Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mh01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 2BF9238000192; Wed, 24 Aug 2011 12:27:44 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QwGI2-0006Oy-36 for rs_out_1@blacksheep.org; Wed, 24 Aug 2011 17:26:54 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QwGI1-0006Op-DS for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 17:26:53 +0100 Received: from out1.ip04ir2.opaltelecom.net ([62.24.128.240]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QwGHy-0003M7-Hs for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 17:26:53 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ArsAAH4lVU5cHnUG/2dsb2JhbABClBYDhAWPWHiBOQIFAQEFCAEBAzwNAhMZAQEDBQIBAxEEAQEKJRQBBAgSBhYIBhMKAQICAQGHYgK7IIZJBIJRhGGVXocF X-IronPort-AV: E=Sophos;i="4.68,275,1312153200"; d="scan'208,217";a="343593475" Received: from host-92-30-117-6.as13285.net (HELO xphd97xgq27nyf) ([92.30.117.6]) by out1.ip04ir2.opaltelecom.net with SMTP; 24 Aug 2011 17:26:43 +0100 Message-ID: <003e01cc627a$9bde96d0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: Date: Wed, 24 Aug 2011 17:26:42 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: WSPR or QRSS: which is better? Content-Type: multipart/alternative; boundary="----=_NextPart_000_003B_01CC6282.FD70F250" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE 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: 0:2:467712896:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d60d54e5526800e68 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_003B_01CC6282.FD70F250 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Like the man says either you get something or NOTHING which is often the = case, whereas with QRS you always get SOMETHING and since all radio = amateurs are competent with morse code and where there is fade or drop out you can fill the gaps, not the case with wspr = or the other data modes, and like I said already with poor un decodeable = wspr had the transmission been in QRS a messages could be exchanged. g3kev =20 ----- Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 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 = 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_003B_01CC6282.FD70F250 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Like the man says either you get something or = NOTHING=20 which is often the case, whereas with QRS you always get SOMETHING and = since all=20 radio amateurs are competent with morse code and where
 there is fade or drop out you can fill the = gaps, not=20 the case with wspr or the other data modes, and like I said already with = poor un=20 decodeable wspr had the transmission been in QRS a messages could be=20 exchanged.
g3kev
 
 
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Wednesday, August 24, = 2011 5:12=20 PM
Subject: Re: LF: WSPR or QRSS: = which is=20 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 -=20 12dB S/N for near error-free performance)
 
QRSS has to show about 6 - 10dB in its signal bandwidth to = be able=20 to discern fully what is sent, although a slightly lower S/N may be = useable=20 when 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=20 S/N 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 /=20 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=20 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=20 forces certain callsign and locator formatting.   So in all=20 probablility, more like 7 or 8 effective characters (I'm being a bit = empirical=20 here)
 
Assuming standard QRSS - not DFCW - , which if like standard = Morse, then=20 5 characters takes about 50 dot symbols to send (12WPM =3D 60 chars in = 1 minute,=20 =3D 1 char / second, or about 10 dot periods / = second.    Dot=20 speed =3D WPM / 1.2)   If we have 2s dots, that is 5 characters = can be=20 sent in 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=20 question for the coding experts here: WSPR is an excellent weak = signal=20 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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