It is probably the way you are coupling the spectrum analyzer to the
radio. How are you coupling it to the radio when the antenna is on the
radio?

If you are just using the antenna on the spectrum analyzer you could
be seeing anything.

You may be overloading the analyzer. It is difficult to see down that
far and not overload the analyzer with the wanted signal. Try
switching in a 10 db attenuater at the front end of the analyzer. Do
the spurs drop 10 db? If they drop more you are overloading the
analyzer.

You mentioned connecting the radio directly to the analyzer. If the
analyzer is an IFR service monitor or another service monitor then all
bets are off as to what you are seeing. They are poor spectrum
analyzers.

73
Gary K4FMX


On 29 Apr 2004 00:34:31 -0700, (Dummy) wrote:

I'm having a two-way radio. One wide-band antenna was hooked up on a
spectrum analyzer. Video BW and RES BW was adjusted to 3khz and 1kHz
respectively at spectrum analyzer. Span was 300KHz.

When radio was being keyed up, spurs could be seen at around plus
minus 32Khz and 62khz. However, the amplitude were quite low, about
-65 to 70dBc. I was wondering what caused the spurs to appear. If
radio was connected directly to spectrum analyzer, this problem could
not be seen.

When radio was transmitting to different load with different VSWR (up
to 8:1), no spurs were seen. Spurs could only be observed while using
antenna. Could the VSWR of antenna be worse than 8:1? Just could not
figure out the source of the spurs. Please help.