[TenTec] Model 963 questions

[Richards]

Hmnm..... the plot "sickens...."


1)  Ferrite beads on the DC leads have no effect.

2)   AC Isolalation transformer (even on different AC lines) - no effect.

3)   Turning the mobile rig  (Yaesu FT-2900)  off makes the whole
	mess BUZZZZZ louder, until I jiggle its DC power cable.

NOTE - there is an MFJ-1112 DC power strip (uses binding posts) between 
the power supply and the FT-200, scanner, TT-RX320D.    I wonder if that 
is part of the problem . . .  Hhmmmmm....

Driving me batty, as I have not had ANY noise in the shack since Bob 
K4TAX suggested snugging up all my connectors nice and tight.

---------------
Happy Trails.
=======================  Richards / K8JHR  =========================

On 9/20/2011 16:49, Stuart Rohre wrote:
> 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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