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Re: LF: Antennas

from [Roger Lapthorn] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: Antennas
From: Roger Lapthorn <[email protected]>
Date: Wed, 3 Aug 2011 20:01:01 +0100
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Mal

You may be right about big antennas in a decent, quiet rural location but the majority of us now live close to modern civilisation with noise floors that have risen some 20-30dB or more at the lower end of the spectrum in recent years.

Top Band is almost unusable here and 80m not a lot better. I am surprisingly lucky on 500kHz and 136kHz where I seem to be able to hold my own on receive with my loop antenna in its favoured directions. Many get very good results with PA0RDT type E-field probe antennas with careful location and after efforts to minimise noise pick-up. In the end S/N is all that matters so having a large antenna which increases both wanted signal and noise has no benefit as long as the S/N is as good as it can be.

With more and more difficult noise environments in most urban and semi-urban locations I can see many people giving up amateur radio below 432MHz.  I am tempted more and more to move up to the UHF and microwave region to get my next challenges and I live on the edge of a village where the noise must be far less of an issue than for my city friends.

A little more understanding of the plight of many LFers in busy cities and some encouraging words and ideas would be good Mal.

73s
Roger G3XBM



On 3 August 2011 19:08, Chris <[email protected]> wrote:
Hi Mal and LF,
Well, all I can say is that here the signal to noise ratio on RX is better on my PA0RDT than it is on my long wire (inverted 'L'). I have always thought this a bit strange, quite often weak signals that cannot be seen on the wire are perfectly copied on the PA0RDT. This applies from 136kHz to 3.8MHz. I cannot see what else it can be other than local noise/QRM level. 80m is another prime example where the noise has gradually got worse over the years here.
Vy 73,
Chris, G4AYT, Whitstable, Kent.



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