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
goes away.
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.
Rick N6RK
My Technical knowledge is limited but, I have built directional AMBCB
antennas. Feed line isolation is critical to make a directional antenna,
directional! I have been criticized and been told, coax cable does not
pick up signal. Must be I don't use the right coax.
This from a previous post I made after I ran out and tested a 230ft Coax
and a 230ft 18ga twisted speaker wire, to see what BCB stations they
received.
"I found I received 13 stations with up to 5.5 S units on the
properly terminated coax. I tried many things to reduce signal pickup,
chokes, transformers, grounds, several chokes and transformers, but
could never get it to be quiet. So after reading some info about phased
antennas using speaker wire, I ran a twisted speaker wire out to where
my antenna was to start.
After terminating that, I found I only received 4 stations, 3 were
audible but at zero on my S meter and one that was almost 1 S unit.
Do I think the speaker wire has more loss than the coax probably, but, I
seem to have plenty of signal and it doesn't have much
signal ingress compared to the coax."
I have since went to Cat5 cable for my receive antenna. I started in
my haste just connecting Cat5 to my radio, terrible idea, but I learned
from it.
I tried several things to quiet the Cat5 and came up with something
that works very well for quieting the Cat5 in_MY_ situation.
I have the 235ft of Cat5 connected to a 260ft (property limited) BOG
that I use mostly for the AMBCB. The BOG points N/S, it seems to have
attenuated side lobes but not much front to back.
After reading a Laird Cat5 common mode article, I used their info to
help me build my signal ingress reduction box. If you're interested in
seeing what
worked for me, click here.
https://www.dropbox.com/s/e1lq7fxv0kggi5d/bog%20final%20design%20may%2030%202020%20common%20mode%20attenuator.jpg?dl=0
KF4ITA Mike Knowlton
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