Thread: Franklin VFO ?
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Old 17th May 2019, 2:05 pm   #41
G6Tanuki's Avatar
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 7,891
Default Re: Franklin VFO ?

Point taken about there being a bit more thought behind the original enquiry than just 'building an oscillator to get the Squadcal on air' !

One thing I vaguely remember from the couple of hours of lectures about oscillators I underwent 40 years back (most of which was actually about generating ramps/staircases for video/radar stuff and multi-phase clocks for digital circuitry...) was that the noise-power contribution of an oscillator increases more-slowly than it's intended output as that output power is increased.

So - other things being equal - it could make sense to generate the oscillations at high level then attenuate them down to the required level, since the attenuation will also attenuate the noise component.

(The downside, of course, is that you've got greater power-dissipation so greater self-heating of the oscillator components which is a bad thing from the stability-perspective).

I've always pondered if this concept might have somehow been behind the design of the local-oscillator in the TCS receiver - which uses a 12A6 power beam-tetrode!
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