Return-Path: Received: from mtain-mi03.r1000.mx.aol.com (mtain-mi03.r1000.mail.aol.com [172.21.131.161]) by air-mc03.mail.aol.com (v129.4) with ESMTP id MAILINMC033-a8dd4d700b8536b; Thu, 03 Mar 2011 16:43:33 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mi03.r1000.mx.aol.com (Internet Inbound) with ESMTP id DB21B38000092; Thu, 3 Mar 2011 16:43:30 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PvGHe-0000Go-41 for rs_out_1@blacksheep.org; Thu, 03 Mar 2011 21:42:06 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PvGHd-0000Gf-Dt for rsgb_lf_group@blacksheep.org; Thu, 03 Mar 2011 21:42:05 +0000 Received: from imr-da02.mx.aol.com ([205.188.105.144]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PvGHa-0005OV-L8 for rsgb_lf_group@blacksheep.org; Thu, 03 Mar 2011 21:42:05 +0000 Received: from mtaout-da04.r1000.mx.aol.com (mtaout-da04.r1000.mx.aol.com [172.29.51.132]) by imr-da02.mx.aol.com (8.14.1/8.14.1) with ESMTP id p23LfrLm030620 for ; Thu, 3 Mar 2011 16:41:53 -0500 Received: from White (nrbg-4dbf9fac.pool.mediaWays.net [77.191.159.172]) by mtaout-da04.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id ACB44E000110 for ; Thu, 3 Mar 2011 16:41:52 -0500 (EST) Message-ID: From: "Markus Vester" To: References: <6C9E0C3D501744C99E11539B7AFCB120@IBM7FFA209F07C> <851E08B3D5AD4CC1BE6959CA1293720D@IBM7FFA209F07C> Date: Thu, 3 Mar 2011 22:42:12 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Topband Test Content-Type: multipart/alternative; boundary="----=_NextPart_000_0027_01CBD9F4.3CA89580" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_40_50,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-sid: 3039400cdecb4d700b8246d5 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_0027_01CBD9F4.3CA89580 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Andy, I'll bet against that ;-)=20 If I recall right, Richard G3CWI used to have interesting Doppler plot= s and scattergrams from G3PLX on his website (eg. http://www.qsl.net/g= 3cwi/scatterg.htm). It seems that ionospheric Doppler spectra appear= mostly rather diffuse. On the other hand, in my opinion the sharpness= of the slant line in Chris' capture proves that a point-like object= was moving along a regular, well defined trajectory. If you look to the left of the spectrogram, you can see bits of the Do= ppler shifted line below main line, ie on the high frequency side from= the carrier. Then it crosses over and reappears LF. This would be typ= ical for an aircraft approaching, passing by the baseline at a certain= minimum distance from the baseline, and then receding. It would be interesting to compare future HF Doppler observations to= one of the ADS-B aircraft tracking sites, eg. http://www.flightradar2= 4.com/about.php#!/ or http://www.openatc.com/ . Best regards, Markus (DF6NM) From: Chris=20 Sent: Thursday, March 03, 2011 9:54 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: Topband Test Thanks again Andy and Markus, Yes, my feeling is that the reflective wave shift is due to doppler as= the layer changes height. We need to try it again over a longer perio= d. It is true there are a lot of aircraft between us, but would the re= sult have been so smooth? Has this effect been seen on 137kHz? The info I have seen on near vert= ical incidence/reflection suggest it should. Any thoughts on this appreciated, thanks for taking the time to commen= t. Chris, G4AYT. ----- Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, March 03, 2011 8:40 PM Subject: Re: LF: Topband Test No, it definitely is due to ionospheric shift. 30m/s is no big dea= l over the period of the day/night transition. 30 minutes at that spe= ed would be a mean change in height of 54km. Not unrealistic for an= E layer (??) height of 120km Try to find a copy of G3PLX's article 'JNT =20 On 3 March 2011 20:19, Markus Vester wrote: Hi Chris, thanks for sharing this unusual observation. From your screenshot, the split was up to about 0.35 Hz, or 0.2 pp= m of 1.8 MHz. Interpreted as Doppler, a reflector would have to move= at least 30m/s radially from your baseline. This seems a bit fast for= an ionospheric day-to-night shift. Another possible explanation could be airplane scatter. Large airl= iners are known to have a large radar cross section at HF. Seeing that= on 160 m may seem extreme, but considering the wingspan of an A-380= (80 m), half-wave resonant scattering is a very real possibility. The= downward slope of the Doppler shifted frequency would also be indicat= ive of an object passing by at constant linear velocity. Best 73, Markus (DF6NM) From: Chris=20 Sent: Thursday, March 03, 2011 7:55 PM To: RSGB LF Group=20 Subject: LF: Topband Test Hi All, Yesterday evening Pete, M0FMT, transmitted QRSS on topband for a= test. An unexpected effect was noticed with the trace splitting in tw= o. Nothing new or 'earth shattering' I expect, but new to us and worth= y of further experimentation. See the result and conclusion on my website http://qsl.net/g4ayt= on the bottom of page 1. I have never seen this effect on 137, even with quite strong audib= le signals, maybe others have. Vy 73, Chris, G4AYT, Whitstable, UK. ------=_NextPart_000_0027_01CBD9F4.3CA89580 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Andy, I'll bet against that ;= -)=20
 
If I recall right, Richard G3CWI used= =20 to have interesting Doppler plots and scattergrams from = ;G3PLX on=20 his website (eg. h= ttp://www.qsl.net/g3cwi/scatterg.htm). It=20 seems that ionospheric Doppler spectra appear mostly rather diffu= se. On the=20 other hand, in my opinion the sharpness of the slant line in= Chris'=20 capture proves that a point-like object was moving along a= regular,=20 well defined trajectory.
 
If you look to the left of the= spectrogram,=20 you can see bits of the Doppler shifted line below main line,&nbs= p;ie on=20 the high frequency side from the carrier. Then it crosses ov= er and=20 reappears LF. This would be typical for an=20 aircraft approaching, passing by the baseline at a certain= minimum=20 distance from the baseline, and then receding.
 
It would be interesting to compare&nb= sp;future=20 HF Doppler observations to one of the ADS-B aircraft tracking sit= es, eg. http://www.flightradar24.com/about.php#!/=  or=20 http://www.openatc.com/ = ;.
 
Best regards,
Markus (DF6NM)
 
From: Chris
Sent: Thursday, March 03, 2011 9:54 PM
Subject: Re: LF: Topband Test
=
Thanks again Andy and Markus,<= /DIV>
Yes, my feeling is that the reflectiv= e=20 wave shift is due to doppler as the layer changes height. We need= to try it=20 again over a longer period. It is true there are a lot of aircraft bet= ween us,=20 but would the result have been so smooth?
Has this effect been seen on 137kHz?= The info I=20 have seen on near vertical incidence/reflection suggest it should.
Any thoughts on this appreciated, tha= nks for taking=20 the time to comment.
Chris, G4AYT.
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Thursday, March 03, 201= 1 8:40=20 PM
Subject: Re: LF: Topband Test=
= <= FONT face=3DArial size=3D2>
No, it definitely is due to ionospheric shift. &= nbsp;=20 30m/s is no big deal over the period of the day/night=20 transition.  30 minutes at that speed would be a mean change in= =20 height of 54km.   Not  unrealistic for an E= layer=20 (??) height of 120km
 
Try to find a copy of G3PLX's article
 
'JNT
=

 
On 3 March 2011 20:19, Markus Vester <markusv= ester@aol.com>=20 wrote:
Hi Chris, thanks for sharing this= unusual=20 observation.
 
From your screenshot, the split= was up to about=20 0.35 Hz, or 0.2 ppm of 1.8 MHz. Interpreted as Doppler, = a=20 reflector would have to move at least 30m/s radially from your=20 baseline. This seems a bit fast for an=20 ionospheric day-to-night shift.
 
Another possible explanation coul= d be airplane=20 scatter. Large airliners are known to have a large radar= cross=20 section at HF. Seeing that on 160 m may seem extreme,=20 but considering the wingspan of an A-380 (80 m), ha= lf-wave=20 resonant scattering is a very real possibility. The downward= =20 slope of the Doppler shifted frequency would also be=20 indicative of an object passing by at constant linear=20 velocity.
 
Best 73,
Markus (DF6NM)

From: Chris
Sent: Thursday, March 03, 2011 7:55 PM
Subject: LF: Topband Test

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