Determined Sleuth Solves Field Day Inter-Band Interference

By Bill Willcox-KF6JQO

During the last three or so ARRL Field Day events the phone stations have been plagued by interference between the 10 and 15M bands, and to a lesser extent the 20M band as well. 

The transceivers for all three bands were within 10-20 feet of each other and all three fed individual band pass filters by means of lengthy coaxial cables.  The band pass filters then fed a multiplexer that in turn fed a multi-band hex beam antenna by means of a single coaxial cable equipped with a choke at the antenna.  Note: the band pass filters and multiplexer were all mounted on the same aluminum base plate in a plastic box.

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