Homebrew TX

[KI4YAN]

Looks like I'll be using the cheaper cousin of the 807, the 6BG6GA. I have a pair of them, so I'll need 60-70W of AF to fully modulate them, with overhead. Ouch, that's by far the beefiest AF amp I'll have done, the most powerful so far has been 25W.

Probably gonna use 6BG6's driving 6BG6's, with a 6AG7 40M crystal osc/VXO, with loop feedback from the RF stage to the AF stage: attenuate and sample the output, demodulate the AM, apply AF as negative feedback.

[w3jn]

I fully support this idea!  Use up some of them thar "junk" tubes and put 'em to good use.  There's little demand for 6BG6s anymore.

[KI4YAN]

This may be put off for a while, as I have a car to rebuild, and a N2 laser that has bit me again (I homebrew lots of stuff, especially lasers and electronics.) The car is a '72 Datsun 240Z, my newest toy

[KI4YAN]

After spending some time in the Tube Shack (my junk room) I've found a pair of NOS 6DQ5. Now, I seem to recall that a single 6DQ5 can make about 75W class C, and plate modulated that'd mean I would need about 40W of AF drive. I've got a 25W class A audio amp based on 6BQ6GTB's that if converted to class AB1, could probably make around 40W. I think that this transmitter appeared in the 1941-1945 editions of the Handbook, (I think I've figured out that ARRL is a bad word around here...) If anyone cares to look at it.

[Steve - WB3HUZ]

That's the same tube line up used by the Gonset G-76 and it worked pretty well. I think the 6DQ6's were triode connected in the G-76.

[w3jn]

, (I think I've figured out that ARRL is a bad word around here...)

There's really no such thing as a "bad word" around here insofar as organizations are concerned.  Everyone has their opinions, of course, and that's what makes for lively and interesting discourse here.   But nobody's gonna sock ya in the jaw for using one one of the best electronics bibles around 

[The Slab Bacon]

That's the same tube line up used by the Gonset G-76 and it worked pretty well. I think the 6DQ6's were triode connected in the G-76.

I love the little G-76s they're really kool rigs! Your close, Steve. The G-76 uses a 6DQ5 modded by a pair of 6DQ6s in a rather odd class B configuration. The control grids are tied directly to ground, and the audio drive is fed to the screen grids with no biass. It makes plenty of audio, but is kinda wierd lookin on paper.

                                                                          The Slab Bacon

[Steve - WB3HUZ]

Yes, as I said, "I think the 6DQ6's were triode connected in the G-76."

Of course, I can't read since, Jacob was considering 6BQ5's, a completely different animal, but very nice tubes. Personally, I'd go with the 6DQ6s, since they would produce more audio.

That's the same tube line up used by the Gonset G-76 and it worked pretty well. I think the 6DQ6's were triode connected in the G-76.

I love the little G-76s they're really kool rigs! Your close, Steve. The G-76 uses a 6DQ5 modded by a pair of 6DQ6s in a rather odd class B configuration. The control grids are tied directly to ground, and the audio drive is fed to the screen grids with no biass. It makes plenty of audio, but is kinda wierd lookin on paper.

                                                                          The Slab Bacon

[Steve - WB3HUZ]

Just happened to run across this info in the February 1980 edition of QST.

I would guess that for plate modulated service you could run about 2/3 to 3/4 the power/plate current.

[KI4YAN]

Ah, thanks Steve! 6JE6 is simply a duodecar version of 6DQ5, IIRC, and NJ7P seems to support that. Now I have a set of usable operating parameters, and albeit for a single tube, I bet that if I parallel two 6DQ5 I can get about 15/8ths the output current of a single tube, and probably about double the power. makes for a heavy mod transformer, but I've got some chunk iron here to rewind, so it's not a *huge* deal.

On the first attempt, I'm shooting for 70W carrier, then as I get some experience, I'll add another final and adjust the modulator accordingly, and go for 140-150W carrier. This being my first real transmitter, I'm worried about tuning up and finding no one around on 7.200Mhz. (my only crystal that falls in the 40m band...I've got a 3.686Mhz that I could double to get 7.372, but that puts me out of band, something I shouldn't do )

I guess I should go ahead and rebuild this 40M receiver into a proper cabinet first, though. If ya can't hear 'em, how ya gonna work 'em? I think the old saying goes...