Jim,
Agreed - that's why I deliberately chose a choke wound on #61 material
to do the measurements - the higher Q resulted in more pronounced shifts
of SRF with stray C.
Given the importance of having resistive (lossy) chokes, I wonder how
you determine the phase angle using your test set-up?
73,
Steve G3TXQ
Jim Brown wrote:
> YES. And that is exactly why the #61 material is a very bad choice -- a
> high resistive impedance can be achieved for a relatively small frequency
> range. For most of the spectrum it is either inductive or capacitive, and
> can be cancelled by the common mode reactance of the transmission line.
>
> The #43 material achieves this above 5 MHz, and the #31 material achieves
> this from the AM broadcast band up to VHF.
>
> Another way of looking this is that chokes wound with #61 have Qs on the
> order of 10, while HF chokes wound with #31 or #43 have Qs less than 0.5.
>
> 73,
>
> Jim Brown K9YC
>
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