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VLF: QRM?

To: <[email protected]>
Subject: VLF: QRM?
From: "hvanesce" <[email protected]>
Date: Fri, 27 Dec 2013 11:30:04 -0700
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Is the signal in the attached most likely QRM?

 

The amplitude has varied by only +/-5dB over a 24 hour period*, which makes me think that the signal is local (QRM).

 

The two frequencies exhibited by this signal are 12mHz apart, and stable within the < 1mHz stability of my sound card oscillator. It is the 12mHz frequency shift, sustained over a 24 hour period, that makes me wonder if the signal is something other than QRM.

 

Regarding uncertainty of absolute frequency: the signal is shown near 8972.81 Hz, but I do not know the offset of my sound card clock; my sound card clock and my low-accuracy reference clock differ by 0.3Hz (+/- 1mHz over short and long time intervals), so until install an accurate clock I can only guess that my clock offset could be +/-1Hz or so. Accordingly the center frequency of the signal shown here could be +/- 1Hz or so from the indicated 8972.81

 

At the moment I have only one antenna, pointed east-west [toward Tom(dj8)CAT et al], so I can’t rotate to see if the signal looks like a (distant) point source.

 

Is it most likely that the signal in the attached is QRM?

 

73,  Jim AA5BW

 

      *  +/-5dB over a 24 hour period with ~45 minute integration time – 358uHz FFT bin width  

 

Attachment: 131227 1547UT 8972.8 Unknown v2.jpg
Description: JPEG image

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