From: MarkusVester@aol.com
Message-ID: <122.9e3b3cb.29606ae7@aol.com>
Date: Sun, 30 Dec 2001 08:04:39 EST
Subject: LF: Band full ?
To: rsgb_lf_group@blacksheep.org
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Hi transatlantic gang,

Band full? No, I believe there is plenty of space, it's just that we may have 
to move a little closer: QRSS or DFCW watched with 10 mHz resolution could 
leasurely be spaced at 100 mHz intervals. As the level differences between 
different Eu sigs seen in America will hardly exceed 15 dB, spectral widening 
during the keying is not a problem. Propagational doppler spread should also 
be less than 10mHz (though there has been one unexplained observation of wide 
doppler on a ZL-P29 LF path, not sure whether this was real).

So it all becomes only a question of frequency accuracy and stability. Some 
stations (e.g. BMU, FTC, YXM and hopefully myself) are within 10mHz of stated 
freq (10^-7), which requires a calibrated OCXO or a very good TCXO. All 
others I have seen lately apparently use standard <1ppm crystal oscillators 
and have drifted less than 50mHz, which still is good enough. Only those rigs 
generating LF by mixing two independent HF xtals are probably not stable 
enough for real narrowband work.

7fsk must be regarded as a special case. In my opinion, much narrower tone 
spacings (20 to 50 mHz) should be preferred, and could even improve 
legibility because the sequence can be connected visually much easier. 

Though I don't particularly favor the thought of "frequency ownership" (still 
the anarchist in me, at age 43?), I agree that allocations will make life 
easier, and the receiving side can associate T-grade traces to their owners.

So some 30 stations could work in a 60s-Argo slot in parallel. (Btw I do 
prefer the "90s slow" setting with equal frequency resolution.Temporal 
resolution is anyhow limited by FFT bandwidth, the slower display simply 
saves screen space.) And if that were not enough, we might eventually have to 
ask Alberto for a higher window.

73 es have a nice sunny sunday
de Markus, DF6NM