[Elecraft] AC hum on tune

[Mike WA8BXN]

Did you try running your monitor receiver on battery?

73 - Mike WA8BXN

 
 
-------Original Message------- 
 
From: Sam Morgan 
Date: 5/16/2010 8:03:33 PM 
To: Tom W8JI 
Cc: elecraft at mailman.qth.net 
Subject: Re: [Elecraft] AC hum on tune 
 
Well at this point I have: 
Gone on battery power 
Nothing is hooked up to the K3 
Except the 12v power lines from the battery 
 
All reports of a hum on my tune signal 
Have come from stations 1/2 mile to 3 miles away 
My output power was varied from 1w to 100w 
Only difference was the hum was louder with more power 
 
One station 75.5 miles away did not hear the hum however 
The 80m band was QRN with storms and local noise at the rx station 
 
Clues?: 
Hum is louder on 80m than on 17m 
Nothing different if I go to battery or on ac/dc power supplies 
 
At this point I think for my next try 
(since I have been using it on SSB only so far) 
I will get on cw and see if I can get any R5 S9 T(1-6) reports 
If I don't I will quit freaking out and be satisfied for now. 
 
If that is successful I will start adding things back to the rig 
Ground, serial cable, line out, (external) tuner, IF output cable, 
Amp and keying line to amp, ground to amp, coax switch, 
Ground to coax switch, other antennas to coax switch, etc etc etc..... 
 
Hmmmmm lots of *stuff* involved when you get back to that point 
Hopefully somewhere along the way, 
Something will show it's self as the culprit 
 
Thanks to all who have offered suggestions on and off list. 
-- 
GB & 73 
K5OAI 
Sam Morgan 
 
 
On 5/16/2010 3:03 PM, Tom W8JI wrote: 
 
> It is common for me to hear hum or buzz on local receivers very near a 
> transmitter. Even on perfectly clean transmitters unless I use a line 
> tap to sample signal all sorts of stuff mixes in. I've never really 
> looked into why. My guess would be it is some nasty multipath being 
> modulated by something. Just a guess. 
> 
> I'm not saying you don't have hum, but just cautioning you to be careful 
> when listening on a local receiver near a transmitter. I can replicate 
> hum on my shop receivers even with a very clean transmitter on the bench. 
> 
> That aside, did you try disconnecting everything except the K3 antenna 
> and power supply? 
> 
> Switching supplies do not normally cause 60 or 120 Hz problems. 
> 
> 73 Tom 
> 
 
 
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