Jim,
I don´t buy that.
When the CM noise is, as you explained, coming down the inner conductor how
could you measure any difference in CM current with a clamp on RF ammeter on
a tower leg or feeder when a CM choke is installed at the feed point of the
antenna?
I direct feed my 160m and 80m Dipoles and never had noise issues.
With my elevated GP on 160 I am direct feeding the radial and the shield is
connected to the tower at the 50 ohm point, no noise either. In opposite, it
is my best receiving antenna as well, better then the 100m long beverages.
Cabling is done as Stan assumed.
73
Peter, DJ7WW
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson
<Let's assume a coax going to an antenna is buried to the tower, the shield
is grounded with a short length at the base, the coax is inside the tower
and the shield is electrically bonded to the top of the tower and anything
else that would be considered good <practice for a good RF and lightning
ground.
<How is common mode noise making its way to the feed point and back to the
receiver if you have something less than multiple cores at the feed point of
the antenna?
<Stan, K5GO
### CM goes up the tower faces to the top of the tower, then to the
ant...then back down the center conductor.
## Easiest way to see if the CM choke is doing the job, or to compare no
choke, lousy choke, good choke,
is to use a clamp on RF ammeter, like the deluxe version that MFJ sells.
MFJ-854. Measure it at the base of the tower,
then in the shack.
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