Return-Path: Received: from rly-dg11.mx.aol.com (rly-dg11.mail.aol.com [172.19.151.95]) by air-dg06.mail.aol.com (v123.3) with ESMTP id MAILINDG064-60549b1a5ff2e6; Fri, 06 Mar 2009 17:39:02 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dg11.mx.aol.com (v123.3) with ESMTP id MAILRELAYINDG116-60549b1a5ff2e6; Fri, 06 Mar 2009 17:38:57 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Lfigf-0002rJ-1V for rs_out_1@blacksheep.org; Fri, 06 Mar 2009 22:38:37 +0000 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Lfigd-0002rA-Qa for rsgb_lf_group@blacksheep.org; Fri, 06 Mar 2009 22:38:35 +0000 Received: from smtp5.freeserve.com ([193.252.22.151] helo=smtp6.freeserve.com) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Lfigc-0006KT-Ko for rsgb_lf_group@blacksheep.org; Fri, 06 Mar 2009 22:38:35 +0000 Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3526.me.freeserve.com (SMTP Server) with ESMTP id 3AFB01C00083 for ; Fri, 6 Mar 2009 23:38:29 +0100 (CET) Received: from AGB (unknown [91.109.23.203]) by mwinf3526.me.freeserve.com (SMTP Server) with SMTP id 83BC91C00082 for ; Fri, 6 Mar 2009 23:38:28 +0100 (CET) X-ME-UUID: 20090306223828539.83BC91C00082@mwinf3526.me.freeserve.com Message-ID: <830D60A934B1493EA43771AE81385B76@AGB> From: "Graham" To: References: <0566EF6DE20B4249A3E74859BF9BA2C6@AGB> <9C03FBF153AB478A9B0DBC5580CF20D2@AGB> <28FA0F184B25444F8BA2F1EC5FC42C04@AGB> In-Reply-To: Date: Fri, 6 Mar 2009 22:38:27 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8064.206 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8064.206 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Multi-function beacon Content-Type: multipart/alternative; boundary="----=_NextPart_000_0154_01C99EAC.44776A50" 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=HTML_30_40,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-IP: 193.82.116.20 ------=_NextPart_000_0154_01C99EAC.44776A50 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Andy, =20 Thanks for the information, I can see the advantage of the phase reversal si= milar to the navy's chirp radar , pulse-width reduction. =20 The situation is a little convoluted, I was contacted by Robert Hemesley, w= ho has produced a software package that will display by scatter gram the re= turns from the 5 meg pulse system, prior to this Robert had been contacted=20= by Gerhard / DK6NI, with the view to propagation observations on 500 using= the system.=20 =20 I had a quick look at the system with the view to 'creating' a suitable be= acon tx to enable an investigation to take place, however, the pulse para= meter's where not clearly defined, my approach was to use the ma1723 and=20= linear amplifier to produce a beacon transmission from a simple wave file= .. not too high tech but would provide the simple time windows and changes= in carrier levels as defined. But now looks the pulse ranging aspect of the= system is beyond my existing station equipment. =20 The modification of the system looks to quite a task and I assume requires D= DS generation. I had the impression that the rx software measured the time= interval of the pulses and not the absolute time, allowing a normal 'rx sys= tem' to be used for the observation ? =20 Tnx - G ..=20 =20 =20 Nb =20 I have posted details of your beacon in various news groups etc and establis= hed a page on the uk500khz group, using your original post and added a req= uest, 'not to' send log files to the 5 meg group via email ....=20 From: Andy Talbot=20 Sent: Friday, March 06, 2009 9:08 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: Multi-function beacon Graham -=20 I'm not sure I know what you are hoping to do with the sounder pulse. It=20= was incorporated into the 5MHz system to allow propagation investigations in= to multiple skywave hops and multipath, Its parameters were therefore set=20= at values that were a compromise between expected HF multipath parameters, a= nd what could reasonably be allowed for in terms of "necessary bandwidth". =20= While G3PLX did generate some data using the sounder, the idea was never wid= ely popular. In fact there has been recent mention of removing the sounder=20= sequence from at least one of the beacons. A short pulse is not really a g= ood choice, but with only a narrow bandwidth to play width, its the best tha= t could be done. A chirp or PN sequence would be a better solution. Are you hoping to be able to set up some sort of sounding system at MF? If= so, I suspect you're going to want to measure a different range of values a= nd a different waveform would fit the bill better. I know very little abou= t MF/HF propagation beyond what the amateur textbooks give, but suggest you=20= talk to G3PLX, G0MJW and others who do understand the subject very well. Whatever, I suspect you may be interested in accurately measuring the time d= elay changes over long paths, and for this, short pulses are not the answer.= Instead, coherent systems making use of phase information should do the j= ob. These days, its trivial to get sub-microsecond timing accuracy with an= y GPS receiver and I firmly believe this is the way to go.=20 It hasn't been widely made-use-of, but the RAL VHF beacons on 40/50/60/70MHz= , and GB3VHF on 144MHz all have a GPS timed sequence of once per second phas= e reversals as part of their transmission (JT65B, CW, carrier, reversals). =20= These reversals occur at a precise point referred to UTC, and anyone else c= an measure them, and relate to a local GPS reference. Andy G4JNT www.g4jnt.com 2009/3/6 Graham OK Andy,=20 I was thinking more in terms of generating the pulse using 'audio' and no= t by hard keying .. but the 'area under the curve' looks a little 'thin' .= .pity .. the rest of the system could be 'constructed' using a audio edito= r .and sent via a ssb tx with alc 'off' .. how accurate is the start time r= equirements ?=20 tnx- G ..=20 From: Andy Talbot=20 Sent: Friday, March 06, 2009 8:13 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: Multi-function beacon Not strictly -=20 Look at it in th efreqeuncy domain. A 500us pulse has its first zero at 2= 000/pi =3D 637Hz, so most of the energy is within 1300Hz bandwidth, and a su= bstantial part will pass though the Rx filter. It will be extended in time=20= and flattenned, but the detection algorithm finds the peak, in effect applyi= ng an inverse transform of the SSB filter. Andy G4JNT www.g4jnt.com Nb the pulse width , 500uS .. that's a bit sharp for a ssb filter ,=20= only 1.5 cycles at 3 Khz ... ? ----------------------------------------------------------------------------= -- No virus found in this incoming message. Checked by AVG - www.avg.com=20 Version: 8.0.237 / Virus Database: 270.11.8/1987 - Release Date: 03/06/09=20= 07:20:00 ----------------------------------------------------------------------------= ---- No virus found in this incoming message. Checked by AVG - www.avg.com=20 Version: 8.0.237 / Virus Database: 270.11.8/1987 - Release Date: 03/06/09 07= :20:00 ------=_NextPart_000_0154_01C99EAC.44776A50 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Andy,<= /SPAN>

 

Thanks= for the=20 information, I can see the advantage of the phase reversal similar to the na= vy=92s=20 chirp radar , pulse-width reduction.

 

The si= tuation is=20 a little convoluted, I was contacted by =  Robert Hemesley, who has produced a=20 software package that will display by scatter gram the  returns from the 5 meg pulse system,=20 prior to this Robert had been  contacted by  Gerhard / D= K6NI, with the  view to prop= agation observations on 500=20 using the system.

 

I had=20= a quick=20 look at the  system with the  view to =91creating=92 a sui= table beacon tx=20 to  enable an investigation to=   take place, however, the  pulse parameter=92s where no= t clearly=20 defined, my approach  was to  use the  ma1723 and&= nbsp; linear amplifier to  <= /SPAN>produce a beacon  tran= smission from a simple wave file ..=20 not too high tech but would provide the&nb= sp;=20 simple time windows and changes in carrier levels as defined. But now= =20 looks the pulse ranging aspect of the = ;=20 system is beyond my existing station equipment.

 

The mo= dification=20 of the system looks to quite a task and I assume requires DDS generation. I=20= had=20 the  impression that the rx software measured the  time interval o= f=20 the pulses and not the absolute time, allowing a normal 'rx system' to be us= ed=20 for the observation ?

 

Tnx=20= =96 G ..=20

 

 

Nb

 

I have= posted=20 details of your beacon in various news groups etc and established a page on=20 the  uk500khz group, using you= r  original post and added a= request, =91not=20 to=92 send log files to the 5 meg group via email ...


Sent: Friday, March 06, 2009 9:08 PM
Subject: Re: LF: Multi-function beacon

Graham -
 
I'm not sure I know what you are hoping to do with the sounder=20 pulse.    It was incorporated into the 5MHz system to allow=20 propagation investigations into multiple skywave hops and multipath, &n= bsp;=20 Its parameters were therefore set at values that were a compromise between=20 expected HF multipath parameters, and what could reasonably be allowed for i= n=20 terms of "necessary bandwidth".  While G3PLX did generate som= e=20 data using the sounder, the idea was never widely popular.  In fac= t=20 there has been recent mention of removing the sounder sequence from at least= one=20 of the beacons.   A short pulse is not really a good choice, but w= ith=20 only a narrow bandwidth to play width, its the best that could be=20 done.   A chirp or PN sequence  would be a better solution.
 
Are you hoping to be able to set up some sort of sounding system at=20 MF?   If so, I suspect you're going to want to measure a different= =20 range of values and a different waveform would fit the bill better. &nb= sp;=20 I know very little about MF/HF propagation beyond what the amateur textbooks= =20 give, but suggest you talk to G3PLX, G0MJW and others who do understand the=20 subject very well.
 
Whatever, I suspect you may be interested in accurately measuring=20= the=20 time delay changes over long paths, and for this, short pulses are not = the=20 answer.   Instead, coherent systems making use of phase informatio= n=20 should do the job.   These days, its trivial to get=20 sub-microsecond timing accuracy with any GPS receiver and I firmly beli= eve=20 this is the way to go. 
 
It hasn't been widely made-use-of, but the RAL VHF beacons on=20 40/50/60/70MHz, and GB3VHF on 144MHz all have a GPS timed sequence of o= nce=20 per second phase reversals as part of their transmission (JT65B, CW, carrier= ,=20 reversals).   These reversals occur at a precise point referred to= =20 UTC, and anyone else can measure them, and relate to a local GPS=20 reference.

Andy  G4JNT
= www.g4jnt.com


2009/3/6 Graham <g8fzk@g8fzk.fsnet.co.uk>
OK  Andy,
 
I was thinking more in terms of generatin= g=20 the  pulse using 'audio' and not by hard keying .. but the 'area unde= r=20 the  curve' looks a little 'thin'  ..pity .. the  rest of=20 the  system could be 'constructed' using a audio editor .and sent via= a=20 ssb tx with alc 'off' .. how accurate is the  start time requirements= ?=20
 
tnx- G ..
 
 

Sent: Friday, March 06, 2009 8:13 PM
Subject: Re: LF: Multi-function beacon

Not strictly -
Look at it in th efreqeuncy domain.  A 500us pulse has its first= =20 zero at 2000/pi =3D 637Hz, so most of the energy is within 1300Hz bandwidt= h,=20 and a substantial part will pass though the Rx filter.  It will=20= be=20 extended in time and flattenned, but the detection algorithm finds the pea= k,=20 in effect applying an inverse transform of the SSB filter.

Andy  G4JNT
www.g4jnt.com

 
 
Nb   the  pulse width , 500uS= ..=20 that's a bit  sharp for a ssb filter , only  1.5 cycles at 3 K= hz=20 ... ?
 
 
 
 


No virus found in this incoming message.
Checked by AVG - www.avg.com
= Version:=20 8.0.237 / Virus Database: 270.11.8/1987 - Release Date: 03/06/09 07:20:00<= BR>



No virus found in this incoming message.
Checked by AVG -=20 www.avg.com
Version: 8.0.237 / Virus Database: 270.11.8/1987 - Release D= ate:=20 03/06/09 07:20:00
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