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Date: Tue, 16 Mar 2010 20:30:43 +0000
Message-ID: <fc7eccec1003161330k2c6da253ue3f6dac2c93d4f1@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: DK7FC's 2nd VLF TX test...
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If you go the the extent of UT synced FSK, then you'll gain another 3dB by
using BPSK.   FSK is an orthogonal signalling mode, where you test the power
level in one slot (frequency bin) against that in the other slot.   When
correlated over a symbol period, the resule will be either 1 for teh correct
tone, or 0 for th eotehr tone    However, BPSK compares the voltage
amplitude between the two states, so you're now testing for what amounts to
1 or -1.    Hence 3dB advantage for synchronous BPSK versus synchronous
FSK.

Normally you don't see the benefit in simple amateur signalling protocols
 as the need for carrier and bit timing recovery degrade the process, so for
casual signalling FSK wins - hence the power  of K1JT's JTxx and WSPR modes.

But, by introducing GPS locked and timed signalling, operating both ends
coherently, the latter issues go away and you should be able to get the full
theoretical advantage of synchronous signalling.


Andy
www.g4jnt.com

 Thanks for the info on the DDS VFO, now I recall you mentioned
> it in an earlier post.   I wondered whether it would do FSK.
> The QRSS mode is very poor, a most inefficient use of the
> channel capacity - literally a waste of time.  Dual frequency
> Morse code would be much better, but better still an efficiently
> encoded digital signal sent with UT synchronous FSK.
>
> Probably Spectrum Lab already has everything you need for
> this, including the ability to sync the carrier frequency to
> an external frequency standard.
>
> > i plan to get the permission for a 300m vertical antenna!
>

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<div>If you go the the extent of UT synced FSK, then you&#39;ll gain anoth=
er 3dB by using BPSK.=A0=A0 FSK is an orthogonal signalling mode, where yo=
u test the power level in one slot (frequency bin) against that in the=A0o=
ther slot.=A0=A0=A0When correlated over a symbol period, the resule will=
 be either 1 for teh correct tone, or 0 for th eotehr tone=A0=A0=A0 Howeve=
r, BPSK compares the voltage amplitude between the two states, so you&#39;=
re now testing for what amounts to 1 or -1.=A0=A0=A0 Hence 3dB advantage=
 for synchronous BPSK versus synchronous FSK.=A0=A0 </div>

<div>=A0</div>
<div>Normally you don&#39;t=A0see the benefit in simple amateur signalling=
 protocols =A0as the need for carrier and bit timing recovery degrade the=
 process, so for casual signalling FSK wins - hence the power=A0 of K1JT&#=
39;s JTxx and WSPR modes.</div>

<div>=A0</div>
<div>But, by introducing GPS locked and timed signalling, operating both=
 ends coherently, the latter issues go away and you should be able to get=
 the full theoretical advantage of synchronous signalling.</div>
<div>=A0</div>
<div><br clear=3D"all">Andy<br><a href=3D"http://www.g4jnt.com">www.g4jnt.=
com</a><br><br></div>
<div class=3D"gmail_quote">
<blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8e=
x; PADDING-LEFT: 1ex" class=3D"gmail_quote">Thanks for the info on the DDS=
 VFO, now I recall you mentioned<br>it in an earlier post. =A0 I wondered=
 whether it would do FSK.<br>
The QRSS mode is very poor, a most inefficient use of the<br>channel capac=
ity - literally a waste of time. =A0Dual frequency<br>Morse code would be=
 much better, but better still an efficiently<br>encoded digital signal se=
nt with UT synchronous FSK.<br>
<br>Probably Spectrum Lab already has everything you need for<br>this, inc=
luding the ability to sync the carrier frequency to<br>an external frequen=
cy standard.<br><br>&gt; i plan to get the permission for a 300m vertical=
 antenna!<br>
</blockquote></div>

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