I didn't see this post on the reflector when I previously sent it.
Sorry if it's a dup!
Some years ago, we installed a 155BA about 8 feet above a 3 el 40
(full size elements) at the W3GM contest station. We noted a
degradation in gain and pattern as well as a severe degradation in
VSWR which denotes excessive coupling between the two antennas. The
40 M beam seemed unaffected. We then removed the 155BA and tried a 4
el Cushcraft which also showed severe interaction. Again the 40 was
basically unaffected. We didn't try turning the 15 boom 90 degrees.
This might have worked but we didn't want to deal with the dual-dial
azimith calibration.
The 40-with-a-tribander configuration is well documented and appears
to work well in most cases. This is what I use at my station (TH6 &
40-2CD).
It might have been possible to adjust element lengths and spacings on
the 15 M antenna to restore the performance but we decided it wasn't
worth the effort and installed the 15 on it's own tower.
73, Stew K3ND...
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