Re: LF: VLF - G3XIZ

["James Moritz" <james.moritz@btopenworld.com>]

Dear Chris, LF Group,

The signal disappeared some time around 1520utc - the complete trace is 
shown in the attachment.
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 1330utc) 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)
Assuming a 50m vertical wire (heff ~ 25m),  Rrad of your antenna at 8.97kHz 
would be 880micro-ohms. Assuming 2.62dB directivity for an electrically 
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.
Thanks for the tests,

Cheers, Jim Moritz
73 de M0BMU

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