[TenTec] PM-3 Hum problem

[Robert Weingaertner]

Many direct conversion receivers have a hum on receive when
using an AC supply. Its caused by some common mode noise that
gets into the detector and is amplified by the high gain audio stage.
Different antennas may help or hurt, but this is basically a 
characteristic of the direct conversion design. Similar receivers
like the Heath HW-7 and HW-8 will do the same thing. To fix it,
try winding two wires through a toroid core and connecting them
in series with both power leads. The best fix is to run the rig 
on a battery.


			73, Bob WB2VUF
George Maier wrote:
> 
> Hi T-T fans:
> 
> This may have come up before, so I'll apologize in advance.  My PM-3 has
> a very pronounced hum on receive.  The hum appears to get stronger when
> peaking the receiver tuning control.  It is independent of power
> supply.  I've tried it with my 961, an Astron VS-35, and a cheap Radio
> Shack thing; all the same.  I would guess that it's time to start
> replacing electrolytic caps, but before I shot-gun it, I was wondering
> if any one else had been down this same road.
> 
> Thanks for the read
> 
> George Maier - K1GXT
> 
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