A spectrum analyzer or a tranceiver with a spectrum display can allow
you to see interference you might not hear on a receiver without a lot
of tuning around. Most RFI is composed of one or more discrete
frequencies, but they may be very unstable. The one that was at 13.950
when you listened on 14.050 might drift into the band at some time.
I'm not sure any receiver or SA is likely to hear "band noise" with a
very small, untuned antenna. A good test would be to see if it can hear
any of the weaker signals you can hear with a larger antenna.
73,
Scott K9MA
On 7/8/2025 6:52 PM, Richard Karlquist wrote:
For antenna measurements with a spectrum analyzer, if you have a fairly
efficient receiving antenna, the preamp will typically overload, and in
addition you may have to add attenuation. I suspect that anything
described as "tiny" does not have a high dynamic range preamp. If you
connect a short whip as an antenna, the noise from the preamp will
dominate and you not be able to hear over the air noise. Any ham type
radio receiver will run circles around a spectrum analyzer for the
purpose of this test. We all own one or more of those; why not use
them? An SA is simply the wrong tool.
--
Scott K9MA
k9ma@sdellington.us
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