Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mc05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 96773380000D4; Wed, 24 Aug 2011 12:48:39 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QwGcN-0007CA-8r for rs_out_1@blacksheep.org; Wed, 24 Aug 2011 17:47:55 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QwGcM-0007Bu-91 for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 17:47:54 +0100 Received: from smtp5.freeserve.com ([193.252.22.151] helo=smtp6.freeserve.com) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QwGcJ-0003ot-NH for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 17:47:54 +0100 Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3509.me.freeserve.com (SMTP Server) with ESMTP id E223E70000A5 for ; Wed, 24 Aug 2011 18:47:45 +0200 (CEST) Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3509.me.freeserve.com (SMTP Server) with ESMTP id D64CA70000A7 for ; Wed, 24 Aug 2011 18:47:45 +0200 (CEST) Received: from AGB (unknown [2.26.17.7]) by mwinf3509.me.freeserve.com (SMTP Server) with SMTP id 62B6470000A5 for ; Wed, 24 Aug 2011 18:47:43 +0200 (CEST) X-ME-UUID: 20110824164743404.62B6470000A5@mwinf3509.me.freeserve.com Message-ID: <790E5582101F4A069156B4677843CD78@AGB> From: "Graham" To: References: In-Reply-To: Date: Wed, 24 Aug 2011 17:47:42 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 X-Antivirus: avast! (VPS 110824-1, 24/08/2011), Outbound message X-Antivirus-Status: Clean X-Spam-Score: 0.2 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RCVD_ILLEGAL_IP=0.234 Subject: Re: LF: WSPR or QRSS: which is better? Content-Type: multipart/alternative; boundary="----=_NextPart_000_0092_01CC6285.EC9CC050" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_20_30, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE,MISSING_OUTLOOK_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:449093088:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d604d4e552b66457c X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_0092_01CC6285.EC9CC050 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable >> and gives absolutely guaranteed error free decoding, or nothing at = all. << Are you sure ?=20 G.. From: Andy Talbot=20 Sent: Wednesday, August 24, 2011 5:12 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: WSPR or QRSS: which is better? WSPR works in a 1.46Hz signal bandwidth and because of its very high = level of error correction and soft-decision decoding, means that it will = work at a S/N of about 3dB in this bandwidth, and sometimes a bit lower = still (Normally, FSK with no correction at all needs about 10 - 12dB = S/N for near error-free performance) QRSS has to show about 6 - 10dB in its signal bandwidth to be able to = discern fully what is sent, although a slightly lower S/N may be useable = when you 'know' what you should be receiving. (A form of forward error = correction is now in use here as well perhaps :-) So lets say 5dB S/N = is a working value.. So take 3dB in 1.46Hz as a starting point and derive the bandwidth for = QRSS needed to get 5dB S/N with the same signal. This will have to be = narrower to get a 2dB higher S/N and works out as 1.46 / 10^(2/10) =3D = 0.92Hz So QRSS used with a 0.9Hz bandwidth - which I think means about a 2 - 3s = dot period ought to be decoded at the same S/N as a WSPR signal. Which = is probably the info you wanted. But now compare source coding efficiencies. WSPR fits a callsign, = locator and power level into a 110 second transmission - and gives = absolutely guaranteed error free decoding, or nothing at all. About 12 = characters in actuality, but that is being a bit unfair as the coding = forces certain callsign and locator formatting. So in all = probablility, more like 7 or 8 effective characters (I'm being a bit = empirical here) Assuming standard QRSS - not DFCW - , which if like standard Morse, then = 5 characters takes about 50 dot symbols to send (12WPM =3D 60 chars in 1 = minute, =3D 1 char / second, or about 10 dot periods / second. Dot = speed =3D WPM / 1.2) If we have 2s dots, that is 5 characters can be = sent in the time for a WSPR transmission. So as a quick estimate, WSPR wins by roughly 2dB in S/N terms for a = given dot period / noise bandwidth. And at similar S/N values, WSPR is = about 1.5 times faster Andy www.g4jnt.com On 24 August 2011 16:42, Roger Lapthorn wrote: A question for the coding experts here: WSPR is an excellent weak = signal beaconing mode, but at what QRSS speed is QRSS "better" ? 73s Roger G3XBM --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm https://sites.google.com/site/sub9khz/ ------=_NextPart_000_0092_01CC6285.EC9CC050 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
>>  and gives absolutely guaranteed error free decoding, = or=20 nothing at all.  <<
 
Are you sure ? 
 
G..

Sent: Wednesday, August 24, 2011 5:12 PM
Subject: Re: LF: WSPR or QRSS: which is = better?

WSPR works in a 1.46Hz signal bandwidth and because of its = very high=20 level of error correction and soft-decision decoding, means that it = will=20 work at a S/N of about 3dB in this bandwidth, and sometimes a bit lower=20 still  (Normally, FSK with no correction at all needs about 10 = - 12dB=20 S/N for near error-free performance)
 
QRSS has to show about 6 - 10dB in its signal bandwidth to be = able to=20 discern fully what is sent, although a slightly lower S/N may be useable = when=20 you 'know' what you should be receiving.  (A form of forward error=20 correction is now in use here as well perhaps :-)  So lets say = 5dB S/N=20 is a working value..
 
So take 3dB in 1.46Hz as a starting point and derive the=20 bandwidth for QRSS needed to get 5dB S/N with the same signal.  = This will=20 have to be narrower to get a 2dB higher S/N and works out as 1.46 / = 10^(2/10) =3D 0.92Hz
 
So QRSS used with a 0.9Hz bandwidth - which I think means about a 2 = - 3s=20 dot period ought to be decoded at the same S/N as a WSPR = signal.  =20 Which is probably the info you wanted.
 
But now compare source coding efficiencies.   WSPR fits a = callsign, locator and power level into a 110 second transmission - and = gives=20 absolutely guaranteed error free decoding, or nothing at = all.  About=20 12 characters in actuality, but that is being a bit unfair as the coding = forces=20 certain callsign and locator formatting.   So in all = probablility,=20 more like 7 or 8 effective characters (I'm being a bit empirical = here)
 
Assuming standard QRSS - not DFCW - , which if like standard Morse, = then 5=20 characters takes about 50 dot symbols to send (12WPM =3D 60 chars in 1 = minute, =3D 1=20 char / second, or about 10 dot periods / second.    Dot = speed =3D=20 WPM / 1.2)   If we have 2s dots, that is 5 characters can be = sent in=20 the time for a WSPR transmission.
 
So as a quick estimate, WSPR wins by roughly 2dB in S/N terms = for a=20 given dot period / noise bandwidth.  And at similar S/N values, = WSPR is=20 about 1.5 times faster
Andy
 
 
 
 
On 24 August 2011 16:42, Roger Lapthorn <rogerlapthorn@gmail.com>=20 wrote:
A question for the coding experts here: WSPR is an = excellent=20 weak signal beaconing mode, but at what QRSS speed is QRSS "better"=20 ?

73s
Roger G3XBM

--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/

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