LF: Man-made Noise]

[Andre' Kesteloot]

Interesting observations about man-made noise
Andre'
************************************
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
> Publications Manager
>
> * RadCom * Ham Radio Today * RSGB Books *
> * GB2RS News * RSGB On-Line Web Site *
>
> Radio Society of Great Britain
> Lambda House, Cranborne Road
> Potters Bar, Herts UK, EN6 3JE
> E-mail: publications@rsgb.org.uk
> Tel: +44 (0) 1707 659015; Fax: +44 (0) 1707 645105
>
> RSGB - UK AMATEUR RADIO