As a cash-strapped kid in the 1970s UK, I remember those Brown & Kneitel books occasionally appearing in our local public library and I would swoop on them whenever they appeared. For many circuits, the authors would say "...can be readily constructed using items from your junk box..." and I would think "I've GOT to get one of those junk boxes!" After 50 years of intense effort I now have such a junk box (I call it "home") and may even be able to tackle this project! 😂
I remember an American book in the library with articles such as "A one tube novice transmitter for 40 and 80 meters". This rig was my first. Later I built a two valve multiplier and 807 PA rig I used on 10 15 20metres as well as freebanding on 27MHz
Back when these books came out, it was expected that the builder had an awareness of high voltage circuits after all we got our parts from old TV sets and tube type radios and the term "easy" was relative to that time. Many builders had a radio and TV shop in town where we could buy parts and beg for to look through their trash and sometimes get advice from the owner of those shops. I like that you give warnings about high voltages and that you come up with these projects. Thanks for the great video!
I always love your project videos, Mike. Thanks so much for the inspiration and good advice. I don't know if I'll try this one or not, but it sure looks interesting and fun. Great video, as always! -K5SFC
16:09 - Stancor PS-8416. I looked over and I have one sitting on my desk! I use that and the Hammond 261C6 for many of my projects. I see you covered the Hammond as well. :)
Regarding the voltage doubler circuit: If you assume first that the 700V transformer doubler output is floating with respect to ground and the 42K resistor followed by the 4.7K resistor are a voltage divider - of sorts. so ... tying one end (0) of the floating transformer output to the 4.7K resistor and knowing that the current flowing into and leaving that node tied to ground is zero then "poof" magically you get a negative voltage across the 4.7K resistor. I often find that the way things are drawn can make it harder to understand what's going on.
When I see a voltage doubler, I still always have to scratch my head a little working it out. Seems like magic that you can double (or more) voltages without a transformer. Of course, it's not magic, as the voltage goes up, the current must come down.
@@Steve-GM0HUU Yep. If you just remember that you can build a voltage multiplier with just capacitors and mechanical switches then half the battle is won.
When I was a kid, around 1971 or so a friend of mine of my age who was a novice ham made from plans found somewhere an xtal controlled CW tx on an aluminum bud box which only used parts from a junked TV. Probably on 40 meters, but I'm not sure. He tuned it up using an incandescent light bulb. Any idea what plans he might have been using? They must have been in QST or some other ham mag.
I'd like to suggest a challenge. I've been looking for a while for a single-tube *transceiver* -- just *one* pentode (tetrode, even triode, but I doubt I'll find that) that switches back and forth between receiving (as a regen, I expect) and transmitting (either CW or suppressor modulation AM like this transmitter). I've got some miniature pentodes around, but I've also got spare 6146 tubes I bought for my (still not fixed) Heathkit SB-102 -- one of those, running around 300 V on the plate, might get me close to 10W output (though power supply transformers I can find/afford might limit that). I'd like to avoid being rock-bound, but I'll use a crystal if that's what it takes to tame chirp and drift. Seen anything like that?
It can be done, but the switching is the difficult part, whether relay or multipole rotary switch. Extra points - make the REGEN Crystal Controlled using the same rock so it puts you exactly on the same frequency.
A NEW HIGH VOLTAGE TRANSFORMER??!??! Who knew. Well there goes my retirement stash. At least I will be able to use my Heathkit GDO to set the tanks. You have a 10/6 regen video?? Fun side note, I built a 6 meter filter 30 years ago with that gdo and was unable to use it because I moved house. "Found" it last year and stuck it on my VNA and it was almost spot on for all of six. The last TOKO transformer was't quite right. Knew at the time but it resonated like the rest.
Thank the Audio guys. There are more high voltage tube type transformers out there than at any time since 1970. They are back! These transformers were 6 to 8 bucks in 1970 dollars. Still expensive today.
I'm wondering if they can run the tube at 700v just because the suppressor grid is at -70v? I.e. the suppressor grid might act as an ion trap. Still, 15mA at 700v is 10W plate dissipation, way above the rating.
For CW, it simplifies all right because you do not need the negative supply or modulation components. Just ground the suppressor grid. Keying a TRITET in the Cathode is a bit more difficult that keying a traditional Colpitts style Electron Coupled type tripling to 10M. The TRITET allowed good drive on harmonics, so it was popular for an 80M rock to be used on 40M, 20M and maybe 10M! too. But it may chirp on 10M.
Use Back to Back 12V CT Filament Transformers, able to select 6 or 12V voltage for the filament from the middle and double the output (120V) of the second transformer. Might have better luck finding filament transformers.
That is a good strategy and I have some examples on some videos of this. The surprise is that you need a bit more transformer than you think when you do this, and not al types convert back up gracefully.
Not one word about a spectrum analyzer. Harmonic regulations are much stricter now days than they were back in the 1970's. That "transmitter" is going to be far from meeting FCC requirements on harmonic output. I guess the most common attitude is, "who gives a shit!"
As a cash-strapped kid in the 1970s UK, I remember those Brown & Kneitel books occasionally appearing in our local public library and I would swoop on them whenever they appeared. For many circuits, the authors would say "...can be readily constructed using items from your junk box..." and I would think "I've GOT to get one of those junk boxes!" After 50 years of intense effort I now have such a junk box (I call it "home") and may even be able to tackle this project! 😂
Oh I get this! My first trip to a "city" and a real bookstore, I found used copies of many radio hobby magazines and books that were life events.
I remember an American book in the library with articles such as "A one tube novice transmitter for 40 and 80 meters". This rig was my first. Later I built a two valve multiplier and 807 PA rig I used on 10 15 20metres as well as freebanding on 27MHz
Back when these books came out, it was expected that the builder had an awareness of high voltage circuits after all we got our parts from old TV sets and tube type radios and the term "easy" was relative to that time. Many builders had a radio and TV shop in town where we could buy parts and beg for to look through their trash and sometimes get advice from the owner of those shops. I like that you give warnings about high voltages and that you come up with these projects. Thanks for the great video!
Hello Microwave1. Always happy to see you and your friendly and very interesting videos. Thank you .
I always love your project videos, Mike. Thanks so much for the inspiration and good advice. I don't know if I'll try this one or not, but it sure looks interesting and fun. Great video, as always!
-K5SFC
16:09 - Stancor PS-8416. I looked over and I have one sitting on my desk! I use that and the Hammond 261C6 for many of my projects.
I see you covered the Hammond as well. :)
What fun!! 😁 Thank you for the heads up on this circuit! I wish I could clone myself and build one up right now to try it out.
Regarding the voltage doubler circuit: If you assume first that the 700V transformer doubler output is floating with respect to ground and the 42K resistor followed by the 4.7K resistor are a voltage divider - of sorts. so ... tying one end (0) of the floating transformer output to the 4.7K resistor and knowing that the current flowing into and leaving that node tied to ground is zero then "poof" magically you get a negative voltage across the 4.7K resistor. I often find that the way things are drawn can make it harder to understand what's going on.
Without redrawing that circuit, I was scratching my head.
When I see a voltage doubler, I still always have to scratch my head a little working it out. Seems like magic that you can double (or more) voltages without a transformer. Of course, it's not magic, as the voltage goes up, the current must come down.
@@Steve-GM0HUU Yep. If you just remember that you can build a voltage multiplier with just capacitors and mechanical switches then half the battle is won.
Brilliant video, very interesting.
When I was a kid, around 1971 or so a friend of mine of my age who was a novice ham made from plans found somewhere an xtal controlled CW tx on an aluminum bud box which only used parts from a junked TV. Probably on 40 meters, but I'm not sure. He tuned it up using an incandescent light bulb. Any idea what plans he might have been using? They must have been in QST or some other ham mag.
This very likely was a cousin of the famous Novice Oscillator project that I cover in a another video series. Check it out!
I'd like to suggest a challenge. I've been looking for a while for a single-tube *transceiver* -- just *one* pentode (tetrode, even triode, but I doubt I'll find that) that switches back and forth between receiving (as a regen, I expect) and transmitting (either CW or suppressor modulation AM like this transmitter). I've got some miniature pentodes around, but I've also got spare 6146 tubes I bought for my (still not fixed) Heathkit SB-102 -- one of those, running around 300 V on the plate, might get me close to 10W output (though power supply transformers I can find/afford might limit that). I'd like to avoid being rock-bound, but I'll use a crystal if that's what it takes to tame chirp and drift.
Seen anything like that?
It can be done, but the switching is the difficult part, whether relay or multipole rotary switch. Extra points - make the REGEN Crystal Controlled using the same rock so it puts you exactly on the same frequency.
@@MIKROWAVE1 or find a way to build in an optional CW offset?
The GU50 is a pentode wich can handle up to 1 kV. Could it work in this case?
A NEW HIGH VOLTAGE TRANSFORMER??!??! Who knew. Well there goes my retirement stash. At least I will be able to use my Heathkit GDO to set the tanks. You have a 10/6 regen video??
Fun side note, I built a 6 meter filter 30 years ago with that gdo and was unable to use it because I moved house. "Found" it last year and stuck it on my VNA and it was almost spot on for all of six. The last TOKO transformer was't quite right. Knew at the time but it resonated like the rest.
Thank the Audio guys. There are more high voltage tube type transformers out there than at any time since 1970. They are back! These transformers were 6 to 8 bucks in 1970 dollars. Still expensive today.
Max plate voltage on the 6BH6 plate is 300, not 700. You could cook steaks on it.
I'm wondering if they can run the tube at 700v just because the suppressor grid is at -70v? I.e. the suppressor grid might act as an ion trap. Still, 15mA at 700v is 10W plate dissipation, way above the rating.
Well it may well help some. But honestly, they were lucky it did not arc over. You have to love these old bottles!
Great companion for my 50c5 xmitter TKS ok De kv4li
50C5! Nice
We demand white-hot glowing plates and sagging glass-envelopes! 🤣😂🤣
To operate on CW, would grounding pin #7 work?
For CW, it simplifies all right because you do not need the negative supply or modulation components. Just ground the suppressor grid. Keying a TRITET in the Cathode is a bit more difficult that keying a traditional Colpitts style Electron Coupled type tripling to 10M. The TRITET allowed good drive on harmonics, so it was popular for an 80M rock to be used on 40M, 20M and maybe 10M! too. But it may chirp on 10M.
73 from UT5RQ !
Will this work with an EL84?
Great choice
Bravo i zdravo profesore.yu1qg 73
No Uncle Henry and 11 m Side Band
I have Ameco AC-1 with Modulation
Good video !!! UA9CMR
Thanks for watching.
Use Back to Back 12V CT Filament Transformers, able to select 6 or 12V voltage for the filament from the middle and double the output (120V) of the second transformer. Might have better luck finding filament transformers.
That is a good strategy and I have some examples on some videos of this. The surprise is that you need a bit more transformer than you think when you do this, and not al types convert back up gracefully.
As always, Mike very interesting and much appreciated. 10m DX Machine 😂.
Not one word about a spectrum analyzer. Harmonic regulations are much stricter now days than they were back in the 1970's. That "transmitter" is going to be far from meeting FCC requirements on harmonic output. I guess the most common attitude is, "who gives a shit!"
What about building a safer version by using a 40673 driving a VN66AF power VMOS device and 12V at 5A just make sure you have no short circuits.
And it probably would have more output power. But you would have to come up with a modulator.
Have you been able to find a 40673 lately. Ya got an old GE TPL to look through? :)
@@radioguy19510 Ha Nope. I got a couple by accident in a hoard of transistors last year.
Really interesting and I shall follow the series but am not brave or experienced enough to try this one.
Suppressor grids were outlawed in 1978 violating the rights of electrons to be free.
Burt are you a free radical? Looking forward to Nearfester Fall Edition.
@@MIKROWAVE1 I doubt I will do another Nearfest video. They didn't bother to post the last one.
700volts! yummy!
You lost me at "I'm not going to judge".
80-40 500 watt amp would be cool to see. glass or transistor. transistor be safer thats for sure hahhaha
In the same book they have 3 Amplifiers, the largest a one tube Kilowatt Final with no more care or detail than the 1Watt we are playing with!
@@MIKROWAVE1 iam not that secure with that much voltage lol ..
Thanks a lot for a interesting channel!
A lot of useful information and ideas for a homebrewer!
73 de OH8UBJ/Juha