Owen Duffy wrote:
As you know, trapped antennas are sometimes explained by considering
the traps to be equivalent to frequency selective switches that are
o/c or s/c at certain frequencies of operation, and conveniently
disregarding the conductors on the outboard side of the o/c switches.

Traps are high-impedance devices at their resonant frequency.
For them to work properly, they need to see a low impedance on
the far side of the trap. If they see a high impedance on the
far side, they cease to be "traps" and become the phase shifting
coils described by Kraus useful in a phased array.
--
73, Cecil http://www.w5dxp.com