[Elecraft] Hum on KPA1500

[Jim Brown]

On 4/5/2020 1:50 PM, Carl Yaffey wrote:
> I have developed a loud hum with the KPA1500 on 17m and 15m. A slight hum on 20m. All other bands, no hum.

Because it's frequency dependent, I suspect some form of RFI. Start by 
making sure that everything in your station is properly bonded.
http://k9yc.com/GroundingAndAudio.pdf

If that doesn't fix it, add ferrite chokes as described in 
http://k9yc.com/KillingReceiveNoise.pdf

While the second reference is about killing RX noise, the same 
principles apply to the problem you're having.

But do the bonding first.

One question though -- is what you hear HUM (pure 60 Hz) or BUZZ 
(triplen harmonics of 60 Hz, like 180, 360, 540, etc)?

73, Jim K9YC