[BC] Inductor Needed

[Craig Healy]

> > Like on the RCA BTR-1R1 in the output network?
>
> NO ! That's just a coil with a moveable slug in the BTA-1R.
> The thing in the 21E is a coil inside a coil; a transformer.
> Better yet would be a VARIOMETER,  like in the push-pull output of the
> RA-1000 and, I think, BTA-1L; a large coil with a small coil inside that
> rotates to vary coupling...........

The 1940 vintage RCA DX5 used that between the RF driver and final.
Balanced tunable coil outside and a small coil inside that can be turned to
change the amount of coupling.  I have one in my basement from one of those
rigs I removed from WPRO-630 around 1975.  Can take a picture of it if
anyone is curious.

Come to think of it, I also have a later one.  The outer is a plastic tube
around 6" diameter wound with what looks to be Litz wire.  Would tune to
below the broadcast band with a common 365pf cap.  Inside coil is maybe 10
or 15 turns on a rotatable plastic tube.  I'll have to dig it up to count
turns for sure.  Might be interested in selling it.  I have a smaller one I
made into a receive antenna tuner.  Works pretty well, though a ferrite
toroid seems to be better.

Craig Healy
Providence, RI