[Elecraft] BL2 choking Impedence measurements?

[w5ov at w5ov.com]

Jim,

Please allow me to add some facts about the AIM4170C to this discussion.

First, the AIM4170C is not designed only for "measuring impedances
relatively close to 50 ohms".

>From WX0B:

The AIM4170C can measure 50K ohms R and +/- 50K ohms X easily.

The fact is is that the higher the impedance, as you know from your work
with the Type 31 cores, even 1pf or .5pf of stray capacitance can
drastically affect the measurement.

So the test fixture must be carefully built and calibrated to get a
precise measurement. The AIM4170C or even an HP 8753 would have trouble
with a choking reactance measurement in a 5K+ environment.

Jay

73,

Bob W5OV
Array Solutions
(P.S. Both Jay and I own K3s now).

> On Wed, 25 Aug 2010 11:19:15 -0700 (PDT), Dennis KB7ST wrote:
>>I have the AIM 4170 antenna analyzer ( w5big.com ).  I could sweep the
>> balun
>>in 1:1 and 4:1 mode is you'd like.  I'm not sure it will give you the
choking impedance but will do some checking with the designer of the AIM.
> I don't own an AIM, but I've seen choke measurements made by an AIM that
had
> serious errors. A good common mode choke should have a high resistive
impedance at the frequencies where it is used, and the AIM is best suited
> for
> measuring impedances relatively close to 50 ohms (that is, within 1:5 or
5:1). It's fundamentally unsuitable for measuring the high impedances of a
> good choke.
> 73, Jim Brown K9YC
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