[Amps] Minimum value of plate chokes

[Carl]

One of the fallacies of the past was to install a "VHF" choke after the
primary one. While it looks good on paper there is very little VHF
energy in a proper HF amp that will get past the primary choke and
bypass. That VHF choke could also possibly cause problems depending upon
its location and shape of the RF cage. A GDO will reveal resonances
caused by the cage dimensions.

In the SB-220 (and other amps that use it) I always remove the VHF
choke, RFC-2, and replace it with a wire wound glitch resistor which
does double duty as a very RF lossy choke. Then add a .0047 at the base
of the 50 uh plate choke.

When room is available, the 225 uh Ameritron choke can be used to
upgrade from lower values. It is also sold thru RF Parts.

Mouser carries .0047 and .01 Vishay/Sprague disc ceramics in 3 and 6kV.
They are cheap insurance.

Carl
KM1H