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Message-ID: <5.1.0.14.0.20030108191419.0246d878@gemini.herts.ac.uk>
Date: Thu, 09 Jan 2003 10:56:04 +0000
To: rsgb_lf_group@blacksheep.org
From: "James Moritz" <j.r.moritz@herts.ac.uk>
In-reply-to: <00d201c2b736$1bdbc5a0$b930fd3e@default>
References: <29BDD4F529FCD311B631009027357C4E04D6A01C@btss103a.swh.sk>
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Subject: Re: LF: LFA 520
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Dear Tracey, LF group,

At 16:50 08/01/2003 +0000, you wrote:
>John Wilson did a comparison test in the Nov 2001 Short Wave Magazine
>between the RF Systems 520 and the Wellbrook Communications LFL1010 VLF loop
>antenna and the 520 was well beaten by the 1010 .
>
>http://www.wellbrook.uk.com/LFL1010.html
>
>The SWM review of the 520/1010 and John's savage comments about the 520 can
>be found here! :-)
>
>http://www.wellbrook.uk.com/reviews/SWM2001Nov.html

Looking at this review, it does not actually contain the information you 
really want to know for a receiving antenna, ie.is the antenna noise floor 
below the band noise level?. Unless that is true, it would not be much use 
for weak signal reception. However, the reviewer does compare the SNR when 
receiving what appears to be DCF29 (DBF29?) on 128.93kHz (see fig 3 and the 
paragraph above), and on the LFL1010 (the better of the two), gets an SNR 
of 33dB. I usually find this signal is 50 - 60dB over the band noise (in 
300Hz BW - the bandwidth used in the test also does not seem to be stated), 
so it looks like this antenna has rather poor sensitivity, even though the 
reviewer likes it. The tests seem to have taken place near Exmoor, so 
somewhat further from DL than me, but I would not think far enough to 
reduce the signal level by 20dB. I suppose it is possible the transmitter 
was running lower power that day, but "Caveat Emptor", as Mr Wilson says!

Incidentally, the stuff about having to mount an E-field antenna on a 
grounded metal pole is a bit peculiar - so long as the feeder is grounded 
somewhere, it should be happy. Also the idea that local noise is 
predominantly E-field is certainly not universally true, and at LF, in my 
opinion, probably a myth.

Cheers, Jim Moritz
73 de M0BMU