Topband: Horizontal Waller Flag
Richard (Rick) Karlquist
richard at karlquist.com
Fri Sep 11 11:43:50 EDT 2020
On 9/11/2020 8:06 AM, David Cole via Topband wrote:
> My next and final problem - when I have the tower retracted approx 25ft and the fiberglass stub mast I have good acceptable directivity - If I then raise the tower by 20 feet then the polar plot is and directivity disappears - lower the tower back down and the polar plot returns to normal.
> I did have a masthead preamp installed I removed this - no difference - I then put ferrites around the rotator cable and a common mode choke at the bottom of the tower thinking that the coax lead which was originally coiled on the floor with the mast down was now acting as a vertical antenna - none of these made any difference. my direct email is dave at g3rcq.com
> Thanks from Dave g3rcq
I ran into a problem like yours with tower raising. It turned
out that the feedline was acting as a vertical antenna and
the actual RX antenna did not have adequate feedline isolation.
When the tower is lowered, the unintentional vertical antenna
As far as ferrites around the cables, etc not working:
you didn't say what you used, but it was clearly inadequate.
Common mode choking in the BCB is quite difficult to pull off.
Sliding beads onto the rotator cable definitely won't work.
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