[Elecraft] BL2 choking Impedence measurements?

[Wes Stewart]

I am reminded of a time in my career when I was a member of a Components and Materials Department. We had experts in a variety of fields including, failure analysis, NDT, chemists, materials scientists, metallurgists, etc.  I was the RF/uW guy and had a “private” lab with over a mega-buck worth of HP test equipment in a shielded room.

The components guys were of course experts in that field and were also the guys who wrote a lot of specifications. I often got roped into this as well when RF parts were at issue.

It drove me bonkers when a missile program would say for example, a feed-thru filter needed to be specified over the frequency range of DC to X-band, simply because the missile operated at X-band.  If you want to know frustration, try telling a manager, or worse a government contract person, that measuring a power filter with foot-long shielded leads at 12 GHz is a really dumb idea.

Equally silly (and applicable here) is measuring a device in a 50-ohm environment and trying to determine attenuation, when in actual operation, neither the source or load impedance is known.

--- On Sat, 8/28/10, Ian White GM3SEK <gm3sek at ifwtech.co.uk> wrote:
 
> I measured the same chokes in both types of test jig,
> reflection and 
> transmission, and neither method has any clear advantage
> over the other. 
> Both methods have potential problems with variations in
> series 
> inductance and shunt capacitance (the latter in parallel
> with the 
> choke). In both cases, everything depends on the care taken
> to maintain 
> the test jig in exactly the same geometry, first for
> calibration and 
> then for all subsequent measurements.