> Hmmm... we seem to be deep into the territory where "the more you claim
> to have achieved, the more you need to prove it."
>
>
> Tom added:
> >By the way, if the common mode source and load impedances are a fraction
of
> >an ohm it is easy to obtain -50dB. If the common mode source and load
> >impedances (which have nothing much to do with line impedance) are 1000
> >ohms, we would be lucky to see 10dB.
> >
> >It depends on how they measured.
>
> The standard method is to measure between a 50-ohm source and load - the
> input being to the coax shield at one end, and the output from the
> shield at the opposite end.
Standard schmandard.
People can measure things like this any way they like. I use a 50 ohm
network analyzer that has a 50 ohm source and load, but some CE tests or "do
it yourself" tests use other methods.
Not to flog this dead horse (I doubt they REALLY have 50dB CMR with a
50ohm/50 ohm test) further into submission, but they may also measure
without zeroing out effects of cable lengths. For example if I measure
attenuation without normalizing out connecting lines the results are
different than when the lines are not a factor.
My hunch is they just used a signal generator and a voltmeter, or some other
sloppy method. It's like measuring current in loading coils :-).
73 Tom
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