[Spooks] LORAN-A
Martin Potter
mpotter at storm.ca
Wed Sep 1 17:08:43 EDT 2004
As an aside (an off-topic one at that), the movie version of the
story "On the Beach" by Nevil Shute used LORAN-A signals to make
the sound of radio interference while the main characters were
trying to receive a mysterious Morse signal. The "beat note"
between two different trains of LORAN-A pulses, at different
pulse repetition frequencies, was unmistakable and commented on
at the time by many who knew what the signals sounded like.
LORAN-A operated on at least 1800, 1850, 1900, and 1950 kHz in
different chains around the world. If you could hear any LORAN-A
signals at all, you could almost always hear several different
chains at different PRFs, and could listen to the rising and
falling "beat note" between them (caused by the constantly
changing relative timing of the different pulses).
Ben, very glad to hear that LORAN-C isn't going to go away! At
one time there were plans to drop it in favour of GPS.
73,
... Martn VE3OAT
Ben Mesander wrote:
>
>>The rolling sound thing sounds like Loran. It was used by ships as a
>>navigational aid.
>>
>>30 years ago when I fist got on top band (160m) it was around 1950Khz, but
>>the Australian transmitter was in 1850 I think. Used to spread 40Khz. It was a
>>pain, and took up lage portion of the band.
>>It was phased out in the ealy 80's in favour of the Decca Navigation. That
>>went recently too, in favour of GPS.
>
>
> Loran-C is alive and kicking in many parts of the world on 100kHz. Loran is a loud clicky sound as it is a time domain multiplexed pulse modulation.
>
> I wrote the timescale firmware for the new Loran-C stations the USCG is deploying.
>
> Enjoy,
> Ben
>
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