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Author Topic: Suggestions for tubes/phone transmitter fab plz?  (Read 285 times)
KC9KEP
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Posts: 208


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« on: April 08, 2009, 11:08:34 AM »

Hello Elmers!

I'm finishing up the construction of my first HBR-11 receiver (QST April/May 1963 Ted Cosby).

It's the best functioning receiver that I've ever built! :-)

What I'd like to do is team it up w/a homebrew vacuum tube transmitter that can handle voice/phone mode of transmission.

Of course, most hams are probably using SSB or VHF FM, etc.

Can anyone make a suggestion on what sort of homebrew tube transmitter I could build in order to compliment my HBR-11 and so some QSO-ing?

(I already have built two CW transmitters, but would like to try phone.)

Did you have a "favorite" type of transmitter technology if you had used vacuum tube transmitters in the past?

I'm not too interested in DX-ing at this point .. just getting myself on the air with a homebrew phone compatible communications mode.

I usually receive a pleasantly polarized response from this forum, so I'm anxious to see what everyone thinks!

Thanks again & 73's

--KC9KEP

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WA3SKN
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Posts: 5558




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« Reply #1 on: April 08, 2009, 11:21:20 AM »

How "fancy" do you want to get?
I would start with a simple AM transmitter, either 80 or 40 meters... maybe even crystal controlled. (The tube VFOs drifted a lot!)  Oscillator, buffer, 6146 PA stage and probably a audio preamp and 6L6 audio amp to modulate it.
I don't have any plans, though.
Good luck with the project!

-Mike.
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WB6BYU
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Posts: 13576




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« Reply #2 on: April 08, 2009, 11:24:24 AM »

You could start by building a cathode modulator to plug
into the key jack of one of your existing CW transmitters.
(Presuming the key is in the cathode lead, of course.)

Beyond that it will depend to a large extent on the parts
you have available.  Plate modulated AM is great if you
can get a suitable transformer, otherwise you may need
to look at something like screen modulation (presuming
you want to operate AM, which is the simplest mode to build.)

SSB is much more complex, especially if you are going to
use GloFETs in all stages rather than solid state. But it
can be done, probably with about the same complexity as
the receiver you just built.  An intermediate approach
might be DSB which uses a balanced modulator but doesn't
need a fixed-frequency filter.  Of course, the early
SSB transmitters used phasing rather than filtering to
generate the SSB signal, and with some of the recent
work on cascaded phase shift networks this may be easier
to do than the old rigs with the B&W 2Q4 phasing network.

When looking at circuits I'd strongly suggest designing
it to use a real RF output tube like the 6146 (or 2E26
for lower power.)
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