[ARC5] "Curing Chirp in Command Transmitters"

[AKLDGUY .]

> Whether or not the heaters run from AC or DC doesn't really matter.
> The tubes have indirectly heated cathodes which are independent of
> the heater voltage source.

In a general sense, true. But heater pin 7 of the Command set VFO is
connected to the cathode (pin 8) which is very much live with RF since
it is connected to a tap on the VFO coil.

Should we leave the circuit original and use DC for the heaters?

If we leave it original and simply use AC, does that cause an AC modulation
of the VFO amplitude or frequency?

My answer is that we can probably use AC, based on the assumption (yet to
be investigated) that the pin 2 winding is connected in opposite phase to
the
cathode-tap-to-ground winding, and therefore the AC appearing in both pin
leads cancels out. The cancelling is probably why the pin 2 winding is
there.

I don't want to open my VFO can to investigate. If someone out there has a
coil, please let us know whether the two windings are connected so as to
cancel. ie. the pin 7 end of winding B corresponds to the pin 2 end of
winding A.

Does anyone understand a word of this?

73 de Neil ZL1ANM