[CQ-Contest] Clicks

[Ward Silver]

The customary way of specifying spectral cleanliness is to create a
"profile" of level vs. frequency.  For an example, refer to the FCC
specifications for EMI type-acceptance.

The standard for spurious products used for ham equipment type acceptance
is something like "all IMD products must be -40 dB with respect to the
signal at 20 kHz from the signal frequency." (I'm grossly
oversimplifying...)  What we are looking for in this case is a similar
statement - "All transient products may have a peak amplitude no greater
than -x dB with respect to a CW signal's peak amplitude over a bandwidth
of +/-y kHz centered on the CW signal."

So, there is a standard, but it is focused on non-linearities generating
IMD products in the transmitter output.  It is not written with respect to
transient spurs generated by keying edges.  Since there is no standard,
there are no measurements taken.

73, Ward N0AX

 >  >I am curious if there are any standards for measuring click performance?
 > In other
 >  >words, how do you attach a number to a transient event like a key click?
 > N0AX
 >  >described a procedure for measuring key click performance using a spectrum
 >  >analyzer. How does one correlate the spectrum analyzer readings with 
what is
 >  >acceptable and what isn't? Obviously lower spurious readings on the 
spectrum
 >  >analyzer are better than higher ones, but how good is good enough? All our
 > rigs,
 >  >have finite phase noise, harmonics,  and IMD performance yet at some 
point we
 >  >say - "good enough" - its a clean rig.
 >
 > Very good question.  The ARRL Handbook points out that there is a
 > correlation between the rise/fall times of the RF envelope, CW speed and
 > intelligibility, with some degree of "hardness" being necessary to support
 > higher-speed CW.
 >
 > I've been told, however, that synthesizer anomalies produce "unnecessary"
 > clicks, and that the Omni 6+ is particularly clean -- if so, perhaps its
 > level of clickiness could become a de facto standard of comparison.
 >
 > 73, Pete N4ZR
 > Contesting is!


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