Richard wrote:
"Anyone know of any antenna system that would produce a real good null
in the FM band?"

Direction finding relies on sharp nulls. The small loop works well with
vertically polarized ground waves, but small loops don`t work well in
nulling out horizintally polarized waves simultaneously with a null in
vertically polarized waves .

The lack of a simultaneous small loop null in both polarizations was the
cause for development of an improved Radio Direction Finding (RDF)
antenna, which was patented by F. Adcock in 1919. The story is found in
the 19th edition of the ARRL Antenna Book on page 14-5.

FM broadcasts typically contain both polarizations, so what`s needed is
an antenna which nulls out both polarizations.

The Adcock antenna has been found to prooduce good nulls under sky-wave
conditions (containing both polarizations) at HF when loops produced
poor nulls.

Instructions and directional patterns for the Adcock appear in the ARRL
book. All that`s necessary is to approximately scale the Adcock for the
frequency of the null.

With the interfering station in the null, the desired station may
capture the FM detector.

Best regards, Richard Harrison, KB5WZI