[TowerTalk] Coax, conduit and toroids
Ian White GM3SEK
gm3sek at ifwtech.co.uk
Wed Jun 27 01:50:55 PDT 2012
>> Is it a good idea to create a coil of coax in or near the base of the tower,
>> run through ferrite toroids? I do this at the base of my vertical, but I'm
>> not sure if it's as useful for a horizontal antenna.
>I have a one of these current chokes/baluns on each of my sloping
>dipoles. On 75 I still had so much feedback that all the LEDs in the
>shack would light by the time I reached a KW out let alone 1.5 KW. I
>added a second choke in the 75 meter feed line at the tower and it
>cleaned it up to where I can not detect any common mode voltage making
>it back to the shack. If you need one, use one, if you don't then save
The problem may be that he needs to decide right now, while he is
installing the coax.
On the other hand, large ferrite cores will be very expensive imports in
ZL, so it won't be cost-effective to scatter lots of them around "just
One option might be to look up K9YC's recipes for ferrite chokes using
the big #31 clamp-on beads, and make the air-cored coil at the base of
the tower when installing the coax. Very little is lost by doing that
much in advance.
Later, if a "serious" common-mode choke does turn out to be necessary at
the base of the tower, then simply snap the big bead onto the coil that
is already there.
73 from Ian GM3SEK
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