[Amps] TMC amp toroid tank

[k7fm]

Years ago I tore apart a small RCA AVT-112 (I am guessing at the numbers). 
It was an aircraft transmitter for WW-II Piper Cubs types using a 6V6 final 
on 3 MHz.  It had a wonderful inductor tuned by a large powdered iron or 
ferrite core.  The inductance was switchable.

I eventually decided it would be perfect for an all band antenna tuner.  The 
movable core allowed varying the inductance.  Worked great on 80 and 40 
meters.  However, on 20 meters, the output dropped down to almost nothing. 
I had almost no test equipment at the time, but finally determined it was 
the core that ate up all of my power above about 10 MHz.  Replaced switched 
coil with a conventional coil and things worked as expected.

I have never trusted those things since - without a lot of testing.

Colin  K7FM