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LF: LF mysteries: "s" on 137.722, pips on 71.7

To: [email protected]
Subject: LF: LF mysteries: "s" on 137.722, pips on 71.7
From: [email protected]
Date: Sun, 10 Dec 2000 10:54:21 EST
Reply-to: [email protected]
Sender: <[email protected]>
Hello group,

for the last couple of weeks I observed a funny signal on 137.22 kHz, sending a sequence of 16 Morse "s" characters. Timing is 250 ms dotlength (4 wpm), 2 s per letter and 32 s total. The sequence repeats at irregular intervals, typically less then 10 minutes in between. Keying seems to be phase-coherent, in high-res spectrograms there appears a set of washed-out lines, spaced 2 Hz apart. Field strength is fairly constant at 7 dBuV/m, well audible above the noise. Wonder if someone else has noticed it, or can explain it.
On Dec. 5th, Jim mentioned short "pips" on 71.7 kHz. I remember hearing these
clearly with Jims signal last weekend, on 71.7 and also on a second QRG
somewhere below the band. This weekend they seem to have disappeared. To
confirm, I had a look at spectrograms recorded 3rd of March this year, and
sure enough they were there, above the DECCA dashes. Different dots in the
sequence indeed did have different amplitudes and slightly different freqs
(20 Hz). I had always assumed they were part of the DECCA system, perhaps
someone had forgotten to switch them off...
Best wishes to all
Markus, DF6NM

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