[TowerTalk] Another way to make a CM choke ?

David Gilbert xdavid at cis-broadband.com
Thu Dec 14 19:24:12 EST 2017


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 at arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
>
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of David Gilbert
> Sent: Thursday, December 14, 2017 21:12
> To: towertalk at 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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