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Re: [TowerTalk] Another way to make a CM choke ?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Another way to make a CM choke ?
From: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 14 Dec 2017 17:24:12 -0700
List-post: <mailto:towertalk@contesting.com>

That's exactly the chart I remember seeing.  Thanks for resurrecting it!

Dave   AB7E


On 12/14/2017 2:48 PM, David Robbins wrote:
Ancient reference for aircore baluns:  
http://www.k1ttt.net/technote/airbalun.html


David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373



-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of David 
Gilbert
Sent: Thursday, December 14, 2017 21:12
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Another way to make a CM choke ?


I'm pretty sure some of the common mode choke approaches do exactly that ... 
except using the stray capacitance between the shields of the turns to get the 
resonance.  I suspect there are websites showing the right configurations 
(number and diameter of the turns) necessary for resonance.  It's been a while 
since I read Jim's paper, but I think he mentions that approach as well.

Dave   AB7E



On 12/14/2017 1:32 PM, Jim Thomson wrote:
Ok, for MONOband use only, what about a simple parallel resonant circuit, 
consisting of a solenoid coil of  50 ohm coax + parallel resonating fixed or 
variable cap, or padding a variable cap ?
With cap wired between input and output braid.  On paper, this appears to be a  
very high Z, and low Q device.  And wide enough to cover one ham band in 
question.   Is it doable ?
Whats the optimum  L to C ratio  for this concept to work ?   IE; we would want 
the highest Z practical, but a Q such that the high Z covers an entire band, or 
portion of one band, or freqs of interest.

Jim  VE7RF
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