Back in the 60's we used a lot of B&W coil stock, usually one inside another
to couple output to an antenna. Still the usual method or a tapped coil, for
AM broadcast uisng a tube transmitter. Solid state goes into a PI or PI-L
that is tapped. You tap down the coil to get the best output, one end to RF
output coupling cap the other to ground, or center grounded on push pull with
overlaying wrap. Used ferrite rod for QRP stuff. Can do the same today but
use ferrite core torroid or similar since coil stock is a little harder to
get. On some stuff the output coil was only a turn or two to get the hi-z to
low z transformation.
Henry AA9XW
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