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LF: Bandwidths/Modes

To: [email protected]
Subject: LF: Bandwidths/Modes
From: "James Moritz" <[email protected]>
Date: Wed, 11 Apr 2001 19:24:33 +0000
Organization: University of Hertfordshire
Reply-to: [email protected]
Sender: <[email protected]>
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




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