The AM Forum

I've got lots of 1625 tubes. I'm wanting to build a 1625 transmitter. I've got the power supply. I think I probably have most of what I need in storage except mod transformer. I'm almost finished with a 1625 regen receiver and I'd like to start thinking of another project. I would build it in deprecate sections power supply, modulator, and rf amp. Anyone know of a good schematic for this? 807 or 1625 tubes? Thanks

Btw quad 1625's would be perfect. I'd really like to make this thing plate modulated. I'm mainly interested in 40 and 80. I don't have 160 so would like to be able get on the top band AM. I'm also wanting to really learn a lot with this so before I even build it I plan on really studying the circuit. I'd like to have the knowledge to be able to design a transmitter from scratch. Using old books I can make the calculations and design a basic amp circuit but when it comes to putting everything together I'd like I don't have the ability to do that yet. I've wanted to say this rig is homebrew for a long time, and I'd like to build it cheap but good with what I have.

Here is a good starting point.  1625's will sub for the Taylor T-21's easily.

From the "Radio Handbook" (Jones) #6, 1939.

73DG

How about a quad of 1625's class C parallel...modulated by a quad in Parallel  Push/Pull ? 

Copy the WRL Globe Chief 90 from the bama archives for the RF part.   It uses two 807's.

I love using those old tubes, like 6A6s and 42s, might even throw in a TZ-40 to spice things up!.  1625s are great, however, sometimes the sockets get a little hard to find. 

Vintage-style homebrewing is really a fun thing to do, but fewer and fewer folks are doing it these days.  It is much easier to fire-up the computer and turn on the Flex and forget about times gone by.  I enjoy it all....(although I don't have a Flex radio yet).  Lets see....does that rig have an 829B in the final?   :o ;D

I'm 28 and all I'm interested in is vintage equipment:) I found sockets on amazon.com. I have a few and they seem to be fine. Ill check out the recommendations and keep them coming. Ill check out the globe chief and I do want to run 1625s in the modulator as well. I've got a good amount of them, and they seem to be the cheapest tube in that power class.

Those sockets can't be that hard to get......are they?....

KL7OF that's the exact settup I was thinking of. I'm surprised I don't see that done more often. Seems like a good idea. I didn't know if there was some reason I was over looking other than the same power can be had with two tubes.

eBay has plenty of Chinese copies of the original 7L Johnson porcelain wafer socket, sometimes for as little as $2 per.

I bought a sackfull and the only difference I can see is the rivets are copper-colored rather than silver.

Drive them with 12A6's, a cheap & decent audio tetrode with the same 12-Volt filament.

73DG

A pair of 1625's modulated by a pair would produce a simple 100 to 150 Watt Class input transmitter. You could do a built in VFO and a buffer and a driver, a modulator and a power supply on one big chassis. A typical line up might be a 12SJ7 an old buzzard Hartley EC VFO patterned after the legendary stable BC-221 oscillator, 12A6 multiplier/Buffer, 12A6 Driver and then the pair of 1625's. The modulator could be a 12SJ7 mic amp, 12A6 triode Connected driver into the pair of 1625 Modulators. You might include a couple VR tubes for regulation and color.

You could do all that but of you just finished a 1625 regen then a screen modulated 1625 rig would be a piece of cake.
Normal audio transformer ,A twin triode for osc and modulator  and a carbon mic and battery and you are away. Oh I know it isnt is efficient as plate modulation. certainly is easier and cheaper though. OR, If you built a 1625 regen just nix the phones and regen pot and up the voltage and you have a good oscillator.(Keep the regen  build an osc specific unit. The speech amp/ modulator could be built from a 1625 as well since you are into them.)  No real difference in the circuits if it a conventional regen , A regen is just a osc down on power getting a boost from the antenna signal.  Circuit is pretty straight forward. Cut screen voltage in half and then push in some modulation to bring it back as close as possible at peaks. Homebrewing as previously stated is a blast. I find it so much fun I feel guilty doing it.
Don VE3LYX

I just really wang to do a plate modulated rig. I think I'll just do a pair modulated by a pair. Probably wouldn't be worth the extra trouble to do 4x4. I've got an apache already and 100watts seems to be fine. I've got a case I plan on using that's about the size of the apache. I will build in sections just to keep it simple and install all in the case when I'm done. The power supply I'm going to keep seperate because 1. I can use it for other projects. 2. I'm using oil filled capacitors so its very big with them in parrellell, maybe I should just get electrolytics. The vfo I plan on using an extra pto out of an r392 I have with switching capacitors for bands. I needed the transformer so I ended up with the extra pto. I also think this will be kept seperate for stability and also using on other projects. I do plan on keeping all tube except for diodes in the power supply. I do plan on building a low voltage qrp tube transmitter to go with the regen also. I'm doing this while doing a bunch of projects outside of the ham hobby so the transmitter might take a year to do but I want to do this. That is also why I want to build on seperate subchassis  to give a sense of accomplishment.

NR5P,

My favorite transmitter is a pair of 1625's driven by a 6AG7, similar to the "100 Watt Transmitter" in the older Understanding Amateur Radio book by the ARRL.  I added a 6AG7 buffer/multiplier, and modulate it with a pair of 807's running AB2.  The modulation transformer is from an ART-13, and the ratio isn't right for running AB1.  Getting this running was fun, and a little challenging getting the parasitics out of it.  Have fun.
Chris

The TCS mod transformers are plentiful, what is their ratings?

Carl

Never underestimate the feelings generated when you can say.."Rig here is homebrew, a quad of 1625's modulated by a quad of 1625's"....

20- 25 watts audio.......

Thats not what I meant, we all know it can handle a lot more than that as can the ART-13 version.

The TCS transformer is a 1:1 job so that would only be useful for a 2X1 topology (as done in the TCS). You need a 2:1 or 3:1 ratio modulation transformer like the ART-13 or Apache transformer to do a 2X2.

I guess it would also be a perfect use for an old tv transformer also.  I saw a writeup on using them on the amwindow website.

I guess I could leave it open enough to add a few tubes later on.  A tube window sure would look nice with eight tubes glowing through glass. 

I'll guess a kilowatt.  Let me know if I'm close.

Fred

.

Maybe a Sears kilowatt....like they rate their motor HP  ;D

My very favorite 1625 transmitter is a pair in parallel
grid-driven by a 1626 osc.  It even uses a 1629 and
xtal to check that the osc. is on freq.  
It's plate modulated by push-pull 1625s driven
by a 12J5 microphone amp.  (snicker....)   ;D

Sounds vaguely familiar!  ;D