[TowerTalk] Common-mode choke

[Jim Lux]

On 5/19/14, 9:07 AM, Steve Hunt wrote:
> That's right - to get meaningful results you need to understand the
> stray capacitance added by the test structure.
>
> Steve G3TXQ
>
>
> On 19/05/2014 15:08, Jim Brown wrote:
>> I don't trust any impedance measurements of chokes wound on #61,
>> including my own, simply because the Q is so high. Even the slightest
>> stray capacitance moves the resonance, and it's the resonance that we
>> need.
>
> ___


Beyond that, if the thing is so sensitive to surrounding structures, how 
close is your measurement fixture to where it will actually be used? 
You might optimize performance for your fixture, and it's worse in the 
real installation.

I think the take home thing here is that when it's a "choke" you're 
looking for, then you want fairly broadband and lossy.  If it's a "notch 
filter" you want, then resonance is fine.  I would guess that most 
antenna applications are more the "broadband choke" than the "narrowband 
notch".