[UK-CONTEST] Rf in 'mp audio

[Justin Snow]

I find that RF gets in on the headphone lead and that a small toroid 
common mode choke helps on my MP5

Justin, G4TSH

On 20/10/2010 21:39, John Wayman wrote:
> Hello,
> I am hearing a huge thump in the headphones on the first character when I send
> CW on my old-school 'mp. It seems as if it kills the AGC, which then recovers
> after the first dash, or thereabouts. Funny thing is, it does it the same
> whether I use the sidetone or the monitor.
> No such problems if I use the built-in speaker, or if I connect an external
> speaker to the rear panel. Just the headphone socket.
> Have you seen anything similar, and, if so, how did you cure it?
> I am not aware that I have changed anything, or done anything I can point to as
> having made a difference.
>
> I wonder whether it could be related to the well-known intolerance of RF with a
> key plugged into the front panel key jack (I just never use it these days),
> although I don't see how.
>
> What I want is for someone to say 'You just solder a 0.01 across these points
> and it will be fine.' I don't think life is like that, though, is it?
>
> Any advice gratefully received (except trading it in against an FT2000, or 5000,
> or whatever!)
>
> In the meantime, I'll have a look at that part of the circuit diagram.
>
> 73,
>
> John
> G4DRS
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