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Re: LF: All 73 Banders...

To: [email protected]
Subject: Re: LF: All 73 Banders...
From: Hartmut Wolff <[email protected]>
Date: Sat, 14 Dec 2013 16:49:35 +0100
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Here is a screenshot how 72.7 dial here looks.

http://dl.dropboxusercontent.com/u/26404526/Eu_Loran_frequencies_74300-74325Hz.txt

74321 is better than 74304, but not optimal because the Loran line on 74320.3 is to close I think.

--
73
Hartmut


Am 2013-12-14 16:03, schrieb Markus Vester:
Hmmm - capturing Bob's WSPR is a bit like crossing a four lane highway by foot: 
Once you've managed to find a gap between the DCF trails, you'll be hit by a 
Loran line on the next track...

Glad to see that Joe DF2JP managed to get some decodes, probably for the first time. His 
capture shows significant DCF77 "junk", the effect of which we have apparently 
reduced successfully.

Around midnight there were also some meager traces here, but simply not enough 
SNR to decode. I have marked the four tones with 0.1831 Hz spacing with green 
arrow heads on
  
http://dl.dropboxusercontent.com/u/26404526/df6nm_74kHz_131214_0200_arrowheads.png
Unfortunately 74612 Hz would not be good here.

It's however strange that Hartmut and Victor didn't get any decodes, even 
though the signal seemed to be well visible for both. What looks like noise on 
Victor's capture must really be the WSPR-15 spectrum:
  
http://dl.dropboxusercontent.com/u/26404526/pa3fny_74603_131214_0700_arrowheads.jpg

But both statiopns have a relatively strong Loran line, and Hartmut's 
directional antenna is pointing towards Sylt. However the nearby line frequency 
74603.280 Hz should have been well outside the occupied spectrum of Bob's WSPR 
signal (74603.51 to 604.24), so it's not ovbvious why it should have prevented 
decodes. I'm speculating that the WSPR software finds the strong line, tries to 
sync to it, and then somehow excludes nearby real signals from further decode 
attempts. To prove the point and see how much spacing is needed, we could 
experiment with letting WSPR decode local audio signals in the presence of 
injected carriers. But systematic trials with WSPR tend to be time-consuming, 
even if such tests were accelerated by scaling to WSPR-2.

As Bob says, the best solution would be to move further out, avoiding the DCF77 
sideband lobes alltogether:
  
http://dl.dropboxusercontent.com/u/26404526/74kHz_spectrum_investigation_df6nm_131214.png
shows different parts of the spectrum in detail. My idea would be to move down 
by 300 Hz, ie 72.7 kHz dial and 74.300 to 74.325 kHz RF for WSPR-15. In that 
range, DCF noise is so weak that we would only neeed to avoid the more widely 
spaced Loran lines. I have listed and sorted the relevant GRI harmonics at
  
http://dl.dropboxusercontent.com/u/26404526/Eu_Loran_frequencies_74300-74325Hz.png
  
http://dl.dropboxusercontent.com/u/26404526/Eu_Loran_frequencies_74300-74325Hz.txt
but note that emitted levels are variable, and not every line will really be 
strong enough to cause interference.

Thus my suggestion would be to go to 72.7 kHz dial, and Bob sending on either 
74304 or 74321 Hz.

Best 73,
Markus (DF6NM)




From: Bob Raide
Sent: Saturday, December 14, 2013 8:41 AM
To: [email protected] ; Bob Raide
Subject: LF: All 73 Banders...


I am authorized 68-76 kHz.  There must be clear freqs somewhere in that 
spectrum?  Let me know what most would like to try in UK/Europe-Bob WG2XRS/4 NY 
[WG4XRS for WSPR modes]



--
73
Hartmut
www.h-wolff.de
Locator: JO52hp


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