[TenTec] Model 963 questions

[Richards]

I might have traced the buzzing down to the FT-2900.

*   It stops if I unplug it.

*   It gets worse and the buzzing "warbles" (oscillates?) when I
      only plug in the red or the black wires, alone.

*    It gets worse when the radio is unplugged... but stops if I
	disconnect the antenna cable.

*    It  buzzes even if I bypass the MFJ power distribution strip.


Any traction ?

I am mindful of the old joke...
      Doctor -    "Does it hurt?"
      Patient -   "Only when I do this..."  (gesturing)
      Doctor -  "Well... don't do this.?"



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

On 9/20/2011 17:25, Richards wrote:
> 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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