Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc03.r1000.mx.aol.com (Internet Inbound) with ESMTP id D6BC738000102; Wed, 24 Aug 2011 13:07:56 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QwGur-0007ne-3K for rs_out_1@blacksheep.org; Wed, 24 Aug 2011 18:07:01 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QwGuq-0007nV-Gs for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 18:07:00 +0100 Received: from mail-gx0-f171.google.com ([209.85.161.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QwGun-0004PA-US for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 18:07:00 +0100 Received: by gxk22 with SMTP id 22so1421381gxk.16 for ; Wed, 24 Aug 2011 10:06:51 -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=ear3eon5qI+WDR1QyCM/zEHyRUq7cGaesSw6v4OWqGw=; b=hczRahnHg8ju54pYc8yMKtd8zJWVl8IhnonR+9Mvjw+9itdKlEwwkSXxjzuwCGioSQ GfGizSlNrLNC4EafxQe/TH5qzZEQDP3nIUgDkWnUlTQ8x8myP9xhIRRmrXg2N/X2mbRV etW0KnE9DJ2skbpXFpJgPFR8X4Vp/u/FRMi6g= MIME-Version: 1.0 Received: by 10.42.133.130 with SMTP id h2mr4641094ict.101.1314205611285; Wed, 24 Aug 2011 10:06:51 -0700 (PDT) Received: by 10.231.43.136 with HTTP; Wed, 24 Aug 2011 10:06:51 -0700 (PDT) In-Reply-To: <790E5582101F4A069156B4677843CD78@AGB> References: <790E5582101F4A069156B4677843CD78@AGB> Date: Wed, 24 Aug 2011 18:06:51 +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=90e6ba6e87809f5c0204ab4356d0 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: 0:2:432018592:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d288.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d40834e552fec5e9d X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --90e6ba6e87809f5c0204ab4356d0 Content-Type: text/plain; charset=ISO-8859-1 I know what you're referring to. In cases of impulsive noise, there is a finite probability of something eventually getting through the decoder and being flagged as valid. The very nature of heavy source coding, means that the resulting random output will look like a valid callsign. However, WE then apply the next level of error detection, by knowing the combination must be rubbish. 'jnt [and there is another example of source coding] On 24 August 2011 17:47, Graham wrote: > ** > >> and gives absolutely guaranteed error free decoding, or nothing at > all. << > > Are you sure ? > > G.. > > *From:* Andy Talbot > *Sent:* Wednesday, August 24, 2011 5:12 PM > *To:* rsgb_lf_group@blacksheep.org > *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) = 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/ >> >> > > > --90e6ba6e87809f5c0204ab4356d0 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
I know what you're referring to.=A0 In cases of impulsive noise, t= here is a finite=A0probability of=A0something eventually =A0getting through= the decoder and being flagged as valid.=A0 The very nature of heavy source= coding, means that the resulting random output will look like a valid call= sign.=A0=A0 However, WE then apply the next level of error detection, by kn= owing the combination must be rubbish.
=A0
'jnt=A0=A0 [and there is another=A0example of source coding]


=A0
On 24 August 2011 17:47, Graham <g8fzk@g8fzk.fsnet.co.uk> wrote:
>>=A0 and gives absolutely guaranteed error free decoding, or no= thing at all.=A0 <<
=A0
Are you sure ?=A0
=A0
G..

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
www.g4jnt.com<= /div>
=A0
=A0
=A0
=A0
On 24 August 2011 16:42, Roger Lapthorn <= rogerlapthorn@gmail.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>




--90e6ba6e87809f5c0204ab4356d0--