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Dear Laurence,
good to read you're back in AK...
Your observation is interesting. In your region,
there should now be two chains left on air. One is the Canadian
West Coast chain on GRI 5990, which is still supported by US
stations, including your nearest one Shoal Cove (5990 X). The other is
the Russian-American GRI 5980, which should be supported by Attu
(5980 W). The slow phasing effect is caused by pulsegroups of
these very similar rates, walking through one another in time.
The attached screenshots are the results of feeding
your wav to SpecLab's time domain scope. Using 64 averages on 5990,
AM-demodulated pulsegroups from all stations from the West Canadian chain are
visible. The timescale appears a bit too long because the actual
samplerate was close to 22.200 kHz, rather than 22.050 as assumed
by SpecLab. When going to 5980, we can see only a single group of 6 pulses.
This is an unusual format for Loran-C, probably indicating an error condition by
"blinking" the first two of the eight pulses. One possible reason for this
might be the Russian master being down.
It would be interesting to look at an SSB recording
(eg. 98.25 kHz USB). This could reveal phase coding within the
pulsegroups, and possibly allow verification of the blinking
secondary.
Best 73,
Markus (DF6NM)
Sent: Friday, February 19, 2010 4:42 AM
Subject: LF: Loran A and C
Being of a certain age I oft recall
the musical phasing noises of Loran on 160m and kind of missed the musical
sounds they made as sky waves did their thing. With the advent of the closedown
of most of the American 100 khz chains save those serving Canadian and Russian
chains I took a listen from here on my newly erected larger (maybe 75m) permeter
E/W LF loop and phased out one signal and was left with a slowly phasing noise
very similar to that heard on 160m - I dont recall hearing it before but of
course a lot of the chains/half rate are off so.... Now whether this
is just due to the rather unstable conditions today up here - a lot of iono
smearing seen on HF but anyway heres the link of what it sounded like from here
in Wasilla AK = Its a 2Mb file beware best phase noise towards the
end...
Laurence KL1X "Palinville" Wasilla Alaska BP51 Eye
Pee
We2 XP Q
http://kl1x.com/loranalaska.wav
ps
the large loop is to improve my s/n on 137 and 500 and it seems pretty good -
Ive also been running a CW beacon around 506.000 Khz this evening but low
power as Im playing with the matching -
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