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References: <20091226.144128.11516.4.cw4ever4@juno.com>
	 <469B391A02A04C259832ED9427C8E689@AGB>
Date: Sat, 26 Dec 2009 20:51:29 +0000
Message-ID: <fc7eccec0912261251na0b0eb0n4c9693a0bb4de629@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
DomainKey-Status: good (testing) 
Subject: Re: LF: "WA" beacon & WSPR 2.0
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You might like to try the JT4A mode available within the WSJT suite.
The latest Ver 7.4 has improved JT4 decoding,  and we've been using
the wide shift JT4G version on the microwave bands over the last year.

JT4A is also a four tone MFSK signal, but at a tone spacing / baud
rate of 4.375 Hz with a complete transmission taking 48 seconds.  It
uses the same convolutional coder, interleaving and 50% embedded sync
techniqe as WSPR, but the message contents are different.  They can
consist of two callsigns and a locator, 2 * call + report, or 13
digits of plain text (we use the latter on microwaves as beacon
identifiers)

So JT4A has almost exactly three times the bandwidth of WSPR, and with
identical FEC the resulting sensitivity 'ought' to be about 5dB worse,
but the faster message time may have the advantage.

There is one pratical matter you need to watch out for.   WSPR uses a
11025Hz sampling rate, and as we've all discovered this value is often
out on later PCs, and can destroy decoding even of strong signals (see
December's RadCom).   WSJT.EXE does have its own calibration facility
built in and sampling rate errors can be corrected in the setup .

Andy
www.g4jnt.com

This email has been scanned for damaging side-effects by the health
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2009/12/26 Graham <g8fzk@g8fzk.fsnet.co.uk>:
> Ok Bob
>
> >
> I would think (based on past experience) that =A0it =A0would of =A0been=
 =A0better to
> go the =A0other =A0way =A0with a shorter tx pulse containing =A0all the=
 =A0data as the
> 30 =A0second =A0in and =A0120 second =A0out =A0qsb times are not idea fo=
r =A0wspr at the
> best of =A0times ?
>