect the mic and speak, the meters stays at 4 watts. Not sure if this is normal for AM.
I do get audio out and can hear myself on a powered speaker, I can also here myself on my ICOM 7610 and a Halli 120.
So I am not sure if I have a problem or not. Looked over wiring. All looks good. Any feedback will help.
Thanks and 73,
Mike N1CHP
I am genuinely delighted to glance at this website posts which consists of plenty of useful information, thanks for providing these kinds of data.
The preamp appears to use a 9-pin miniature tube socket with an octal flange. Where’d it come from? I didn’t see anything like that on the website of Antique Electronic Supply.
Not good in math. Can someone give me a helping hand here? On the parts list for the Microphone Pre-Amp there is a list of ceramic disc capacitors: 0.0047, 0.001, 0.01, 0.047 and 0.1. And also resistors 1k, 100k, 1M, 50k, and 10k.
Can someone help me here with the voltages when buying them, because they are listed in different voltages from the sellers. I don’t know which ones to buy for the Pine Board Project Microphone Pre-Amp.
Thanks and 73
Richard wb6rem
you can use mylar and polypropelene caps in the audio chain. ceramic and mica for the rf section. even the caps on the 6v6 part of the rf section if not electrolytic can be poly caps. RF YOU would use mica or disc ceramic.
Hi Bob,
It seems that AF4K, does not have the 3.885 MHz crystal nor the 7.290 MHz crystal any more. And have been trying to find them at other sites on the internet. Have not found any so far.
Richard, wb6rem
you can feed this with a small DDS VFO with a switch to change between crystal and VFO. I did this to mine.
I really like this project and would like to give Bob an attaboy! I think this would be even better if some one would offer all the parts in a ‘kit’. I would be willing to pay for that, as it would be a service to myself and others who are not as able to procure those parts. I can follow instructions and assemble radios and other items from ‘kits’. If this has already been done please say so and let me know where to sign up and order one.
James
N5ROJ
You can get the kits at Antique Radio Supply
http://www.tubesandmore.com
73,
Mike
Last nights show (6/12) Bob aired some builders concerns with hum. I used to build guitar amps and here are a few things to try. Bob’s comment to use both green filament wires is a good one. I also used to tie one green filament lead to the cathode pin of the output tube elevating the reference voltage and not allowing it to float. Also twisting the green leads tightly on the route to each tube and routing them away from any input stages really helps. Also make sure all grounds are tied to a single point on the board to eliminate loops. Always place power supplies at the opposite end from your input stages. Of course you could eliminate the heater hum totally by running the filaments on DC as well. Everybody builds differently so your mileage may vary.
I agree.
Removing the filament supply from ground usually increases hum and “buzz” due to primary to secondary transformer leakage.
Good way to significantly reduce hum is by using a transformer with a center tap and grounding the center tap.
Since the transformer in this transmitter does not have a center tap an “artificial center tap” can be created with a pair of 220ohm 1/4w resistors. Connect each green filament wire to ground with a resistor.
This reduces the magnitude of the voltage in each wire by half and by twisting the wires the EM fields cancel each other out.
Another thing is to make sure microphone housing, mic ground wire and all sockets are truly grounded. Since there is no metal chassis or panel this can be a problem.
KZ9S
Similar and more precise way to reduce hum in audio circuits is to put a 470 ohm potentiometer across the heater supply with the centre wiper to ground and adjust it for minimum hum. Of course it will probably be about in the centre of the track, but not always and this gives a very good hum null – usually.
Nick, this is the only comment about the Pine Board project that we see and it was approved.
Outstanding project, Bob! I’ve been Elmering my grandson and a couple of his friends toward their tickets, and they’ve
had a blast building their Pine Boards…..and learning quite a bit in the process! :>)
Just a quick question; why the 1N914 Si diode in the FSM? A Germanium like the old 1N34A, 1N65, or 1N67 would exhibit far greater sensitivity.
Have there been any changes to the design following feedback from the January 2018 ARRL article? It’s all gone fairly quiet and it’s being discussed on the AM Amateur Radio Europe fb group now.
I added two contributions here in recent days. One was to point out that the Pine Board Project was being discussed on the AM Amateur Radio Europe facebook page, and the other about hum from heaters in audio circuits. They were ‘awaiting moderation’, but have now disappeared.
Is this page now closed for new comments or is there a problem adding new posts? Either way could admin just drop me a brief email to the address I provided please? The AM Europe guys are interested in this. Some would like to follow the project and may have questions to post here.
Thanks.
Nick
Hi Nick, The comments were awaiting approval. It keeps spam out of the comments to have a person approve them all, but it also means if that person is out of the office it delays them getting approved.
Have my posts been checked for spam yet? There’s still some interest on the AM forum, but interest might be starting to fade if project updates take too long. Thanks.
Hi,
I recall Bob showing a single tube transmitter that he built in one of his videos, prior to the two tube version. Is there an available schematic for the single tube setup? Not the power supply nor the modulator, just the transmitter.
I’ve searched all the references to the word “choke” in the comments but did not see anything addressing this question: For the Pine Board PRE-AMP — some schematics and layouts show a 2.5mH choke at the input, some don’t. Same with the parts list. It’s not in the photo, so I’m guessing it was dropped from the design? Even so, I would like to know its original purpose since I have various uses for this pre-amp. I think I’ll be winding my own chokes, so any guidance on resonant frequencies (to shoot for, or avoid) would also be helpful. Thank you!
Keeps rf out of the mic. However a 100 pf capacitor across the mic input before the resistor will do pretty much the same. Look at the old 1950’s ARRL handbooks.
Bob- the power supply needs to have the switch AND the fuse in the same (hot) leg of the line to the transformer. Whichever is off or open could potentially (pun intended!) leave the hot side connected to the transformer. There’s some disagreement as to whether the switch or the fuse should go first- I put the fuse first in case there’s a problem with the switch itself and unplug the circuit when replacing the fuse. Others put the switch first so the fuse is cold and can be replaced without unplugging.
Scott Todd
N0BST
Where can I buy this as a kit so I dont have to get the parts separately?
Im intrested! I wanna build this!
This was a fun build.
Are there any plans for the future, with modules that could be connected to the power supply, like a code practice oscillator ?
Crystal Oscillator Problem:
I am having trouble with the oscillator section. I can tune the transmitter with great AM modulation and audio. But when I unkey and then key the transmitter section again there is no output and the crystal oscillator is dead. I can kickstart it again by adjusting the output tuning capacitor to minimum and then readjusting for maximum output. This happens on both 80 and 40 meters. I am using original FT-243 crystals that work fine with my AC-1 and other homebrew projects.
Any thoughts on where I should start tinkering?
73,
mike n0mopm
Would you have time to post an audio input circuit that uses the old-fashioned telephone carbon “button” mikes? I realize these are not high fidelity and have a limited audio bandwidth, but they have a higher output and would be fun to play with. I have a bunch of these and no place to use them!