[TenTec] Model 963 questions

[Stuart Rohre]

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