[TowerTalk] Placment of common mode chokes

[Bill Ogden]

I think I understand the value of a choke made from coax passing several
times through a 31 material core. My question is "where should these be
located?" in real situations.

My antenna configuration is probably quite typical.  A 55' tower with a
yagi on top. An inverted V a few feet below that. A "half sloper" attached
about 15' below the top.  This means three coax runs going up the tower. At
the bottom they go underground for about 40 feet to my basement. Operation
is 80 - 10 meters; maximum 750 watts.

My goal is to reduce unwanted noise to the receiver on all bands.  (I have
no apparent RF in the shack and that is not a concern.) Where should chokes
be placed? How many, in a practical sense?  (I am in a somewhat "far
suburbs" location. No specific noise sources, but the background noise
level on 80 meters is a concern. Maybe the noise level on the higher bands
is an unrecognized concern?)

I see the large 31 cores are $7 each from Mouser.  It appears that several
are needed for each choke. The cost is not unreasonable, but I do not want
to obtain more than I need.

Bill
W2WO