Alan:
Yes I have spent some time at the Megapulse site, and that tells me all the
power levels, but I assume these are given as the peak pulse power. What I
need now is to convert these to mean power then I can calculate the mean
power per kHz and from there the mean power per spectral line. There is a
picture of a LORAN pulse wave on that site and I guess I could analyse it to
calculate the peak-to-mean ratio, but I am just hoping that someone out
there may have done it or knows where to find the answer.
Of course if we listen just to individual spectral lines then all the
transmitters in a chain will add (or subtract) and confuse the problem - I
already found this using my coherent weak-signal software - but as you say,
if one transmitter is clearly closer than all others in a chain, then it
should be possible to use it as a calibration point or at least as a quick
check to see if the equipment is working. For example, here in the UK I
guess most people will receive Rugby stronger than the others. I am also
simply curious to know what is the actual power level of these spurii. Is it
milliwatts or watts? How low are we going with our standard QRSS methods?
I have now extended the coherent software so I can receive the spurious
LORAN signals as pulses. This is about 25dB more sensitive that looking for
a single spectral line, because I am effectively adding-together ALL the
spurious spectral lines I can hear in the 3kHz SSB receiver. I can, for
example, copy the Slonim (Belarus) LORAN transmitter, 1800km away, at
midday, on 136.5kHz in a bandwidth of +/-1.5kHz. It's 20dB/noise, but of
course that is after 15 minutes of coherently summing the signal. The nice
thing about this technique is that the different transmitters in the chain
do NOT mix together. I can even read the 8-bit BPSK ident code inside each
pulse - the modulation on the spurious emissions is still perfectly
readable. Maybe I could even copy some of the USA LORAN transmitters on
136kHz using this idea. No more need for beacons, just record the dx LORAN
pulses!
Marco:
Thanks for the info about the Sellia Marina transmitter. Is this still
operating? I thought that the Mediterranean chain had closed down.
73
Peter G3PLX
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