Topband: Question on common mode chokes

[Charles Cu nningham]

I agree.  We really  don't want the coax shield to be part of the antenna,
regardless of whether the antenna is vertical or horizontal. If the coax
shield is part of the antenna, it can seriously distort  the resonance and
the driving point impedance - hence the need for some common-mode isolation.

Regards,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Robert
Harmon
Sent: Wednesday, June 03, 2015 4:21 PM
To: Top Band Contesting
Subject: Re: Topband: Question on common mode chokes

Jim,

It will be interesting to see what others say but my take on this is that
the tuner function is to provide an impedance match to the vertical and
doesnt provide any choking.  You still should have the choke.

73,
Bob
K6UJ



> On Jun 3, 2015, at 9:42 AM, James Rodenkirch <rodenkirch_llc at msn.com>
wrote:
> 
> I seem to recall, while reading up on common mode chokes, where I wouldn't
need one if I employ an autotuner at the base of the antenna...is that
true/factual?
> 
> I have an LDG Z11ProII autotuner right at the base of my vertical - I did
add a common choke at the input to the autotuner (21' of my LMR-400 coax
wound around a piece of 4.5" PVC for the low bands) but wonder if that is
really necessary.  
> 
> 72, Jim Rodenkirch K9JWV
> 
> 		 	   		  
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