Topband: Slightly OT - amplifier noise

[Greg - ZL3IX]

I used one of these systems (homebrew WA1ION) for a  couple of years in 
the early 2000s. My problem was a speed-controlled water pump (local 
water authority) very close to my QTH. The pump was in the same 
direction as most of the wanted DX, so a nulling loop didn't work.

What I did was to erect a sense antenna as close as possible to the 
noise source and run the noise signal via a coax to the WA1ION box in my 
shack. Since the sense antenna was close to the noise source, the noise 
was very loud and could be (had to be ) attenuated before summing with 
the signal from the main antenna. The wanted signals picked up by the 
sense antenna were also therefore attenuated, and did not subtract from 
the wanted signals picked up by the main antenna.

I was able to achieve a very useful 10-12 dB of S/N improvement using 
this technique.

73, Greg, ZL3IX

On 2020-03-15 11:17, Richard (Rick) Karlquist wrote:
>
> I am trying to understand what these noise cancelling
> schemes do that couldn't be done with a simple loop
> (rotating the loop until the noise drops into one of
> the null directions).
>
> Rick N6RK
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