Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-md05.r1000.mx.aol.com (Internet Inbound) with ESMTP id B566538000157; Wed, 24 Aug 2011 13:54:55 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QwHe9-00085Q-Rz for rs_out_1@blacksheep.org; Wed, 24 Aug 2011 18:53:49 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QwHe8-00085H-UC for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 18:53:48 +0100 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QwHe7-0007Zz-Sf for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 18:53:48 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ArsAAAM4VU5cHnFK/2dsb2JhbABClBsDhAWPWHiBOQIFAQEFCAEBAzwNAhMZAgMFAgEDEQQBAQolFAEECBIGFggGEwoBAgIBAYdiArs/hkkEglGEYZVehwU X-IronPort-AV: E=Sophos;i="4.68,276,1312153200"; d="scan'208,217";a="357797139" Received: from host-92-30-113-74.as13285.net (HELO xphd97xgq27nyf) ([92.30.113.74]) by out1.ip03ir2.opaltelecom.net with SMTP; 24 Aug 2011 18:48:41 +0100 Message-ID: <007f01cc6286$0f541490$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <790E5582101F4A069156B4677843CD78@AGB> Date: Wed, 24 Aug 2011 18:48:40 +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_007C_01CC628E.70DCD320" 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: 0:2:440278848:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d60594e553aee4436 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_007C_01CC628E.70DCD320 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Jim take NOTE Impulsive noise generates a random output that looks like a valid = callsign so this is also inventing a signal that you imagine to exist. An immediate positive ID, don't depend on it !! An appliance communications operator is easily hoodwinked. Bletchley Park CW expert Radio Operators managed to piece messages = together and achieved the object., and no doubt used imagination.=20 No expertise is need to send/receive wspr and for that matter a lot of = other appliance operator modes, know in the services today as IDIOT = PROOF comms black boxes. For a commercial operator that needs to shift thousands of messages = worldwide then automated digital modes are necessary and useful, but for = a radio hobbyist its like using a sledge hammer to crack the proverbial = nut g3kev Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, August 24, 2011 6:06 PM Subject: Re: LF: WSPR or QRSS: which is better? 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] =20 On 24 August 2011 17:47, Graham wrote: >> 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_007C_01CC628E.70DCD320 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Jim take NOTE
Impulsive noise generates a random output that = looks like=20 a valid callsign so this is also inventing a signal that you = imagine to=20 exist.
An immediate positive ID, don't depend on it=20 !!
An appliance communications operator is easily=20 hoodwinked.
Bletchley Park CW  expert Radio = Operators=20 managed to piece messages together and achieved the object., and no = doubt used=20 imagination.
No expertise is need to send/receive wspr and = for that=20 matter a lot of other appliance operator modes, know in the services = today as=20 IDIOT PROOF comms black boxes.
For a commercial operator that needs to shift = thousands of=20 messages worldwide then automated digital modes are necessary and = useful, but=20 for a radio hobbyist its like using a sledge hammer to crack the = proverbial=20 nut
 
g3kev
 
 
 
 
 Original Message -----
From:=20 Andy=20 Talbot
Sent: Wednesday, August 24, = 2011 6:06=20 PM
Subject: Re: LF: WSPR or QRSS: = which is=20 better?

I know what you're referring to.  In cases of impulsive = noise, there=20 is a finite probability of something eventually =  getting=20 through the decoder and being flagged as valid.  The very nature = of heavy=20 source coding, means that the resulting random output will look like a = valid=20 callsign.   However, WE then apply the next level of error=20 detection, by knowing the combination must be rubbish.
 
'jnt   [and there is another example of source=20 coding]


 
On 24 August 2011 17:47, Graham <g8fzk@g8fzk.fsnet.co.uk>=20 wrote:
>>  and gives absolutely guaranteed error free = decoding, or=20 nothing at all.  <<
 
Are you sure ? 
 
G..

From: Andy Talbot =
Sent: Wednesday, August 24, 2011 5:12 PM
Subject: Re: LF: WSPR or QRSS: which is=20 better?

WSPR works in a 1.46Hz signal bandwidth and because of its = very=20 high level of error correction and soft-decision decoding, means=20 that it will work at a S/N of about 3dB in this bandwidth, and=20 sometimes a bit lower still  (Normally, FSK with no correction = at=20 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=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=20 will have to be narrower to get a 2dB higher S/N and works out as=20 1.46 / 10^(2/10) =3D 0.92Hz
 
So QRSS used with a 0.9Hz bandwidth - which I think means about = a 2 -=20 3s dot period ought to be decoded at the same S/N as a WSPR=20 signal.   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=20 all.  About 12 characters in actuality, but that is being = a bit=20 unfair as the coding forces certain callsign and locator=20 formatting.   So in all probablility, more like 7 or 8 = effective=20 characters (I'm being a bit empirical here)
 
Assuming standard QRSS - not DFCW - , which if like standard = Morse,=20 then 5 characters takes about 50 dot symbols to send (12WPM =3D 60 = chars in 1=20 minute, =3D 1 char / second, or about 10 dot periods /=20 second.    Dot speed =3D WPM / 1.2)   If we have = 2s dots,=20 that is 5 characters can be sent in the time for a WSPR=20 transmission.
 
So as a quick estimate, WSPR wins by roughly 2dB in S/N = terms for=20 a given dot period / noise bandwidth.  And at similar S/N = values, WSPR=20 is about 1.5 times faster
Andy
 
 
 
 
On 24 August 2011 16:42, Roger Lapthorn = <rogerlapthorn@gmail.com> 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/

=




<= /BLOCKQUOTE> ------=_NextPart_000_007C_01CC628E.70DCD320--