Return-Path: Received: from mtain-df08.r1000.mx.aol.com (mtain-df08.r1000.mx.aol.com [172.29.64.220]) by air-db09.mail.aol.com (v126.13) with ESMTP id MAILINDB091-85f54b5b2989170; Sat, 23 Jan 2010 11:53:29 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-df08.r1000.mx.aol.com (Internet Inbound) with ESMTP id F09CD3800019D; Sat, 23 Jan 2010 11:53:26 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NYjDn-0006Wx-00 for rs_out_1@blacksheep.org; Sat, 23 Jan 2010 16:52:27 +0000 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NYjDm-0006Wo-3p for rsgb_lf_group@blacksheep.org; Sat, 23 Jan 2010 16:52:26 +0000 Received: from mail-bw0-f221.google.com ([209.85.218.221]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NYjDj-0006hr-Rt for rsgb_lf_group@blacksheep.org; Sat, 23 Jan 2010 16:52:26 +0000 Received: by bwz21 with SMTP id 21so1773162bwz.4 for ; Sat, 23 Jan 2010 08:52:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=cxCvmKG84AxCwXEFzOUc6DtPUphZhK3He8uXLkbEhLQ=; b=gSI8V5TI1c7ijIhtXV2gZluO2cUHn2jMsWZoFHPLu5ZC4aKg8PAdJXQYGF25Xluav4 /uum1td0d44v+bgLReFFs8NczU5rGyTB/o+gBDssO+/DSu1ao03VmQfRAf9zj2sV+vAu ZpMMwM340HC+8IkhCwjL9j9dkKj9cFPDrpAmE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=hubEB8HPCKKqV67IkXd4yrt+b4q8gGid3DpLYHeIUFJ3SAukQVdSBk0AKBHNE33yBu V8nXI/EMX/XJOF/iBfC8qj+wD5nFqa2updZBc+OrMEbaSxtUgW4QpqJv8WL9aYZi1UKR W3Khl24n4WP78qH7xFCRJm0J77w/IbDZmOae0= MIME-Version: 1.0 Received: by 10.204.49.79 with SMTP id u15mr2505340bkf.117.1264265536730; Sat, 23 Jan 2010 08:52:16 -0800 (PST) In-Reply-To: References: <9afca2641001230548m3538db64y92b335aa75c1dc00@mail.gmail.com> <9afca2641001230643s4cf01377h70165d22d325dbe1@mail.gmail.com> Date: Sat, 23 Jan 2010 16:52:16 +0000 Message-ID: <9afca2641001230852x7c870d8r3837c9b6eb60c67b@mail.gmail.com> From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 1.2 (+) X-Spam-Report: autolearn=disabled,BIZ_TLD=1.169,HTML_MESSAGE=0.001 Subject: Re: LF: JT4A simple guide? Content-Type: multipart/alternative; boundary=0003255543f63801dd047dd7c24b X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=BIZ_TLD,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-sid: 3039ac1d40dc4b5b29862b2a X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --0003255543f63801dd047dd7c24b Content-Type: text/plain; charset=ISO-8859-1 Ok, fully understand Andy. Jim G7NKS is sending JT4A but I'm not getting any decodes yet. Roger G3XBM On 23 January 2010 16:38, Andy Talbot wrote: > After posting that, I realised the JT4 PIC/DDS beacon code is designed for > 100% duty cycle operation, viz JT4, CW + carrier, which is a bit antisocial > (certainly the wide bandwidth CW bit). And more importantly, as my PA is a > low efficiency clas AB linear one - enough said... > > To adapt for low duty cycle would need the PIC code changing, so will put > the idea on hold unles there is a real demand. For a beacon, WSPR has more > to offer anyway. > > Incidently, WSPR and JT4 are the same mode anyway, albeit with a bandwidth > change from 1.46 to 4.375Hz with a resulting 4.75dB reduction in S/N. The > coding and demodulation are all the same, so this bandwidth difference > should be directly detectable between the two modes. The differing message > contents wont affect the efficiency, its the added error correction , sync > and modulation that matters - and they use the same algorithm. > > Andy > www.g4jnt.com > > > On 23 January 2010 14:43, Roger Lapthorn wrote: > >> Thanks for this help Andy. >> >> I'd not like to derive others of your valuable 500kHz WSPR beacon, but >> could you beacon in JT4A at certain pre-arranged times or days perhaps? If >> JT4A looks like offering the possibility of really weak signal QSOs to >> people like me running flea-power then I'd like to explore the mode some >> more and having a reliable signal to test with initially would be useful. I >> am sure there will be others who would value this too. >> >> 73s >> Roger G3XBM >> >> >> >> On 23 January 2010 14:26, Andy Talbot wrote: >> >>> AFAIK The is no 'simple guide' JT4x was never originally going to be >>> one of Joe's supported modes, although after our extensive use on uWaves it >>> certainly is now. JT65x was the more popular and documented code, being >>> heavily used for EME on 144 / 432 / 1296MHz, with JT4x just one of those >>> included in the WSJT suite to 'try out' If you download and read the >>> WSJT users guide and other supporting files, there's all you need to know to >>> get it going is in there. >>> >>> http://www.physics.princeton.edu/pulsar/K1JT/WSJT_User_600.pdf >>> *http://www.physics.princeton.edu/pulsar/K1JT/wsjt.html* >>> http://www.physics.princeton.edu/pulsar/K1JT/JT2_JT4.TXT >>> >>> Its still debatable as to whether JT4 is better or worse than JT65x, but >>> at least it does have the options of being available in a range of >>> bandwidths / tone spacings making it usable from DC to red light. >>> (Although I think I've only ever come across A, D and G being used >>> respectively on LF, HF and uWaves) There's probably only a fraction of a >>> dB in it and both are, as far as I can ascertain, only a dB or two away from >>> the Shannon limit. [Which knocks spots off CW or any fuzzy mode, as well as >>> straight PSKnn without error correction]. Wolf has a similar signalling >>> efficiency, but unfortunately is wider, needs a linear TX to avoid being too >>> wide and seems less user friendly. >>> >>> A year or so ago we (the microwave community) wanted something for use on >>> 1.3GHz and up to 10GHz or beyond. JT4G, the widest spaced varient of >>> them looked suitable. After some prompting, Joe was persuaded not to >>> abandon that mode, and in fact he modified the code to enhance the decoder >>> routine so the wide spaced version would be decoded with the same S/N as >>> JT4A. We discovered just how good the mode was, even under severe >>> rainscatter conditions where each tone was spread out to 200Hz bandwidth >>> (tone spacing in JT4G is 315Hz for 1kH zwide overall, so this rain scattered >>> signal still had discrete tone energy). >>> >>> There are now two microwave beacons that transmit JT4G waveforms, the >>> 10 and 2.3GHz ones in Dorset GB3SCX and GB3SCS www.scrbg.org and >>> now GB3CSB on 1.3GHz from central Scotland >>> http://www.rayjames.biz/gm4cxm/id14.html Other will follow before long >>> as it is quite an easy mode to generate from a simple PIC keyer provided >>> accurate timing information is available to keep it synched. >>> >>> My beacon engine - the one that currently drives the 503.7/503.85 signals >>> - can give JT4A immediately just by reprogramming the PIC. Would there be >>> any interest, bearing in mind both the WSPR and "5MHz type" waveforms will >>> be lost for the duration? >>> >>> Andy >>> www.g4jnt.com >>> >>> This email has been scanned for damaging side-effects by the health and >>> safety police, is guaranteed to contain no substances hazardous to health, >>> but may contribute to dissolving the nether and polar regions >>> >>> >>> On 23 January 2010 13:48, Roger Lapthorn wrote: >>> >>>> Having looked on the WSJT website there is little (no?) reference to >>>> JT4A in the help files. I assume it is similar to modes like JT6M which I >>>> have managed to receive in the past on 50MHz but never tried TXing. >>>> >>>> Can someone point me in the direction of a "*JT4A for Dummies*" guide, >>>> or something similar that I might understand, please? >>>> >>>> 73s >>>> Roger G3XBM >>>> >>>> -- >>>> >>>> http://g3xbm-qrp.blogspot.com/ >>>> http://www.g3xbm.co.uk >>>> http://www.youtube.com/user/G3XBM >>>> G3XBM GQRP 1678 ISWL G11088 >>>> >>> >>> >> >> >> -- >> >> http://g3xbm-qrp.blogspot.com/ >> http://www.g3xbm.co.uk >> http://www.youtube.com/user/G3XBM >> G3XBM GQRP 1678 ISWL G11088 >> > > -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/G3XBM G3XBM GQRP 1678 ISWL G11088 --0003255543f63801dd047dd7c24b Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Ok, fully understand Andy.=A0 Jim G7NKS is sending JT4A but I'm not ge= tting any decodes yet.

Roger G3XBM

On 23 January 2010 16:38, Andy Talbot <andy.g4jnt@googlemail.com>= wrote:
After post= ing that, I realised the JT4 PIC/DDS beacon code is designed for 100% duty= cycle operation, viz JT4, CW + carrier, which is a bit antisocial (certai= nly the wide bandwidth CW bit).=A0 And more importantly, as my PA is a low= efficiency clas AB linear one - enough said...
=A0
To adapt for low duty cycle would need the PIC code changing, so will= put the idea on hold unles there is a real demand.=A0=A0 For a beacon, WS= PR has more to offer anyway.
=A0
Incidently, WSPR and JT4 are the same mode anyway, albeit with a band= width change from 1.46 to 4.375Hz=A0 with a resulting 4.75dB reduction in= S/N.=A0 The coding and demodulation are all the same, so this bandwidth= difference should be directly=A0detectable=A0between the two modes.=A0 Th= e differing message contents wont affect the efficiency, its the added err= or correction , sync and modulation=A0that matters - and they use the same= algorithm.
On 23 January 2010 14:43, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:
Thanks for this= help Andy.

I'd not like to derive others of your valuable 500= kHz WSPR beacon, but could you beacon in JT4A at certain pre-arranged time= s or days perhaps? If JT4A looks like offering the possibility of really= weak signal QSOs to people like me running flea-power then I'd like= to explore the mode some more and having a reliable signal to test with= initially would be useful. I am sure there will be others who would value= this too.

73s
Roger G3XBM=20



On 23 January 2010 14:26, Andy Talbot <andy.g4jnt@googlemail.com> wrote:
AFAIK The is no 'simple guide'=A0=A0 JT4x was never originall= y going to be one of Joe's supported modes, although after our extensi= ve use=A0on uWaves it certainly=A0is now.=A0=A0 JT65x was the more popular= and documented code, being heavily used for EME on 144=A0/ 432 /=A01296MH= z,=A0 =A0with JT4x just one of those included in the WSJT suite to 'tr= y out'=A0=A0 If you download and read the WSJT=A0users guide and other= supporting files, there's=A0all you need to know to get it going is= in there.
=A0
=A0
Its still debatable as to whether JT4 is better or worse than JT65x,= but at least it does have the options of being available in a range of ba= ndwidths / tone spacings making it usable from DC to red light.=A0=A0 (Alt= hough I think I've only ever come across A, D and G being used respect= ively on LF, HF and uWaves)=A0=A0=A0 There's probably only a fraction= of a dB in it and both are, as far as I can ascertain, only a dB or two= away from the Shannon limit.=A0 [Which knocks spots off CW or any fuzzy= mode, as well as straight PSKnn=A0without error correction].=A0=A0 Wolf= has a similar signalling efficiency, but unfortunately is wider, needs a= linear TX to avoid being too wide and seems less user friendly.
=A0
A year or so ago we (the microwave community) wanted something for us= e=A0on 1.3GHz and up to 10GHz or beyond.=A0=A0JT4G, the widest spaced vari= ent of them=A0looked suitable.=A0=A0=A0 After some prompting, Joe was pers= uaded not to abandon that mode,=A0 and in fact=A0he=A0modified the code to= =A0enhance the decoder routine so the wide spaced version would be decode= d with the same S/N as JT4A.=A0=A0=A0 We discovered just how good the mode= was, even under severe rainscatter conditions where each tone was spread= out to 200Hz bandwidth (tone spacing in JT4G is 315Hz for 1kH zwide overa= ll, so this rain scattered signal still had discrete tone energy).
=A0
There are now two microwave beacons that transmit JT4G waveforms,=A0= =A0 the 10 and 2.3GHz ones in Dorset=A0 GB3SCX and GB3SCS www.scrbg.org=A0 =A0 and=A0 now GB= 3CSB on 1.3GHz from central Scotland http://www.rayjames.biz/gm4cxm/id14.html= =A0 Other will follow before long as it is quite an easy mode to gener= ate from a simple PIC keyer provided accurate timing information is availa= ble to keep it synched.=A0=A0
=A0
My beacon engine - the one that currently drives the 503.7/503.85 sig= nals -=A0can give JT4A immediately just by reprogramming the PIC.=A0=A0 Wo= uld there be any interest, bearing in mind=A0both the=A0WSPR and "5MH= z type" waveforms will be lost for the duration?

Andy
www.g4jnt.com

This email has been scanned for damaging= side-effects by the health and safety police, is guaranteed to contain no= substances hazardous to health, but may contribute to dissolving the neth= er and polar regions


On 23 January 2010 13:48, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:
Having looked= on the WSJT website there is little (no?)=A0 reference to JT4A in the hel= p files. I assume it is similar to modes like JT6M which I have managed to= receive in the past on 50MHz but never tried TXing.

Can someone point me in the direction of a "JT4A for Dummies" guide, or something similar that I might understand, please?
<= br>73s
Roger G3XBM

--
=
http://g3xbm-= qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/G3XBM
G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088




--

<= a href=3D"http://g3xbm-qrp.blogspot.com/" target=3D"_blank">http://g3xbm-q= rp.blogspot.com/
http://www.g3xbm.co.= uk
= http://www.youtube.com/user/G3XBM
G3XBM =A0 =A0GQRP 1678 =A0 =A0 = =A0ISWL G11088




--

http://g3xbm-qrp.blogspot.com/http://www.g3xbm.co.uk
http://www.youtube.com/user/G3XBM
G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088
--0003255543f63801dd047dd7c24b--