One aspect of this discussion is an observation such as "XYZ bulbs don't
generate noise in my receiver" is fine for stations which are not
attempting to transmit on one band, while listening on another. For
multi-op or SO2R contest stations, the requirements are considerably
more complicated.
Several contest operators have discovered that many LED (and also CFL)
bulbs become active P/N junctions in the presence of intense RF energy.
This is a common occurrence in multi-op or SO2R stations. The resulting
"flooding" of P/N junctions can cause wide-band noise which can often
wipe out one band, while transmitting on another.
Testing this scenario requires the bulb(s) to be installed at the QTH.
Then, while transmitting on one band, the other bands must be checked on
a spectrum analyzer. Such tests are considerably more time-consuming, as
each band combination must be tested thoroughly. A handheld analyzer
such as the Tiny SA and a portable sense loop can prove useful for such
tests.
—Kirk K4RO
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