Envelope-to: dave@picks.force9.co.uk
Delivery-date: Wed, 25 Jan 2006 14:45:03 +0000
Message-ID: <013401c621bd$c7f33c20$2101a8c0@pcroelof>
From: "Roelof Bakker" <roelof@ndb.demon.nl>
To: rsgb_lf_group@blacksheep.org
References: <NKEMLGOEKANPNJOBFBAFGEKDCJAA.g4wgt@tiscali.co.uk> <016101c61d02$12ceca40$2101a8c0@pcroelof> <002b01c61d54$c510aaa0$20347ad5@w4o8m9>
Date: Wed, 25 Jan 2006 15:44:01 +0100
MIME-Version: 1.0
Subject: LF: Re: Re: Mini Whip and local noise
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Hello Jim, LF group,

Many thanks for your comments on my local noise report.

>> So one would expect predominantly "magnetic" noise from mains wiring. <<

That is what I thought as well. However, tests with a battery operated SPM-3 
SLM, showed that local noise on an outdoor E-field antenna is substantial 
less than on a magnetic field antenna.

I have also been testing this the other way round: reception of the carrier 
of DCF-39 and semi-local NDB's. Mounting a mini-whip on a bamboo pole and 
putting it outside an upstairs window, the signal of DCF-39 increases 22 dB. 
Whilst holding a talk for the local ARC in a concrete buiding, the same test 
was performed on 399.5 kHz. The difference was as high as 40 dB. One could 
reason that the same attenuation level applies for propagation of indoor 
electric fields to the outside world. So far my guess is that this explains 
the low local noise level on my E-field antenna, though it is mounted only 5 
metre from the house.

As we all know, magnetic field antennas, e.g. loops, do receive very well 
indoors. Thus the same reasoning applies for propagation of local noise in 
the magnetic field to the outside world: little if any attenuationa at all.

It should be nice if someone else could also perform these tests.

Best regards,

Roelof Bakker, pa0rdt