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Thanks to Jay and Chris for this second experiment, and congratulations to both!
The XNS carrier was visible in Nuernberg approximately from 23:45-1:30, and again from 3:00-5:00. The higher frequency and directional error near the end might have been due to sunrise approaching. Like before, there was the gap in the middle, but this time without a distinctive Doppler-shifted dot.
Chris' 4X screenshot shows one continuous reception from about 0:30-2:30 in Haifa. As this extends well into my gap, the hypothesis of a midpath midnight minimum is certainly not generally valid.
Last not least, from 23:30 on the carrier was also discernible on the F1AFJ grabber, running at 33 mHz/pixel resolution. This demonstrates the clear advantage of Jean-Pierres location and directional antenna - at comparable bandwidth, he typically sees TA signals around 10 dB better than I do.
To better understand seasonal variations of the propagation patterns, we could repeat such tests on a regular (eg. monthly) basis. Of course it would also be valuable if more stations would participate, both on the transmit and receive side. The effort of generating stable signals will certainly be rewarded by the prospect of long distance and/or low-power detections.
Best wishes,
Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von: Chris 4X1RF < [email protected]>
An: rsgb_lf_group < [email protected]>
Verschickt: Mo, 5 Sept 2011 11:13 am
Betreff: Re: LF: Weak signal on 137780.3
Jay, Markus,
Nice trace on 780.31 in Haifa last night. There's a frequency locking problem on my Bucharest LF receiver which makes it unsuitable as it is now for this kind of work.
Thanks for the effort!
73s
Chris 4X1RF
On Sun, Sep 4, 2011 at 8:00 PM, Markus Vester <[email protected]> wrote:
Ok, Jay. The effect is intruiging. The Russian line on 775 tells me that the receiver had stayed in lock all night, so it must be real.
Yes it would be good to try the same parameters again. There's a lot of QRN now, but the forecast says it should quiet down later tonight.
I'm not hooked to 780.30, just left the slot where it was after I transmitted near Chris' Loran line in Haifa. So in case we would really cause a problem for Mitch we might as well move down a tick, even a posteriori as long as it's between 774 and 781. I think Chris could do the same both in 4X and YO if required.
Actually after John's email I tried to look for a trace of VE3OT as well. There were some bits below the Eu Loran line 780.419, but nothing conclusive. Do you happen to know his precise QRG?
Best 73, and have a nice Sunday
Markus (DF6NM)
Sent: Sunday, September 04, 2011 6:08 PM
Subject: Re: LF: Weak signal on 137780.3
Markus
Yes ... it was a continuous transmission with no frequency step. Interesting observation on midnight crossing the middle of the path.
Picked 200 watts as a starting point to see how well it was received. The transmitter here is capable of 1 kW output. It appears that only your grabber was able to 'see' the signal.
Weather permitting, I can run further tests tonight. Do you have anything in mind? Might be interesting to do a repeat of last night's test to see if the midnight/midpoint anomoly shows up.
Jay W1VD WD2XNS WE2XGR/2
----- Original Message -----
Sent: Sunday, September 04, 2011 9:56 AM
Subject: Re: LF: Weak signal on 137780.3
Excellent Jay, thanks very much! I am really happy about this result. Attached is a spectrum graph, showing your peak at 3:16 UT, with about 12 to 14 dB SNR in the 0.438 mHz FFT.
Do I understand you correctly in that you transmitted a continuous carrier, without a frequency step? Then the apparent 3.8 mHz shift must have been a transient propagational Doppler effect. Remarkably, this lines up with observations of John Andrew's tests in 2006, which had also shown two long stable runs, with a dip and rapid phase change inbetween. The dip seems to roughly coincide with midnight crossing over the middle of the path, but I'm not aware of any simple physical explanation for this.
BTW Your transmit situation must be similar to mine: I have about 200 W available into a Marconi antenna, which is about 0.1 percent efficient now, and up to twice that in a cold winter night.
Best regards, and thanks again for the test
Markus (DF6NM)
Sent: Sunday, September 04, 2011 1:27 PM
Subject: Re: LF: Weak signal on 137780.3
Markus
The mystery signal was from WD2XNS ... you have the time and frequency perfectly correct and the color DF also provides corroborating evidence. Note that there was no break in the transmission. The frequency is controlled by a GPS disciplined oscillator (accuracy about 13 ppt). Transmitter power was 200 watts ... radiated power is not known. During winter, with frozen ground, additional radials, lower R and less foliage, the radiated power would have been about 0.5 watt. Expect last night's test would be at least 3 - 6 dB (maybe more) below that level.
Jay W1VD WD2XNS WE2XGR/2
----- Original Message -----
Sent: Sunday, September 04, 2011 4:45 AM
Subject: Re: LF: Weak signal on 137780.3
The mystery signal was received between about 0:15 and 3:30 on 137780.310, with a 3.8 mHz downward shift from about 1:30 to 2:15 - somewhat reminiscent of a DFCW "GM". Greenish colour indicates southwesterly origin. The attached screenshot was taken at 8 UT, timescale is 10 minutes per FFT.
I checked the other available TA grabbers around 4 UT, but no trace of the mystery signal.
73, and have a nice sunday,
Markus (DF6NM)
Sent: Sunday, September 04, 2011 5:39 AM
Subject: LF: Weak signal on 137780.3
LF,
there seems to be a signal on 137780.300 Hz, about 60 nV/m here.
Wondering whose it may be...
Best wishes,
Markus
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