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Cc: "<rsgb_lf_group@blacksheep.org>" <rsgb_lf_group@blacksheep.org>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
Date: Fri, 31 Dec 2010 18:23:08 +0000
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
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Subject: Re: LF: VLF - G3XIZ
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Reply-To: rsgb_lf_group@blacksheep.org


Congratulations Chris! I will have to add this new UK VLF record to my sub=
-9kHz webpage. If Jim can copy then I should be able to as well with a bet=
ter set-up. So pleased for you. Brilliant.

73s
Roger G3XBM

Sent from my iPod Touch 4g

On 31 Dec 2010, at 17:45, "James Moritz" <james.moritz@btopenworld.com> wr=
ote:

> Dear Chris, LF Group,
>=20
> The signal disappeared some time around 1520utc - the complete trace is=
 shown in the attachment.
>=20
> I made an estimate of the field strength of your signal by injecting a=
 test signal at a known EMF into the loop antenna, and comparing with the=
 level of your signal. The received FS at the strongest point (around 1330=
utc) worked out to be 1.8uV/m. Taking the distance between our locations=
 as 37km, your ERP would have been 87uW. The SNR at best was around 15dB,=
 making the noise level 0.32uV/m in the FFT noise bandwidth of 2.1mHz, or=
 a noise density of 7uV/m per sqrt(Hz)
>=20
> Assuming a 50m vertical wire (heff ~ 25m),  Rrad of your antenna at 8.97=
kHz would be 880micro-ohms. Assuming 2.62dB directivity for an electricall=
y short monopole compared to a dipole, and Iant of 200mA, the calculated=
 value of ERP would then be 64uW. So there is reasonable agreement between=
 these two calculations, the difference only being 1.3dB.
>=20
> Thanks for the tests,
>=20
> Cheers, Jim Moritz
> 73 de M0BMU=20
> <Dec31_08.jpg>