Bob wrote:
"There`s a 99 FM xmtr a couple of miles to the SE of me, lower in
elevation, right in the path of all the other stations - & right smack
in the middle of the FM band."

Bob seems to be lucky that the elevation of the interferring station is
enough lower that keeping the receiving antenna low hides it. That seems
to be what`s going on with the car radio and the built-in antenna on his
stationary radio.

Further suppression can come from a parallel-resonant trap in the middle
of his FM antenna element(s). This should make the elements an open
circuit at 99 MHz. Bob`s other stations aren`t on 99 MHz.

For higher Q in the parallel-resonant trap, it might be wise to use
1/4-wave short-circuit stubs. Impedance should be high for 99 Mhz and
lower for other frequencies. For a folded dipole, you might try to use
one, 1/4-wave short-circuit stub and locate it in the middle of the side
of the dipole opposite the feedpoint. This can all be made of 300-ohm TV
twinlead if desired. This may not be as effective as stubs in each side
of the 1/2-wave dipole. Folded dipoles are really loops. Frequently
loops have similar characteristics, open-circuit or short-circuit.
Placed in the middle of each side of the driven element of the folded
dipole, its resonance will be disturbed at the frequency of the 1/4-wave
short-circuit stubs.

Best regards, Richard Harrison, KB5WZI