[HBR] Using a BC-453 BFO

[Ian Wilson]

I dug out a BC-453 BFO coil (5852 I think) and a 6C4.
The following components were selected only by being close to hand:

  - plate to pin1 of the coil (no idea which is pin1, which pin3; I was
lucky)
  - grid through parallel 47k/0.001uF mica to pin2
  - B+ through 22k to pin3 (see above)
  - cathode to ground
  - solder tag connection to coil metal, grounded
  - 10pF from grid to frequency meter

This worked over supply voltages from 90v to 250v. The tuning range is
about 83kHz to 86.2kHz. You would want to follow Breck's modification
to disconnect the internal variable capacitor to get a bit more range,
probably.

Note that the original Command Set plate decoupling resistor is probably
too high (150k) to work with a 6C4 (which is electrically half a 12AU7 and
is a somewhat high plate-current triode).

Hope this helps.

73, ian K3IMW