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Re: Question about interaction between separate  rigs...



As a result of last night's experiments:

I'm beginning to believe the problem is related to, of all things, the headphone/external speaker jack on the -290RII.  The problem is non-existent when transmitting on the 70cm, any mode, and listening for it on the 2M internal speaker.  When I insert a headphone plug into the 2M external phones jack, the interference starts up.  using an insulated stick (a piece of wooden yardstick) to divorce my hands from the vicinity of the 2M rig's case, I can wiggle the headphone plug about in the jack a little bit and the interference changes in strength and quality when I do so.  If I push the plug off-axis in the upward direction, the interference nearly drops off to nothing.  Thinking that there was something to the length of the headphone cord, some weird resonance thing, I swapped with a couple of other pairs -- no difference.  I then wrapped about a dozen loops of cord from a pair of walkman-styles around a snap-open toroidal choke to see if that would help -- no joy there, either.

BTW, no change in anything when transmitting 70cm RF into the 7-el Arrow Yagi and receiving with the 2M antenna connection terminating in a 50ohm dummy load.

I consulted the schematics again and concentrated on the AF amp, Q4009, section of the -290RII, looking for potential trouble spots.  Admittedly, I'm not big on going inside, and did not see anything in the schematics that would suggest looking inside more than I have.  I learned by opening up both the top and bottom plates on the 2M rig is that the external speaker jack is obscured by boards from both above and below; there was no way to tell if a connection was obviously amiss or out of norm.  Is it possible that something that should be grounding isn't or that something that shouldn't be grounding is, somewhere in the AF amp?

Thanks, again, everyone.  Great advice all around.
73, Ray KA8SYX
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