Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dd06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9A1F238000056; Wed, 24 Aug 2011 17:50:24 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QwLK4-0000dx-0f for rs_out_1@blacksheep.org; Wed, 24 Aug 2011 22:49:20 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QwLK3-0000do-7w for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 22:49:19 +0100 Received: from smtp6.freeserve.com ([193.252.22.190]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QwLK0-00016J-UI for rsgb_lf_group@blacksheep.org; Wed, 24 Aug 2011 22:49:19 +0100 Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3613.me.freeserve.com (SMTP Server) with ESMTP id E7CA87000081 for ; Wed, 24 Aug 2011 23:49:10 +0200 (CEST) Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3613.me.freeserve.com (SMTP Server) with ESMTP id DB3357000082 for ; Wed, 24 Aug 2011 23:49:10 +0200 (CEST) Received: from AGB (unknown [2.26.17.7]) by mwinf3613.me.freeserve.com (SMTP Server) with SMTP id 508697000081 for ; Wed, 24 Aug 2011 23:49:08 +0200 (CEST) X-ME-UUID: 20110824214908329.508697000081@mwinf3613.me.freeserve.com Message-ID: From: "Graham" To: References: <790E5582101F4A069156B4677843CD78@AGB> In-Reply-To: Date: Wed, 24 Aug 2011 22:49:07 +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_0029_01CC62B0.0859C9D0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.0 required=5.0 tests=HTML_30_40, 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: 0:2:471898368:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d40924e557220101a 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_0029_01CC62B0.0859C9D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable It would be nice to start , with the opening statement 'all things = being equal' but as 'we' all know that not quite the case , one = of the problems being , not all stations can send all the modes = and then not all can translate from audio .. so even if say WSPR = or Ros MF or EME where to be more efficient , not all can join = in . >From a communicating efficiency point of view, MFSK will offer = a higher efficiency compared to single tone, but , as can be = observed , LF operations tend to take place in extended time scale = so gain from time integration has tended to be the path taken .. = =20 QRSS Visual observation of course is similar to the final wspr = 'overlook' but with the ability to re-construct what's perhaps = more likely , but in contrast, the amount of data sent via wspr = is limited and cannot be used as a qso mode , it was developed as = a beacon and as Jim notes , is capable of decoding with only = partial reception of the transmitted 'pulse' I think there are 18 = frames ?, the arguments continue as to beacon or data mode .. =20 There is of course the other mode ....=20 In on air tests , I have observed the ROS-MF-1 system operating = some 2 to 3 db lower than the cut off point of wspr , whilst = running at 36 characters/minute, the MF modes (and EME) modes use = only an algorithmic approach to data processing , there being = -no- randomisation deployed in the MF or EME modes , a simple test = , observing a beacon, shows an identical pattern for each = transmission. The modulation being phase continues mfsk avails itself to non = liner systems, one trick developed with Gary G4WGT , is to double = the drive frequency , then present to the logic drive of a class = e/d amp , resulting in the correct tone spacing , this should = work with WSPR , I think Gary has tested this as well (Not = required if you are using a complimentary out put stage ! )=20 MF and the EME mode are true data modes , unfortunately the link = to the MF- DDS 'project' has been removed in later versions , as = that did present a way of generating at LF, perhaps with the = advance of the SDR , the tx side may follow .. ? as winter = approaches ,its not beyond possibility that with a pool of interest = and a couple of emails ... progress could be made ! 73 -G..=20 From: Andy Talbot=20 Sent: Wednesday, August 24, 2011 6:06 PM To: rsgb_lf_group@blacksheep.org=20 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_0029_01CC62B0.0859C9D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
It  would be nice to  start , = with=20 the  opening  statement  'all  things being =20 equal'  but  as 'we' all  know   that  = not =20 quite the  case , one of the  problems being ,  not  = all  stations  can send all  the  modes and then = not =20 all  can  translate  from  audio .. so  even = if =20 say WSPR  or Ros  MF or  EME  where  = to =20 be  more  efficient , not  all can join in = .
 
From a  communicating = efficiency =20 point  of  view,   MFSK  will  offer  = a =20 higher  efficiency  compared to   single  tone, = but , as can be  observed  , LF operations tend  = to =20 take  place in extended  time scale  so  gain from = time=20 integration   has tended  to  be the path  = taken=20  ..  
 
QRSS  Visual   = observation  of=20 course is similar  to   the  final   = wspr =20 'overlook'  but  with the  ability to   = re-construct=20 what's perhaps   more  likely , but  in contrast,=20 the   amount of  data  sent  via  = wspr  is=20 limited and   cannot  be used as a  qso  mode , = it=20 was  developed as a  beacon and as Jim notes , is = capable =20 of   decoding with  only =  partial reception  of=20 the  transmitted 'pulse'  I think there = are   18 frames=20 ?,  the  arguments continue as to  beacon or  = data =20 mode ..   
 
There  is  of course  = the =20 other  mode  ....
 
In  on air  tests  = , I=20 have   observed  the  ROS-MF-1 system   = operating=20 some   2  to  3  db  lower than the  = cut=20 off  point  of wspr , whilst   running at 36 characters/minute, the  MF modes  = (and =20 EME)  modes use  only an algorithmic  approach  = to =20 data  processing  , there  being  -no-  = randomisation=20 deployed  in the  MF or  EME  modes , a  = simple=20 test , observing a  beacon, shows an identical   pattern=20 for  each  transmission.
 
The  modulation  being  = phase=20 continues  mfsk  avails  itself to  non  liner = systems,=20 one  trick   developed  with  Gary G4WGT =  , is=20 to  double the  drive  frequency , then  present to=20 the  logic  drive  of a  class  e/d  = amp  ,=20 resulting  in the  correct  tone  spacing , = this  =20 should   work  with WSPR , I think  Gary  has=20 tested  this  as well   (Not  required  = if =20 you  are  using a  complimentary out put stage ! )=20
 
MF and the EME mode  are  = true =20 data  modes  , unfortunately  the  link  = to  the=20 MF- DDS  'project' has been  removed in later  versions , = as=20 that  did present  a  way of   generating  = at LF,=20 perhaps  with the  advance of the  SDR , the  = tx =20 side  may follow .. ? as   winter  approaches = ,its not=20 beyond possibility that  with  a pool of interest  and = a =20 couple of  emails  ... progress could be made !
 
73 -G..
 
 
 
 

From: Andy Talbot
Sent: Wednesday, August 24, 2011 6:06 PM
To: rsgb_lf_group@blacksheep.org= =20
Subject: Re: LF: WSPR or QRSS: which is = better?

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

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