Message-ID: <2565.200104111824@gemini>
From: "James Moritz" <j.r.moritz@herts.ac.uk>
Organization: University of Hertfordshire
To: rsgb_lf_group@blacksheep.org
Date: Wed, 11 Apr 2001 19:24:33 +0000
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Subject: LF: Bandwidths/Modes
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Dear LF Group,

Regarding the bandwidth occupied by BPSK - John, KD4IDY has 
kindly posted the spectra I obtained recently for various types of 
BPSK and phase modulation on the LWCA web site at 
http://lwca.org/miscimg/phasespectra.jpg. The top 3 spectra in the 
left hand column are relevant to the current discussion, showing 
"raw" and envelope-shaped BPSK sigs, with 12wpm CW for 
comparison. The vertical scale is 10dB/div, the horizontal span 
400Hz. It is clearly true that the "raw" signal is undesirably wide, 
but the fully-engineered signal fits into a sensible bandwidth, which 
is why I went to all that trouble!

I agree that the bandwidth  occupied by the current "Wolf" mode 
signals would become a problem if more than a handful of people 
tried to use the mode with the current band-plan. However, this 
mode is in the experimental stage at the moment, so that could 
change, and the "digital" band segment is not exactly busy at the 
moment. The main point of doing it is to try a different technique for 
improving detection of weak signals. There seems to have been 
few attempts by amateurs to utilise sophisticated coding 
techniques in this way. It is pretty clear that with the longer dot 
periods, the slow speed of QRSS is a real obstacle to 2 way 
communications, and so anything that improves on this is worth 
considering. The results achieved so far seem encouraging.

Cheers, Jim Moritz
73 de M0BMU