[Amps] TMC amp toroid tank

[Gary Schafer]

I have an old TMC (LPA-1k) amplifier that I am getting going. It has a
toroid tank coil for all bands 1.6 MHz to 18 MHz. It has a pair of 3-500Z in
it with 3000 volts at 700 mills. On 160 the efficiency runs around 60%. 80
meters is a little less and 40 meters is a little under 50% and 20 meters is
less than 40%.

 

It is speced as 1KW output. On 20 meters I get 750 watts out at around 2K
input.

 

Anyone have any experience with toroid tank coils? Is efficiency normally
poor on the higher bands?

 

This thing has auto preset channels that can be programmed anywhere in the
1.6 to 18 MHz range. Motor driven band switch and tuning caps. Works real
nice but low efficiency. Maybe I need to add a conventional tank coil for
the higher bands?

 

Thanks for any help.

 

Gary  K4FMX