Hello Geri
I made some laboratory tests this morning to get some indication about the
ability to communicate with signals below noise level using Slow-CW.
A most interesting set of measurements. Most of us who use this mode
felt that an it gave an extra 15 to 20dBs but this is the first time
I have seen objective measurements.
While not giving the same noise improvement described in the
pionering work of G3PLX and G4JNT described in the LF Experimenter's
Book, Spectrogram and Spectran does provide a convenient compromise
that can be managed by us non-techies.
I have made some improvements to the antenna and although this gives
me an extra 0.5Amps on transmit, the downside is that it has
increased the level of the Loran sidebands. While the strength of
each of these sidebands is not that high the effect of several
hundred of them in a passband of 2.7kHz holds the S-meter at S9!
While the fix would be to use a directional receiver antenna, such as
that used by Laurie or Derek, with QRSS it is not necessary because
of the ability of this mode to read signals between the Loran lines.
I would be interested to get your comments or own measurements on this
subject. I do not yet have sufficient experience with Spectran to make full
advantage of this software, so I would like to hear about that software as well.
During the month of tests receiving the 20mW erp from I5TGC over an
1800km path (plus Alps) I found Spectran had a slight advantage (even
at its Beta stage) mainly because it has a higher frequency
resolution. I used the 0.125Hz setting which placed the Loran
sidebands (on average) about 15mm apart, which gives plenty of space
to see a signal. The best compromise dot period for 0.125Hz apears to
be around 5 seconds.
At this stage the Speed Control (integration time?) is not slow
enough take advantage of the 0.064 and 0.032Hz settings of Spectran.
It would be interesting test these narrower settings to find the
limit of the soundcard.
Geri, I would be most interested in any tests you may make on
Spectran - I take it you have a copy.
--
Regards, Peter, G3LDO
<[email protected]>
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