[R-390] 6082's and regulators
David Wise
[email protected]
Fri, 3 Jan 2003 12:19:46 -0800
> From: Bob Camp [mailto:[email protected]]
>=20
> I guess the first question to ask is:
>=20
> Can you even measure a change in the supply voltage as you=20
> tune a signal and
> if so how much?
I'm sure you can. As signal strength varies, so does the
AGC and consequently the RF amp, mixer, and IF amp cathode
currents, which make up a respectable fraction of the
unregulated B+ load.
<Anecdote> While working on the 3DW7, I spent
many evenings listening to the beat note of an
SE-3 external BFO against my HP8640B crystal-locked
signal generator. As I ran the attenuator up and
down, the beat note changed by about a whole-note IIRC.
</Anecdote>
I'll report back with hard data.
This isn't the only source of frequency variance.
AGC on the mixers causes small changes in their
dynamic interelectrode capacitances, which reflect
back to their respective oscillators. I didn't
say these are large effects, just that they exist.
There's a fascinating section on this phenomenon
in the Radiotron Designers Handbook.
73,
Dave Wise