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Re: VTTC - audio modulation

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Herwig, All!

>IMO(!) modulation means superimposing two signals onto a
>nonlinear device. Linear(!) modulation is obtained only, if both
>signals are not clipped. Therefore the operating point of the tube
>should be placed between A- and B-mode. Please correct me, if
>I'm wrong.

Well, the only important distinction is the modulated class C
oscillator which you have already commented on anyhow.  Linear rf amps
for SSB service are always class B (or a close variant) - with any
luck, a class B oscillator should have an efficiency not far removed
from 60%+ at full output, so you won't lose a lot by using class B.

>>>Wouldn't modulation cause the oscillation to stop?
>> It all depends on the modulation depth
>- So overmodulation would cause the oscillations to stop and a low
>modulation depth means low loudness?

Basically yes, you've got it!  However, I recall those who have built
these things do not complain of low loudness despite the necessarily
low modulation depth, a couple of websites I've visited say it's
plenty loud enough, even with pipsqueak power to the TC.  "Low"
loudness is thus very much a relative term :-)

Geek#1113 (G-1)