The PM-3 and other direct conversion receivers all suffer from something
called common mode interference when used with an AC supply. The easiest way
to eliminate this problem is to use lantern batteries with the PM-3. If you
want to use an AC supply, I think there's a way you can use ferrite torroids
on the power leads to block the hum. There's a technical explanation of why
this hum occurs. Check back issues of the Handbook and old QSTs. I recall
reading about it somewhere.
73, Winston K4CWQ
----- Original Message -----
From: George Maier <gmaier@ultranet.com>
To: Ten Tec Refelctor Post <tentec@contesting.com>
Sent: Tuesday, March 28, 2000 12:23 PM
Subject: [TenTec] PM-3 Hum problem
>
> 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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