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Re: LF: Re: DK7FC's 7th VLF kite experiment

To: [email protected]
Subject: Re: LF: Re: DK7FC's 7th VLF kite experiment
From: Stefan Schäfer <[email protected]>
Date: Sat, 09 Oct 2010 21:00:49 +0200
In-reply-to: <2024E84F348A4A039481951F65394FA7@JimPC>
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Hi Jim,

This capture is taken from your home QTH, rigt? Or have you been out in your car for 24 hours, just to minitor? ;-) It looks nice and very clear with very low QRM, at least above 5 kHz. The spectrum curve is surely a mixture out of the VLF noise floor, your antennas frequency response and mains hum (just below 5 kHz). The MSKs are relatively low in its level but not in its S/N, due to your band limiting. You could easily lock your soundcard to GQZ at 22.1 kHz to make an quasi atomic accuracy RX out of it (but the drifting carrier of my 7th experiment was due to my upheating VFO and not due to your soundcard drift, so its all no problem).

There is sometimes a trace arround 10,6 kHz which looks as a MSK signal that cannot be there. I have observed the same line on my grabber. Do you have an idea what can cause this trace on this QRG? But its all not affecting the Dreamers Band! :-)

Since the signal (to noise) levels have been so strong in the last experiment, i think i want to try DFCW-120 the next time, not only but a part of the mesage. Seems to be no problem for you :-) I run F5WK's wav file in QRSS-120 mode and it was no problem at all to see the signal...

I have inserted a switch to change the range of the antenna amperemeter to 1A or 2A, so 6 dB more ERP is necessary to reach again the goal to bring the needle to the catch ;-)

73, Stefan/DK7FC


Am 09.10.2010 09:53, schrieb James Moritz:
Dear Stefan, LF Group,

Thie attachment shows just over 24h of VLF spectrogram recorded using the "wideband.usr" file you posted earlier. The period shown is 1200utc on 7/10 until 1200utc on 8/1, produced by editing 2 screen shots together.

The noise level about 0 - 5kHz is predominantly mains harmonics, on top of a continuum of noise that is due to impulses from an electric fence somewhere nearby. Some of the noise is probably internal to the PC. The baseline of the spectrum plot effectively shows the low frequency response of the antenna/preamp.

The range 5 - 12kHz is dominated by mains-related noise during daylight, with QRN rising during darkness. Actually, the mains noise level was lower than usual during this period, compared to that during last weekend's experiments.

The loop antenna orientation was the same E-W as used during reception of DK7FC - this means several of the utilities are significantly attenuated due to being away from the maximum directional response of the loop.

Cheers, Jim Moritz
73 de M0BMU

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