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Re: LF: LFA 520

To: [email protected]
Subject: Re: LF: LFA 520
From: "James Moritz" <[email protected]>
Date: Thu, 09 Jan 2003 10:56:04 +0000
In-reply-to: <[email protected]>
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
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 .

The SWM review of the 520/1010 and John's savage comments about the 520 can
be found here! :-)
Looking at this review, it does not actually contain the information you
really want to know for a receiving antenna, 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

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