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Re: LF: Re: 9kHz noise level

To: <[email protected]>
Subject: Re: LF: Re: 9kHz noise level
From: "James Moritz" <[email protected]>
Date: Fri, 26 Feb 2010 17:51:24 -0000
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Dear Markus, LF Group,

I checked the noise level again during the daytime, and the noise level was about 6dB lower than last night, i.e. about 13uV/m per sqrtHz

One possibility for the discrepancy between results is that the effective height of your antenna is reduced at VLF compared to the LF calibration point. In my transmitting vertical field strength measuring sessions on 500k, 136k and earlier 73k, the Heff of the same antenna works out consistently less as the frequency is reduced. I think this is due to increased "site loss" due to surrounding trees at the lower frequencies. H-field sensing loop antennas can be expected to be less affected. Of course, if there are no trees near your antenna, that theory is blown out of the water...

Cheers, Jim Moritz
73 de M0BMU



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