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Re: LF: ZL DX testing 21 September

To: [email protected]
Subject: Re: LF: ZL DX testing 21 September
From: "James Moritz" <[email protected]>
Date: Fri, 10 Aug 2001 12:45:28 +0000
Organization: University of Hertfordshire
Reply-to: [email protected]
Sender: <[email protected]>
Dear Bob, John, LF group,

I heard the Russian station on 171kHz for the first time last night - it shut down at 2000 utc as John says, but was only audible from 1900 at my QTH, which might have been due to propagation, or then again, it may just have been on the air for an hour. I have not heard it before when monitoring this frequency, so it may have very limited operating times. After it had closed down, another station was audible on the same frequency, with what sounded like Arabic music playing, but this was considerably weaker than the Russian station. Looking at a spectrogram display at frequencies close to 172kHz, the effect of this QRM was not unlike the "Luxembourg effect" noises often heard at the top end of 136k. The net effect was to raise the noise floor by a few dB, although QRN was still the main source of noise.
Of course, one way to improve the situation would be to null out
the offending noise with a loop - if the wanted signal from ZL
comes over the pole, and the unwanted signals originate in Russia,
this should work fairly well - does anyone know what bearing a
signal from ZL should arrive on?
It seems strange the LF spectrum does not get used much "down
under" - I would have thought it would work very well with all that
ocean to propagate over.
DBF 39 transmits a carrier on 138.83kHz most of the time,
interspersed at intervals of several seconds with short bursts of
FSK data, mark 138.83kHz, space 139.17kHz. On a spectrogram,
it will look like a 138.83kHz carrier unless a very coarse resolution
is used.
Cheers, Jim  Moritz
73 de M0BMU

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