On 1/13/2011 2:16 PM, Roger (K8RI) wrote:
> why did it work for several years and then suddenly
> start picking up AC?
One possibility that some weak connection broke. Another is that some
new noise source was introduced into your shack. HUM (that is, pure 60
Hz) is usually the result of a magnetic field being picked up in system
wiring, as opposed to BUZZ (harmonics of 60 Hz), which is usually caused
by leakage currents from the AC power line setting up voltage
differences between the chassis of equipment that are interconnected.
See http://audiosystemsgroup.com/HamInterfacing.pdf
73, Jim K9YC
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