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[CQ-Contest] re:Clicks-REAL numbers.

Subject: [CQ-Contest] re:Clicks-REAL numbers.
From: hwardsil@WOLFENET.com (Ward Silver)
Date: Sun Mar 11 10:26:24 2001
These are good reasons to try a swept receiver test for the really
close-in performance measurements.  My original suggestion was intended to
measure out in the +/-20 kHz areas in which people were reporting clicks,
which I felt were less likely to be receiver-generated than the ones
within +/-5 kHz.  This measurement would be acceptably performed by the
141/855x analyzers.

A contest-grade HF receiver is designed for optimum performance in the
close-in environment.  Unfortunately, it doesn't lend itself to use as a
data acquisition system.  I suppose a simple program could be written to
step a receiver slowly across a keyed carrier and the AGC level measured
(assuming a calibration between AGC voltage and received input level with
a the same keying rate).  It's a pain unless you have access to a swept
receiver system, such as for EMI certification labs.  Or maybe have lots
and lots of spare time...

I think George's comment of a couple days ago (and echoed by Tom) is
probably closer to the root cause.  Applying steep rise time waveforms to
crystal filters is likely to cause spurious responses due to transient
characteristics.  Many of the original reporters have also observed that
the clicks change in nature, or disappear, with attenuation. This also
points to receiver artifacts.

73, Ward N0AX

 > Even a pure unmodulated carrier, absolutely stable, showed well
 > over 1 kHz of bandwidth at -50 dB when I used the 100Hz
 > bandwidth setting of my 141T analyzer and the best plug-in I
 > had...a 8553B!!!!
 > 6.) When I measured the same equipment on a Sierra Selective
 > level meter, there was a big difference in occupied bandwidth! A 5
 > mS rise and fall on my signal generator went from about 2 kHz BW
 > down to about 300 Hz BW at -50dB when I switched measurement
 > instruments!
 > 7.) When I listened on a receiver, it agreed with the Sierra  level
 > meter and disagreed with my HP-141T / 8553B.
 > Respectfully, I think the 141T and whatever plug-in we might have
 > can not be used to measure what we are trying to measure. We
 > are better off to use our receivers than something like a 141T.
 > I certainly trust George's integrity, but I don't trust his HP-141T at
 > all in this application. It is a poor instrument for the job.
 > 73, Tom W8JI
 > W8JI@contesting.com 

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