Topband: Mother of all ferrite common-mode coaxial chokes

[Jim Brown]

On 7/13/2012 6:21 PM, ZR wrote:
> ----- Original Message -----
> From: "Jim Brown" <jim at audiosystemsgroup.com>
> Cc: <topband at contesting.com>
> Sent: Friday, July 13, 2012 4:37 PM
> Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes
>
>
>> On 7/13/2012 12:09 PM, ZR wrote:
>
> Thats correct at UHF and up but what is the error you have actually measured
> at 1.8 MHz?

The errors involved are NOT limited to UHF -- I've observed serious 
errors in the lower HF spectrum (i.e., below 10 MHz). It's why Chuck 
thinks the resonance of his chokes are as low as they are -- in reality, 
they resonate at a much higher frequency. And the errors are even 
greater with higher Q materials like #61.

>> Quoting from Wes Hayward on the subject of measuring high impedances:
>>
>
>
> >From a quick glance thru that paper I dont see much benefit of RF I-V below
> about 100MHz. What am I missing here?

These are not simple issues. It takes far more than a quick glance -- 
you need to STUDY this stuff.  I've provided some excellent references 
that are worthy of the effort. The issue is NOT the FREQUENCY of the 
measurement that causes the error, it is the fact that the magnitude of 
the impedance differs so much from 50 ohms. Wes is measuring at VHF, but 
I'm mostly measuring from 160M up to 10M.

73, Jim K9YC