The flickering pilot light makes me wonder if it is a neon lamp in an
off on switch?
The neon AC operated lamps are notorius for getting to an age where they
are photo sensitive to room lights, and also for getting to where they
flicker. This indicates the gas has been diluted or leaked, and the
only recourse is to replace the switch if the lamp is non removable.
I have thought about cutting into the switch to wire in a leaded
replacement NE 2, but have not gone to the trouble on some I have had go
that way.
As long it is flickering, you know it is on. It is actually doing a
relaxation oscillation at the flicker frequency.
The UHF oscillation on the other hand, is likely a switcher power supply
artifact. Switchers are oscillators first of all. If they don't have
DC to daylight filtering, they may produce some hash. You could try
putting the switcher power supply on a different AC circuit from the
radio. Or, if you can find a very good AC input side filter, one that
filters both hot and neutral sides of the AC line, that might introduce
another 20 dB of loss at HF/UHF, and keep the 850 MHz bottled up inside
the switcher. Also check that the covers are on tight, if a metal box,
and paint is not compromising the grounding of overlapping joints.
Ferrite beads might be tried on the output DC leads, if not already
there. (Internally).
Don't know of ham activity up there where you found the artifact, but
maybe you have a scanner you use. In that case, it would be the scanner
that must be separated from the switcher power source to isolate them.
Most of the ham market switchers, if filtered, are mainly suppressed in
the HF ham bands. It is really hard to build one that is bulletproof,
however.
-Stuart Rohre
K5KVH
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