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 <gm3...@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.
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