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Delivery-date: Fri, 10 Jun 2005 15:51:09 +0100
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From: "Laurence KL1X" <hellozerohellozero@hotmail.com>
To: rsgb_lf_group@blacksheep.org
Date: Fri, 10 Jun 2005 06:50:33 -0800
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Subject: RE: LF: Re: Unwanted LF radiation
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Being another Ex BT man (!) and having wandered thru the streets tracking 
down a) pirate radio stations but less interesting and more often b) faulty 
switchmode PSU's Im wondering whether you have a waterpumping station 
nearby, say within a mile . -

Some of these have very nasty motor phase controllers that are appauling and 
had a history of LF and in some case HF interference over a wide area often 
conducted by telephone and power lines. Ive seen peaks in the 100Khz and 
3Mhz regions and the noiz can be smooth or raspy, intermittent or near 
continuous.

Laurence


>From: "Alan Melia" <Alan.Melia@btinternet.com>
>Reply-To: rsgb_lf_group@blacksheep.org
>To: <rsgb_lf_group@blacksheep.org>
>Subject: LF: Re: Unwanted LF radiation
>Date: Fri, 10 Jun 2005 15:19:09 +0100
>
>Hi Howard, although an ex BT man I dont reckon to know anything about
>telephones really !! One thought occurs to me that in the past there have
>been problems due to faulty devices in terminals (instruments) radiating
>noise and / or oscillations from the lines.
>
>Assuming it is your own drop that is a problem, can you temporarily
>disconnect all equipment from your master socket, and then reinstall one at
>a time. I am thinking of telephone instrument problems rather than data
>units.
>
>If that is not the problem the other area I have found with wideband noise
>are fluorescent light particularly when the starter is getting a bit
>old.....some still strike after the tube is lit. This of course will not
>result in the noise being radiated by the drop.
>
>There is of course a BIG signal located at 100kHz which might be "showing
>through the noise" ....Loran-C. There were suggestions that BT would be
>starting up an experimental transmission this month but I have seen no 
>signs
>of this yet, and I guess you are about as far north in Skipton as I am to
>the south east  (Ipswich) of Rugby..... so we should see similar strengths.
>
>It might be easier to locate if there were some recognisable "lines", most
>noises I see are eithe 100Hz or 50Hz somewhere and be traced to a number of
>known causes. I find ARGO very useful for tracking these using the RX 
>audio.
>Both John G4GVC and Peter G3LDO have reported these kinds of noises before,
>but with no definitive source found.
>
>Cheers de Alan G3NYK
>
>----- Original Message -----
>From: "Howard Aspinall" <howard.adaire@connectfree.co.uk>
>To: <rsgb_lf_group@blacksheep.org>
>Sent: 10 June 2005 11:27
>Subject: LF: Unwanted LF radiation
>
>
> > This might be just a bit off the beaten track for the reflector, despite
>being LF orientated,
> > but I wonder if anyone has any useful observations or information they
>might pass on.
> >
> > Whilst tracking down some noise interference problems, I discovered
>sizeable amounts
> > of wideband RF between 75 and 130 KHz. This manifests itself as
> >  "smooth" noise. It extends outside these frequency parameters well into
>long/medium
> > waveband, and is radiating from the overhead BT telephone drop line.
>Broadband
> > internet RF seems the most likely culprit (there being a null between 
>130
>and 140 KHz),
> > but we do not have any broadband facility here.
> >
> > An HP spectrum analyser close coupled to the line (common mode) shows 
>this
>signal
> > level to reach at least 5 mV around 100 KHz.
> >
> >  Tests on BT lines in other areas where broadband is also not installed
>show no RF
> > present other than broadcast stations etc.
> >
> >  Can anyone say if such common mode RF levels on BT lines can be 
>typical,
>or might be
> > expected where no broadband facilities are connected? Are levels I am
>finding here
> > regarded as acceptable? And does anyone know of any regulations, codes 
>of
>practice
> > or technical standards on the subject?
> >
> > Howard   G3RXH
> >
> >
> >
> >
> >
> >
> >
> >
>
>