"Edmund H. Ramm" wrote in message
...

Several of the transmitters I named also used TV sweep tubes.
[...]

Yes, all several two of them: Eico-723 and Heathkit DX-20, apart
from the Drake 2-NT already pointed out by me. Which means they don't
belong in a discussion about true transmitting valves (807 and 6146),
and their respective merits regarding neutralisation.

BTW, the above mentioned Eico-730 is a modulator.

73, Eddi ._._.


I think I am detecting a hint of sour grapes here, Eddi. My post was a
reply to Ken Scharf's post saying the 6146 would be more stable than the
807 because of its higher perveance and lower lead inductance. The TV
sweep tubes generally have considerably higher perveance than the 6146.
As for lead inductance, some TV sweep tubes had exceptionally long leads
to reduce "blivets" (a.k.a. snivets, VHF parasitics sometimes associated
with Barkhausen oscillation); these were unsuitable for use in
transmitters above 7 MHz or so. One lot of 6HF5's ran the cathode lead
from the top of the tube to the base; these barely worked on HF [Bill Orr
W6SAI, "Full Blast" Operation of TV Sweep Tubes, Ham Radio, April 1968].

Yes, the Eico 730 was a typographical error. It should have been Eico
720. The DX-20 used a 6DQ6A which has only slightly more
transconductance than the 6146. The Knight T-60 also used a 6DQ6. The
AF67 used a 6146 with no neutralization. (Another rig I did not mention
was the Eico 753 which used a pair of 6DQ6's _without_ neutralization but
in AB1 linear mode. Of course, in AB1 it could not frequency multiply in
the final.) The 6146 has only a slight increase in gain over the 807.

As to whether receiving and TV sweep tubes should be included in the
discussion, 6L6 tubes have been used by hams in transmitters since the
1930's. In fact, the 1614 was a 6L6 designed for RF service. RCA even
notes that curves for the 807 apply to the 1614 within its maximum
ratings.

The original poster, Radio Vintage, wanted a simple 2 or 3 tube 80/40
meter transmitter with VFO. For circuit ideas, I believe that the large
number of articles using TV sweep tubes should not be ignored. The
discussion was not specifically about neutralization. I suggested
doubling in the final as a means to simplify the design in that
neutralization would likely be unnecessary.

73, Barry WA4VZQ