LF: Man-made Noise]
Mon, 25 Jan 1999 19:50:37 -0500
Interesting observations about man-made noise
Mike Dennison wrote:
> Regular subscribers to this group will know my grumbles about
> receiver sensitivity. Until recently, I was able to optimise my
> receiver to get a really good signal to noise ratio. Occasionally I
> would get white noise centred just below 136kHz and spreading all
> over the band at S9 - still not identified but believed to be a light
> bulb or dimmer.
> However, this Christmas, my neighbours seem to have received
> lots of high tech presents. It is very rare that I can get down to the
> Loran noise, and often the local noise is S9+ all over the band. I
> can reduce this by using a loop antenna but only when there is a
> single noise source. Often there are two or even four sources. I
> tried to use a separate receiving antenna at the far end of the
> garden away from the houses but this was not effective.
> I did find the cure for one of these - my own television. The
> interference - white noise which raised the noise floor to about S5 -
> was radiated from the outer of the antenna coax. This cable runs
> vertically up the front of the house, 25ft from where the antenna
> runs vertically up the back. The fix was to install a crude braid
> breaker, ie I put 100pF capacitors in series with both the outer and
> inner of the coax, low Z to UHF but high Z to LF.
> Now to persuade my neighbours to do the same . . . .
> If you regularly give much poorer reports than you get, try taking
> your radio out in the car and, using a loop antenna, just check out
> the s/n ratio available away from towns. You may be surprised at
> what is achievable if only the man-made noise was silenced.
> Has anyone else had any success in reducing man-made noise? Is
> a noise canceller effective with more than one source?
> Mike Dennison, G3XDV
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