Message-ID: <00c401c2f8f1$03937f40$a3e4fc3e@l8p8y6>
From: "hamilton mal" <g3kev.ham@virgin.net>
To: rsgb_lf_group@blacksheep.org
References: <HHEPIAAHNNPHBMLIALEMIEINCGAA.g3wkl@btinternet.com>
Date: Wed, 2 Apr 2003 08:08:24 +0100
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Subject: LF: Re: Re 73kHz Tuesday
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----- Original Message -----
From: "John W Gould" <g3wkl@btinternet.com>
To: "Rsgb_Lf_Group@Blacksheep.Org" <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, April 01, 2003 8:57 PM
Subject: LF: Re 73kHz Tuesday


> Plenty of activity, with approx sig level above estimated avg noise here
in
> Newport Pagnell:
>
> G3AQC 30dB
> G3LDO  30dB
> G3XDV  20dB
> G3GRO  20dB
> GM0MRF 10dB
>
> Saw some other transmissions, but wasn't around at the right time to get
> callsigns (apologies to G3YXM and MI0AYZ)
>
> My normally high noise floor "switched off sometime after 9am, dropping
the
> noise floor down from a stead S9 to a more normal sound, varying around S2
> with occasional crashes up to S7.  All of the signals above were audible,
> That of G3AQC and G3LDO moved the S-meter to an S5.
>
> My own transmissions were carried out from the house via a 100m length of
> coax to the loading coil and aerial.  Interestingly, last month when the
TX
> was in the shed next to the loading coil I got an aerial current of just
> under an amp.  Today, with two toroidal transformers (to first transform
> from around 4 ohms to 50ohms, and then from 50 ohms to around 200ohms - a
> guess at matching the aerial), the aerial current all but disappeared.
That
> might explain why, despite CQs during the morning, afternoon and early
> evening, I was only heard and worked by G3XDV.
>
> Much of the above will no doubt raise knowing smiles from you "old hands",
> but an interesting day for me and some thoughts as to what to do next.
I'd
> really like to know the source of the noise; it's unlikely to be TVs since
> it was still quiet at 8pm....

Hi John
One QRM source these days is the prolific use of energy saving light bulbs.
These are fatal in some cases for the LF operator. They seem to modulate the
mains, which carries the QRM around the neigbourhood, even at great
distances beyond the source, especially if you are on the same phase.
This type of qrm can appear on any low freq and unfortunately 73 or 136 khz
are within the spectrum. It appears as wavy lines spaced 100 hz apart on a
frequency and can be very severe. I experienced this type of qrm once and
was able to locate the source several hundred yards away f rom the antenna
and when the offending bulbs were changed, problem solved. It did not effect
the higher freqs like 160 metres, only down on the lower freqs.
It is probably going to get worse in the future with dirty mains problems
caused by smpsu's, the above light bulbs and all the digital devices coming
more popular.
Hope you get it solved.
73 de Mal/G3KEV

>
> 73 and nice to hear/see the good signals on the band.
>
> 73 John, G3WKL
>
>
>
>