Return-Path: Received: from rly-dg06.mx.aol.com (rly-dg06.mail.aol.com [172.19.151.90]) by air-dg08.mail.aol.com (v123.3) with ESMTP id MAILINDG083-5d449b190d730e; Fri, 06 Mar 2009 16:08:57 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dg06.mx.aol.com (v123.3) with ESMTP id MAILRELAYINDG067-5d449b190d730e; Fri, 06 Mar 2009 16:08:42 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1LfhHN-0001Zd-Tt for rs_out_1@blacksheep.org; Fri, 06 Mar 2009 21:08:25 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1LfhHN-0001ZU-8S for rsgb_lf_group@blacksheep.org; Fri, 06 Mar 2009 21:08:25 +0000 Received: from mail-bw0-f164.google.com ([209.85.218.164]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1LfhHM-0003BC-6x for rsgb_lf_group@blacksheep.org; Fri, 06 Mar 2009 21:08:25 +0000 Received: by bwz8 with SMTP id 8so604658bwz.4 for ; Fri, 06 Mar 2009 13:08:18 -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=fhFJOevvfliWartIjrGPRgBHKs8TwLb/RKIIJrDvzA8=; b=Cq6bGFyf3UdJSuVmwXZQkaW8eM8msL0lp6p+JAtwhiEWv67KCbI3oq7mADcMk3D2TS B5A1XjXFlKjgk3v5R703F/2WdybJvMQbn06u9b0PhHApv/ZKHKAjfkjy5TSMdDvUCKW1 5mM850fJgEfcY+im822NR48DqycbQw/sRe0mc= 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=vgDQuLqQbpcCuasLZW97SfEulOMkvjXtvWS+8m329vxYf8R8MfMz0kW7m9YLOwf8+Q kh4ZEJt6N2CWvOmmXUT8BibN/xKi4PXZmpxIB7LKgKsAcCETzV+DYBve0hp039e+jT/c cCSUhGDx869wJuk2zITXbPsZExdfIQFdRm3pE= MIME-Version: 1.0 Received: by 10.223.126.69 with SMTP id b5mr2426218fas.54.1236373698226; Fri, 06 Mar 2009 13:08:18 -0800 (PST) In-Reply-To: <28FA0F184B25444F8BA2F1EC5FC42C04@AGB> References: <0566EF6DE20B4249A3E74859BF9BA2C6@AGB> <9C03FBF153AB478A9B0DBC5580CF20D2@AGB> <28FA0F184B25444F8BA2F1EC5FC42C04@AGB> Date: Fri, 6 Mar 2009 21:08:18 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Karma: unknown: DomainKey-Status: good (testing) 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=001636c5a82f17b134046479afe7 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m273.2 ; domain : googlemail.com DKIM : pass X-Mailer: Unknown (No Version) --001636c5a82f17b134046479afe7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Graham - I'm not sure I know what you are hoping to do with the sounder pulse. It was incorporated into the 5MHz system to allow propagation investigations into multiple skywave hops and multipath, Its parameters were therefore set at values that were a compromise between expected HF multipath parameters, and what could reasonably be allowed for in terms of "necessary bandwidth". While G3PLX did generate some data using the sounder, the idea was never widely popular. In fact there has been recent mention of removing the sounder sequence from at least one of the beacons. A short pulse is not really a good choice, but with only a narrow bandwidth to play width, its the best that 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 and a different waveform would fit the bill better. I know very little about MF/HF propagation beyond what the amateur textbooks give, but suggest you 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 delay changes over long paths, and for this, short pulses are not the answer. Instead, coherent systems making use of phase information should do the job. These days, its trivial to get sub-microsecond timing accuracy with any GPS receiver and I firmly believe this is the way to go. 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 phase reversals as part of their transmission (JT65B, CW, carrier, reversals). These reversals occur at a precise point referred to UTC, and anyone else can measure them, and relate to a local GPS reference. Andy G4JNT www.g4jnt.com 2009/3/6 Graham > OK Andy, > > I was thinking more in terms of generating the pulse using 'audio' and not > 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 > editor .and sent via a ssb tx with alc 'off' .. how accurate is the start > time requirements ? > > tnx- G .. > > > > *From:* Andy Talbot > *Sent:* Friday, March 06, 2009 8:13 PM > *To:* rsgb_lf_group@blacksheep.org > *Subject:* Re: LF: Multi-function beacon > > Not strictly - > Look at it in th efreqeuncy domain. A 500us pulse has its first zero at > 2000/pi = 637Hz, so most of the energy is within 1300Hz bandwidth, and a > substantial part will pass though the Rx filter. It will be extended in > time and flattenned, but the detection algorithm finds the peak, in effect > applying 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 , >> only 1.5 cycles at 3 Khz ... ? >> >> >> >> >> > ------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.0.237 / Virus Database: 270.11.8/1987 - Release Date: 03/06/09 > 07:20:00 > > --001636c5a82f17b134046479afe7 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Graham -
=A0
I'm not sure I know what you are hoping to do with the sounder puls= e.=A0=A0=A0 It was incorporated into the 5MHz system to allow propagation in= vestigations into multiple skywave hops and multipath,=A0=A0 Its parameters=20= were therefore set at values that were a compromise between expected HF mult= ipath parameters, and what could reasonably be allowed for in terms of "= ;necessary=A0bandwidth".=A0=A0While G3PLX did generate some data using=20= the sounder, the idea=A0was never widely popular.=A0 In fact there has been=20= recent mention of removing the sounder sequence from at least one of the bea= cons.=A0=A0 A short pulse is not really a good choice, but with only a narro= w bandwidth to play width, its the best that could be done.=A0=A0 A chirp or= PN sequence =A0would be a better solution.
=A0
Are you hoping to be able to set up some sort of sounding system at MF?= =A0=A0 If so, I suspect you're going to want to measure a different rang= e of values and a different waveform would fit the bill better.=A0=A0 I know= very little about MF/HF propagation beyond what the amateur textbooks give,= but suggest you talk to G3PLX, G0MJW and others who do understand the subje= ct very well.
=A0
Whatever, I suspect=A0you may be interested in accurately measuring the= time delay changes over long paths, and for this, short pulses are not=A0th= e answer.=A0=A0 Instead, coherent systems making use of phase information sh= ould do the job.=A0=A0 These days,=A0its trivial to get sub-microsecond timi= ng accuracy with=A0any GPS receiver and I firmly believe this is the way to=20= go.=A0
=A0
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=A0timed sequence of once per=20= second phase reversals as part of their transmission (JT65B, CW, carrier, re= versals).=A0=A0 These reversals occur at a precise point referred to UTC, an= d anyone else can measure them, and relate to a local GPS reference.

Andy =A0G4JNT
www= .g4jnt.com


2009/3/6 Graham <g8fzk@g8fzk.fsnet.co.uk>
OK=A0 Andy,
=A0
I was thinking more in terms of generat= ing the=A0 pulse using 'audio' and not by hard keying .. but the = 9;area under the=A0 curve' looks a little 'thin'=A0 ..pity .. th= e=A0 rest of the=A0 system could be 'constructed' using a audio edit= or .and sent via a ssb tx with alc 'off' .. how accurate is the=A0 s= tart time requirements ?
=A0
tnx- G ..
=A0
=A0

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

Not strictly -
Look at it in th efreqeuncy domain.=A0 A 500us pulse has its first zero= at 2000/pi =3D 637Hz, so most of the energy is within 1300Hz bandwidth, and= =A0a substantial part will pass though the Rx filter.=A0 It will be extended= in time and flattenned, but the detection algorithm finds the peak, in effe= ct applying an inverse transform of the SSB filter.

Andy =A0G4JNT
www.g4jnt.com

=A0
=A0
Nb =A0 the=A0 pulse width , 500uS .. th= at's a bit=A0 sharp for a ssb filter , only=A0 1.5 cycles at 3 Khz ... ?=
=A0
=A0
=A0
=A0


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


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