[ARC5] "Curing Chirp in Command Transmitters"

[Mike Morrow]

> In regards to the cathode and filament circuit in the VFO of the ARC-5
> tube.  It would appear that the circuit was originally designed for a
> directly heated cathode tube and they decided to go with the 1626 instead
> but not changing the initial design.

No...it's the EXACT OPPOSITE of that.

The 1626 MO tube being INDIRECTLY heated is THE ONLY reason behind this MO
design that uses tapped MO coil T-53A and T-53B together as a bifilar RF
choke.  This circuit puts the cathode and both sides of the heater at the
same RF potential, and thus completely eliminates the effects of heater-to-
cathode capacitance upon MO operation. 

Mike / KK5F