Re: Getting a buzz, the wrong way

Posted by Jim Brown-10 on Jan 11, 2011; 11:50pm
URL: http://elecraft.85.s1.nabble.com/Getting-a-buzz-the-wrong-way-tp5901644p5912933.html

On 1/7/2011 7:04 PM, Tony Estep wrote:
> If you have a wire antenna, disconnect it, put 50 ohms across the coax and
> hook it to your scope. If you are like me, you will see a hideous waveform
> of mixed harmonics of 60 hz,

If you see a lot of 60Hz and its harmonics on a scope as you have
described here, I would STRONGLY suspect a "pin 1 problem" in the scope.
The most common form of a Pin 1 Problem is the mis-connection of a cable
shield to internal circuitry rather than to the equipment chassis.
Another common form is the connection of the power system equipment
ground (the Green wire) to internal wiring, rather than to the chassis.

With either (or both) of these design errors, any current flowing on
either or both of those leads (the cable shield and/or the green wire)
flows through the equipment, creates a voltage drop on that wiring that
is added to the signal path and amplified. If it is modulated RF, it is
often detected, and is a common cause of RFI.

73, Jim Brown K9YC
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