I am not sure how well a BN-86 acts as a choke but assuming that you
have quality coax and connectors, you may be just hearing noise that
the antenna is picking up, which is something that it is designed to
do. Lately it is difficult to avoid RFI from poorly designed
appliances and bad power pole connections. One easy way to check is to
listen to the noise while rotating your antenna, looking for signal
strengthen variation. If you are lucky the noise could be coming from
your own home.
John KK9A
Brian Rehmer KC4KK wrote
For sometime I have been struggling with noise (S4-7) on HF bands with
my TH-5DX tribander. I have ~125 feet of RG-8 routed to a BN-86 at
the antenna feed. There are several other feeds that are bundled
together for 40, 6, and 2 meters in the same run up the tower. The
cables route to the tower from my second floor radio room inside my
house. So, there are lots of things that can couple to the outside of
the feeds. I am considering adding common mode chokes to
reduce/eliminate the noise. Alot of the time the noise covers the
entire 15 M band. I can take a small loop and couple to the feeds at
base of tower and other spots along the feeds and see the noise and it
varies with position. It seem this points to common mode as culprit.
So, there are lots of things that can couple to the outside of the
feeds. I am considering adding common mode chokes to reduce/eliminate
the noise.
Question is should I add the choke prior to the BN-86 or replace the
BN 86. I expect I may need to add chokes to each of the other lines
too, but where. Should I add in the shack too or just exit from the
house to the tower. Ugh, it could need both - getting to be alot of
chokes.
Thanks,
Brian
KC4KK
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