Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk04.r1000.mx.aol.com (Internet Inbound) with ESMTP id C82B9380000AB; Wed, 24 Aug 2011 12:13:46 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QwG4W-00068Y-EK for rs_out_1@blacksheep.org; Wed, 24 Aug 2011 17:12:56 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QwG4V-00068P-Tv for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 17:12:55 +0100 Received: from mail-iy0-f173.google.com ([209.85.210.173]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QwG4S-00031k-Iz for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 17:12:55 +0100 Received: by iyk2 with SMTP id 2so2521099iyk.4 for ; Wed, 24 Aug 2011 09:12:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=+jvpH3ShVmKxp80foaqYw+l2mFt+4Q+keE1vblHRZhQ=; b=kvtPJOJ0gtSyz+lc4ChQHh68qE/GvOV+a27ylRkbVSxdR/rBNhRqu+miypwpL5ZOiH 9TA9j/E9Th9yRc/69tlc0ZtDPQf4wJvX8tHRt+SObO2YGwJ4DbpBo0cDX7N5kanBeZ5r cXnKs/dEFNP6AKNn40LhCOkJE1MfllhXYE+3g= MIME-Version: 1.0 Received: by 10.231.67.80 with SMTP id q16mr10390915ibi.86.1314202365095; Wed, 24 Aug 2011 09:12:45 -0700 (PDT) Received: by 10.231.43.136 with HTTP; Wed, 24 Aug 2011 09:12:45 -0700 (PDT) In-Reply-To: References: Date: Wed, 24 Aug 2011 17:12:45 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org 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=0015176f09c8226e9104ab4295e0 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=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: 0:2:414147168:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d306.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1db4084e55233a7950 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --0015176f09c8226e9104ab4295e0 Content-Type: text/plain; charset=ISO-8859-1 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) = 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 = 60 chars in 1 minute, = 1 char / second, or about 10 dot periods / second. Dot speed = 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 > > -- > http://g3xbm-qrp.blogspot.com/ > http://www.g3xbm.co.uk > http://www.youtube.com/user/g3xbm > https://sites.google.com/site/sub9khz/ > > --0015176f09c8226e9104ab4295e0 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
WSPR works=A0in a 1.46Hz signal bandwidth and because of its very high= level of error correction and soft-decision decoding, means that=A0it will= work at a S/N of about 3dB in this bandwidth, and sometimes a bit lower st= ill=A0 (Normally, FSK with no correction at all=A0needs about 10 - 12dB S/N= for near error-free performance)
=A0
QRSS=A0has to show about 6 - 10dB in its signal bandwidth to be able t= o discern fully what is sent, although a slightly lower S/N may be useable = when you 'know' what you should be receiving.=A0 (A form of forward= error correction is now in use here as well perhaps=A0:-)=A0 So lets say 5= dB S/N is a working value..
=A0
So take=A03dB in 1.46Hz=A0as a starting point and derive the bandwidth= for QRSS needed to get 5dB S/N with the same signal.=A0 This will have to = be narrower to get a 2dB higher S/N and works out as 1.46=A0/ 10^(2/10) =3D= 0.92Hz
=A0
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.=A0=A0 W= hich is probably the info you wanted.
=A0
But now compare source coding efficiencies.=A0=A0 WSPR fits a callsign= , locator and power level into a 110 second transmission - and gives absolu= tely guaranteed error free decoding, or nothing at all.=A0=A0About 12 chara= cters in actuality, but that is being a bit unfair as the coding forces cer= tain callsign and locator formatting.=A0=A0 So in all probablility, more li= ke 7 or 8 effective characters (I'm being a bit empirical here)
=A0
Assuming standard QRSS - not DFCW - , which if like standard Morse, th= en 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.=A0=A0=A0 Do= t speed =3D WPM / 1.2) =A0 If we have 2s dots, that is 5 characters can be = sent=A0in the time for a WSPR transmission.
=A0
So as a quick estimate, WSPR wins by=A0roughly 2dB in S/N terms for a = given dot period / noise bandwidth.=A0 And at similar S/N values, WSPR is a= bout 1.5 times faster
Andy
=A0
=A0
=A0
=A0
On 24 August 2011 16:42, Roger Lapthorn <rogerlapthorn@gmai= l.com> wrote:
A question for the coding expert= s here: WSPR is an excellent weak signal beaconing mode, but at what QRSS s= peed is QRSS "better" ?

73s
Roger G3XBM

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

<= /font>

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