Re: Microhertzing at LF:

["Markus Vester" <markusvester@aol.com>]

Hi Chris,

 

yes, there were good and narrow traces on both grabbers throughout the dark period, confirming the stability of a long skywave path. In Haifa, the upward Doppler shift around sunrise was clearly visible.

 

Going by your very useful DCF / HGA plots, there is a day-night difference of about 30 dB on the DL to 4X path, and 20 dB for YO. I have left the carrier on to see whether anything would come through in daylight, but nothing above the noise so far.

 

Thanks very much for offering the chance for this interesting experiment!

 

Best wishes,

Markus  (DF6NM)

From: Chris 4X1RF

Sent: Friday, September 02, 2011 11:38 AM

To: rsgb_lf_group@blacksheep.org

Subject: Re: Microhertzing at LF:

Markus, LF,

Your night long transmission appeared nicely in Haifa http://dl.dropbox.com/u/10280270/4x1rf_DF6NM_QRSS3600_2sept2011.jpg
and Bucharest http://dl.dropbox.com/u/10280270/YO/yo4x1rf_DF6NM_QRSS3600_2sept2011.jpg

There's room left for using much less power. Based on last night results, a 1mW EMRP from you should be about the same level as the 137780.29445 Loran trace in Haifa. It was a good opportunity to test both receivers, looking forward to further tests.


73s
Chris 4X1RF

On Fri, Sep 2, 2011 at 1:24 AM, Markus Vester <markusvester@aol.com> wrote:

trying again...

From: Markus Vester

Sent: Thursday, September 01, 2011 10:47 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: Microhertzing at LF:

Hi Chris,

 

thanks for this! The Saudi Loran traces (GRI 8830) look very accurate on your 4X grabber. I will try to appear there tonight, and have started to send a straight carrier on 137780.30. TX power is now reduced to about 100 mW EMRP.

 

Best 73,

Markus

From: Chris 4X1RF

Sent: Thursday, September 01, 2011 1:34 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: Microhertzing at LF:

Markus, LF,

As a newcomer to LF I find this as an interesting experiment for real low power or long distance tests for those who can achieve the necessary frequency stability requirements. I found this to be quite a challenge...

I have followed your initiative and started similar windows on my grabbers in YO: http://dl.dropbox.com/u/10280270/YO/TA3600.jpg and 4X: http://dl.dropbox.com/u/10280270/4X/TA3600.jpg

The 4X grabber is currently using the Mercury HPSDR receiver (http://openhpsdr.org) which is GPSDO locked. However, the audio is routed to SpectrumLab using Virtual Audio Cable as a virtual sound card. I have no info regarding VAC sample rate accuracy or how I can automatically adjust it so this may be a limiting factor, further experimentation is needed. In the worst case, a real sound card could be used but then it also has to be locked to GPS.

The YO grabber is usually using GQD as a reference for the sound card sample rate calibration in SpectrumLab and the LF receiver is based on a laboratory grade VTCXO. GQD being off air, I was forced to use DHO which is not very reliable during the night for me as can be seen on the 137.775 Loran line.

Thanks for the challenge!


73s
Chris 4X1RF

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