LF: RE: DLF passive received with earth antenna

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

Dear Stefan, LF Group,

It gets confusing when the bandwidth changes! In this case, both measurement 
bandwidths are much smaller than the modulation bandwidth, and the signal 
has a continuous spectrum,  so it is reasonable to assume the measured 
signal power will be proportional to the measurement bandwidth. The 
amplitude of the signal on the earth antenna was -20dB in 3Hz BW. To 
normalise the measurements to a 3Hz FFT BW, you need to add 6dB to the 
amplitude of the 1m^2 loop signal in 0.75Hz bandwidth, to give -94dB as you 
said.  The ratio of signal amplitudes is then 74dB, or a factor of about 
5000. So the eqiuvalent area of the earth antenna is 5000m^2.
Adding Markus' factor of 11dB to give the total signal amplitude from the 
1m^2 loop gives -83dB, 74 dB below your reference level of 44mV = -9dB. 
Therefore the 1m^2 loop EMF is about 9uV, corresponding to FS of DHO38 being 
about 18mV/m. If this is correct, it corresponds to about 1.1MW ERP, which 
is impressive, but since the signal is down in the noise in your system, 
these figures can only be a very rough estimate.
Cheers, Jim Moritz
73 de M0BMU

----- Original Message ----- 
From: "Stefan Schäfer" <schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, July 16, 2010 11:32 PM
Subject: Re: LF: RE: DLF passive received with earth antenna


> Ehm, 18000m^2? I have just calculated 5000m^2. It is A = 1m^2 * 
> 10EXP((-94--20)/20), right?
> 73, Stefan