[AMPS] Chokes

[Phil Clements]

> My guess is that a gap would work if it was about 10-inches.  Mounting
> chokes at right angles seems to work better and save space.  A switched
> vacuum relay to short the larger choke as needed would undoubtedly work
> best.    This is how commercial. general-coverage amplifiers deal with
> hv-rfc resonances.   .

This works great, but expensive and chassis-consuming. Henry and Creative
Electronics deal with this on their 3CX3000A7 amps with open-frame relays to
short out the larger choke below 40 meters. Creative was very "creative" in
that they use a relay to ground two parallel 4700 pf 10 kv caps. The other side
of the paralleled caps connects to the terminal where the two chokes are
connected together. This isolates DC from the relay contacts so a smaller,
less expensive relay can be used here. The 9400 pf to ground prevents
resonance problems in either choke when it is powered on @ 40 meters
and up.

You are correct about Alpha et al using vacuum relay switched chokes in
their designs. They had no choice due to space constraints to do anything
else.

If you have the room, the RF Parts/Ameritron choke works quite well by
itself, and it is cheap.

(((73)))
Phil, K5PC




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