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(VPS 131103-1, 03/11/2013), Outbound message X-Antivirus-Status: Clean X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Jim yes I think it is a phase effect, the reinforcement/cancellation is probably between 2 hop and 3 hop paths. A 16dB fade suggests 20dB or so difference in amplitude. I used to reckon on about a 12dB per ionospheric hop and less, maybe 6dB, for a sea "bounce" based on signal from Joe VO1NA and the Naval station at Newport Corner near Halifax NS. Each hop has a maximum range of about 2000km. There are several effects around the sunset shadow area that could add to the effect too. Higher angles at the ionosphere may penetrate futher before returning giving higher attenuation to the higher hop modes. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [65.20.0.126 listed in list.dnswl.org] 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 4b1739ed9f8a5c36a1958dbdf5306bf7 Subject: LF: Re: RE: Hartmut's Grabber On Last Night... Content-Type: multipart/alternative; boundary="----=_NextPart_000_008E_01CED8EE.06161690" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.1 required=5.0 tests=FORGED_MUA_OUTLOOK,HTML_40_50, 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 Status: O X-Status: X-Keywords: X-UID: 933 This is a multi-part message in MIME format. ------=_NextPart_000_008E_01CED8EE.06161690 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Jim yes I think it is a phase effect, the reinforcement/cancellation = is probably between 2 hop and 3 hop paths. A 16dB fade suggests 20dB or = so difference in amplitude. I used to reckon on about a 12dB per = ionospheric hop and less, maybe 6dB, for a sea "bounce" based on signal = from Joe VO1NA and the Naval station at Newport Corner near Halifax NS. = Each hop has a maximum range of about 2000km. There are several effects = around the sunset shadow area that could add to the effect too. Higher = angles at the ionosphere may penetrate futher before returning giving = higher attenuation to the higher hop modes.=20 A thumbnail calculation suggests hop3 ampltude of about -23dB below hop = 2 would give a 17dB fade as it goes in and out of phase. Very much a "hand waving" estimate but a useful empirical guide. Alan G3NYK ----- Original Message -----=20 From: hvanesce=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Sunday, November 03, 2013 8:56 PM Subject: LF: RE: Hartmut's Grabber On Last Night... Bob, =20 This is the third time that I've noticed Dex's signal peaking = substantially (>15dB?) starting around 0500, at approximately the same = time that your signal begins a substantial fade. I've seen this twice on = captures from Hartmut's grabber, and once on a capture from Mike's = grabber.=20 =20 An interesting example is 21 October 2013, when captures by Henny, = Mike and Hartmut all showed a fade of roughly 10-15dB in your signal = from 0500-0530, with Mike's grabber (which showed Dex's signal clearly = around that time) showing a rise in Dex's signal of roughly 10-15dB. =20 =20 I wonder if this could be attributable to modal phase = reinforcement/cancellation near the terminator? The relative change = between your signal and Dex's seems rather high for that mechanism, but = I suppose not out of the question. AGARD CP 305 includes a paper = (Morfitt) with some interesting plots in this context, and a number of = other papers with interesting propagation studies at frequencies near = 74kHz; is there a good place for me to post info of this type? =20 73, =20 Jim AA5BW=20 =20 From: owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Bob Raide Sent: Sunday, November 3, 2013 12:07 PM To: rsgb_lf_group@blacksheep.org Subject: LF: Hartmut's Grabber On Last Night... =20 Good shots of Me and Dex-Bob WG2XRS/4 NY [XRS4] and [XRS5]...=20 ------=_NextPart_000_008E_01CED8EE.06161690 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Jim yes I think it is a phase = effect, the=20 reinforcement/cancellation is probably between 2 hop and 3 hop paths. A = 16dB=20 fade suggests 20dB or so difference in amplitude. I used to reckon on = about a=20 12dB per ionospheric hop and less, maybe 6dB, for a sea "bounce" based = on signal=20 from Joe VO1NA and the Naval station at Newport Corner near Halifax NS. = Each hop=20 has a maximum range of about 2000km. There are several effects around = the sunset=20 shadow area that could add to the effect too. Higher angles at the=20 ionosphere may penetrate futher before returning giving higher = attenuation to=20 the higher hop modes. 
 
A thumbnail calculation suggests hop3 = ampltude of=20 about -23dB below hop 2 would give a 17dB fade as it goes in and = out of=20 phase.
 
Very much a "hand waving" estimate but = a useful=20 empirical guide.
 
Alan
G3NYK
----- Original Message -----
From:=20 hvanesce=20
Sent: Sunday, November 03, 2013 = 8:56=20 PM
Subject: LF: RE: Hartmut's = Grabber On=20 Last Night...

Bob,

 

This=20 is the third time that I=92ve noticed Dex=92s signal peaking = substantially=20 (>15dB?) starting around 0500, at approximately the same time that = your=20 signal begins a substantial fade. I=92ve seen this twice on captures = from=20 Hartmut=92s grabber, and once on a capture from Mike=92s grabber.=20

 

An=20 interesting example is 21 October 2013, when captures by Henny, Mike = and=20 Hartmut all showed a fade of roughly 10-15dB in your signal from = 0500-0530,=20 with Mike=92s grabber (which showed Dex=92s signal clearly around that = time)=20 showing a rise in Dex=92s signal of roughly 10-15dB.=20  

 

I=20 wonder if this could be attributable to modal phase = reinforcement/cancellation=20 near the terminator? The relative change between your signal and = Dex=92s seems=20 rather high for that mechanism, but I suppose not out of the question. = AGARD=20 CP 305 includes a paper (Morfitt) with some interesting plots in this = context,=20 and a number of other papers with interesting propagation studies at=20 frequencies near 74kHz; is there a good place for me to post info of = this=20 type?

 

73,

 

Jim=20 AA5BW

 

From:=20 owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org]=20 On Behalf Of Bob Raide
Sent: Sunday, November 3, 2013 = 12:07=20 PM
To: rsgb_lf_group@blacksheep.org
Subject: LF: = Hartmut's=20 Grabber On Last Night...

 

Good=20 shots of Me and Dex-Bob WG2XRS/4 NY [XRS4] and [XRS5]...=20

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