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LF: PSK08 and Jims Vectorscope

To: [email protected]
Subject: LF: PSK08 and Jims Vectorscope
From: "Talbot Andrew" <[email protected]>
Date: Tue, 19 Feb 2002 09:55:23 -0000
Reply-to: [email protected]
Sender: <[email protected]>
Firstly, Jim, can you send me a copy of your vectorscope circuit please - it
may be a case of "Coals to Newcastle" but I'm intrigued !  Now, how about
the next version, a direct conversion receiver generating quadrature signals
at 137kHz then having masses of low frequency gain before the X/Y plot ?


Secondly, referring to Wolf's and others earlier postings.  I believe linear
modes such as PSK08 are probably of little value on this band for weak
signal working.  PSK31 (and hence ..08,   ..01 etc) have been heavily
optimised for bandwidth reduction at the expense of signalling efficiency,
and result in a minor degradation compared with harder switched PSK modes.
Where bit symbols approach one second, we need to decide if the key clicks
really are a problem - at 1 symbol per second I doubt very much anyone is
going to notice them.

For PSK31 itself, which is a lot faster and slightly better than 18WPM CW in
signalling performance, this argument probably is not true though.  As the
spectrum from overdriven transmitters often shows !

The complexities and inefficieny of using a linear Tx, just to keep the
bandwidth down for PSK08 and ..01 when hardly anyone one will notice is
mainly one of conscience I guess !

Andy  G4JNT

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