Topband: Clicks-REAL numbers

[Bill Tippett]

        Since not all of you read the CQ-Contest reflector, I'm 
posting W2VJN's measurements here:

Here are some keying test results done with real radios and an HP spectrum
analyzer.  The radios were set up at full output power and were keyed at 40
WPM.  The spectrum analyzer was setup with a narrow bandwidth and very slow
sweep time.  The dB levels given were measured at an offset of 1 kHz on each
side of the carrier.  (Total bandwidth = 2 kHz.)

Radio        dB down at +/- 1kHz

Omni VI+           -50
1000MP             -46
IC765              -44
Test               -51

The Test was done with an HP8640B signal generator keyed on and off at 40
WPM with a rise and fall time of 5 mS.

This data shows that there really are sidebands out there which will be
heard by adjacent channel receivers.  This is a fact of life.  For example:
An Omni VI+ is sending 40 WPM and is S9 +30 dB on tune.  One kHz away his
sidebands (clicks) will be down 50 dB, or about S6 to S7 on a calibrated
meter (not a typical S meter).  Since the receiver filter also has a finite
bandwidth even with the best filters, the transmitted signal will appear to
be even wider.  This assumes there is no blocking or IMD taking place in the
rx or excessive phase noise in either tx or rx.  If there is, he will appear
wider yet.

It's interesting to me to see how little difference there is between these
radios.  Thanks for the suggestion N0AX.

George, W2VJN


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