Return-Path: Received: from mtain-dc01.r1000.mx.aol.com (mtain-dc01.r1000.mx.aol.com [172.29.64.129]) by air-de06.mail.aol.com (v126.13) with ESMTP id MAILINDE063-5eb84b5b264916d; Sat, 23 Jan 2010 11:39:37 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dc01.r1000.mx.aol.com (Internet Inbound) with ESMTP id CDB95380000BD; Sat, 23 Jan 2010 11:39:35 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NYj0B-0006QC-9P for rs_out_1@blacksheep.org; Sat, 23 Jan 2010 16:38:23 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NYj0A-0006Q3-J1 for rsgb_lf_group@blacksheep.org; Sat, 23 Jan 2010 16:38:22 +0000 Received: from mail-fx0-f221.google.com ([209.85.220.221]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NYj07-0004PO-Tn for rsgb_lf_group@blacksheep.org; Sat, 23 Jan 2010 16:38:22 +0000 Received: by fxm21 with SMTP id 21so369249fxm.29 for ; Sat, 23 Jan 2010 08:38:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=gh4Ga2urNvuazWn8vppiQF11TEOEtvrMO5sNp8D7F2Q=; b=UsnQrsuWLJZ+ZK6vq5fCrQvTcXJcXZy06aGzCNgz9eytORRVPS32wjtrREkWPZMDch xtM/FASox5qngfXGNm0ZIU0f+8T6PmIrfV5yP7U/oSXQQyX/hCQWNfLah+rR9OaO6vv0 x7FdXogKuJOsdI0HGIb3Fcws+Xp3hyl4YiIFQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=Cg5yvJNX6vCET8XSYFiDWZeJaQbTw5e46yB4whPPhfAL1XclEvYearOb8hv62PhoZa W+Ah+QWQet0S5mBAfn5biEGRT795zkA1oIi0yCiuywNDrtNHF1zm3ZF2Uv2vdDfmB+/2 pg2KmJPoesdlp4BMrKn/U0HvH0WNLu8EM4vDM= MIME-Version: 1.0 Received: by 10.239.191.203 with SMTP id c11mr494528hbi.65.1264264691145; Sat, 23 Jan 2010 08:38:11 -0800 (PST) In-Reply-To: <9afca2641001230643s4cf01377h70165d22d325dbe1@mail.gmail.com> References: <9afca2641001230548m3538db64y92b335aa75c1dc00@mail.gmail.com> <9afca2641001230643s4cf01377h70165d22d325dbe1@mail.gmail.com> Date: Sat, 23 Jan 2010 16:38:11 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: JT4A simple guide? Content-Type: multipart/alternative; boundary=001485f03c94d15c7a047dd78f19 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: 3039ac1d40814b5b264777a4 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --001485f03c94d15c7a047dd78f19 Content-Type: text/plain; charset=ISO-8859-1 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 > --001485f03c94d15c7a047dd78f19 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
After posting that, I realised the JT4 PIC/DDS beacon code is designe= d for 100% duty cycle operation, viz JT4, CW + carrier, which is a bit ant= isocial (certainly 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 500kHz WSPR beacon= , but could you beacon in JT4A at certain pre-arranged times or days perha= ps? 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 mod= e 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 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?
<= 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

--001485f03c94d15c7a047dd78f19--