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Re: [TowerTalk] Coax, conduit and toroids

To: Ian White GM3SEK <>
Subject: Re: [TowerTalk] Coax, conduit and toroids
From: Jim Lux <>
Date: Wed, 27 Jun 2012 05:47:02 -0700
List-post: <">>
Or if he has a connector at the base, then adding a choke is easy, either with 
slack in the coax, or a connector used inline version.

On Jun 27, 2012, at 1:50, Ian White GM3SEK <> wrote:

> K8RI wrote:
>>> 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 
>> your money.
> 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 
> in case".
> 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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