Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-me02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 49CE138000094; Fri, 3 May 2013 06:30:40 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UYCjF-0008KZ-90 for rs_out_1@blacksheep.org; Fri, 03 May 2013 10:56:37 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UYCjE-0008KP-GP for rsgb_lf_group@blacksheep.org; Fri, 03 May 2013 10:56:36 +0100 Received: from nm2-vm7.bt.bullet.mail.ir2.yahoo.com ([212.82.99.225]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1UYCjC-00030v-3z for rsgb_lf_group@blacksheep.org; Fri, 03 May 2013 10:56:35 +0100 Received: from [212.82.98.47] by nm2.bt.bullet.mail.ir2.yahoo.com with NNFMP; 03 May 2013 09:56:13 -0000 Received: from [46.228.39.164] by tm8.bt.bullet.mail.ir2.yahoo.com with NNFMP; 03 May 2013 09:56:13 -0000 Received: from [127.0.0.1] by smtp105.bt.mail.ir2.yahoo.com with NNFMP; 03 May 2013 09:56:13 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=s1024; t=1367574973; bh=105FWvbje6Gr/TAdfLIVeE2QXbfeGfKQ/VYhBXbFp1E=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:X-Rocket-Received:Message-ID:From:To:References:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE:X-Antivirus:X-Antivirus-Status; b=Bbonx2Gn9N3Ofnhou2dhyesRwnNz3lH28W+/D+SXxwplq4mX2N5AYH4tj4HN2ykhQbalNLRRhWre1WaFujS5JMgI3+Judg/CNB/a8ygFHFBpKW+gnFI1ka34fh2KTYY7KU776rKGsPNDySwUksz3KHHgEqSoCFj2ENWAzp/6/m0= X-Yahoo-Newman-Id: 217483.5327.bm@smtp105.bt.mail.ir2.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: sN3vw00VM1m4phZw9KzkO0P4KS8MeO1qDiWbCNftqk6PVIs dSXR6Uz2Xwh8MDwSBtVfAZ21pX7G2Q7_s2K61fNR3b391QjVdJSFpym_h0lQ jqTF44lfxcRPVGOYvvr6HxQbgz2dBqZFLTyLG3IYAwWXzSe.liQ8VJVInq2S qQne1K2Dy5qDexL17r.x.yg3SrGOKWmfjsDVtLDP_noHmfTzUnowQFwx9RJ3 tCYVDbn3Qi.rvj8QQocfwcSkrAygjrYr6Uy11rWatN9.fojj.1NItAyLO.7g K.v3sciLhjn5Cynq5_P58KCDFIntKVembdKPlDMluTnoHjkjeMYHNK1OpmQI rIG.TiXm789cdmzTjfW2JwNU2dS41bQSy1mppUyLWLoBiQX2tHNkFskaMpwc MRL9t4pXsorHmHbgsVP2NANpRvDom6ydR3BupDrdE8Ms5hXRVclk2luTyBlk IaQnDq3yXMZ8- X-Yahoo-SMTP: fpz.2VeswBBs59bVshRPmMN51lcO2lgFRIvE4XTqE8dRwOxd70E- X-Rocket-Received: from gnat (alan.melia@86.167.13.182 with login) by smtp105.bt.mail.ir2.yahoo.com with SMTP; 03 May 2013 09:56:13 +0000 UTC Message-ID: From: "Alan Melia" To: References: <5182EB20.5000507@iup.uni-heidelberg.de> <73419E42F6C44E1EB1AB4FA0B2591817@SV8CSHP> <50100B1F0AB94D08B9E49C5DDB889EF3@White> Date: Fri, 3 May 2013 10:56:08 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Antivirus: avast! (VPS 130502-1, 02/05/2013), 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 Markus, Spiros, there is another interesting effect at dawn. The weak rays of the rising sun actually strike the ionoshere first from underneath !! this means that the first photodissociated ionisation is very highly absorbing because it is formed at lower levels where the pressure is higher and the electron mean-free-path is very short. This has the effect of producing a deep dip in levels at dawn at mid-path. That is dawn at an altitude of 50km or so, not ground level. This effect is most noticable on N<>S paths which I think is the direction of the grabbers from Spiros. [...] 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 [212.82.99.225 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: 9cafc73d135491d75f4f47d39ed43841 Subject: Re: LF: 136KHz propagation Content-Type: multipart/alternative; boundary="----=_NextPart_000_000B_01CE47EC.D0E47490" 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_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-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mtain-me02.r1000.mx.aol.com ; domain : btinternet.com DKIM : pass x-aol-sid: 3039ac1d608a518391cf7a07 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : temperror This is a multi-part message in MIME format. ------=_NextPart_000_000B_01CE47EC.D0E47490 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Hi Markus, Spiros, there is another interesting effect at dawn. The weak = rays of the rising sun actually strike the ionoshere first from = underneath !! this means that the first photodissociated ionisation is = very highly absorbing because it is formed at lower levels where the = pressure is higher and the electron mean-free-path is very short. This = has the effect of producing a deep dip in levels at dawn at mid-path. = That is dawn at an altitude of 50km or so, not ground level. This effect = is most noticable on N<>S paths which I think is the direction of the = grabbers from Spiros.=20 An hour or so later the Sun will have risen sufficiently to illuminate = the path from above and the daytime D-layer will build to provide = daytime skywave. The signal levels in daytime usually show a gentle = "dome" shape with the peak at mid-day at mid-path.=20 in the early days of 136kHz it was though that dawn would be a good time = for DX because the noise was lowest. However we eventually realised that = the noise was low because the distant noise which propagated by skywave = was wiped out at dawn by this effect. Thus the best DX times are often = (but not always :-)) ) early evening or about an hour before dawn. Great Fun this Propagation stuff :-)) Alan G3NYK ----- Original Message ----- =20 From: Markus Vester=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Friday, May 03, 2013 8:36 AM Subject: Re: LF: 136KHz propagation Hi Spiros, not really strange: the rising sun is suddenly ionizing lower = ionospheric layers and increasing the absorption.=20 Here's a somewhat simplistic explanation of diurnal propagation: At = night, LF is mostly reflected by the lower boundary of the E-layer, at a = height of about 100 km. After sunrise, radiations starts to penetrate = deeper and ionize lower layers. So the conductivity of the D-layer = increases so much that it starts first absorb and later reflect LF.=20 This is somewhat similar to a shunt resistor inserted in a = transmission line: During the night it's a large resistor which will let = most of the wave pass through, absorbing only a small fraction of the = power which depends on "conditions" (like DST index, describing charges = leaking down from a storage ring). At sunrise, the shunt suddenly = conducts more ("closer to 50 ohms") so most of the wave is being = absorbed. At midday when the sun is highest, the conductance is = approaching a "short circuit" which reflects the wave from a lower = altitude (about 80 km). After sunset, the electrons and ions in the lower layers recombine = quickly so the D-layer becomes transparent again. However at high = altitudes, the gas density is so low that charges take long to find a = partner, thus ionisation of the E and F layers persists throughout the = night.=20 Best 73, Markus (DF6NM) From: SV8CS- Spiros Chimarios=20 Sent: Friday, May 03, 2013 5:58 AM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: 136KHz propagation GM to all. The same strange propagation tonight as every night. At around 03.00z my signal disappear from DF6NM, DK7FC, YO/4X1RF & = G4WGT=20 grabbers. I have better prop earlier and during the day with day light. 73, Spiros SV8CS ------=_NextPart_000_000B_01CE47EC.D0E47490 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Hi Markus, Spiros, there is another = interesting=20 effect at dawn. The weak rays of the rising sun actually strike the = ionoshere=20 first from underneath !! this means that the first = photodissociated=20 ionisation is very highly absorbing because it is formed at lower levels = where=20 the pressure is higher and the electron mean-free-path is very short. = This has=20 the effect of producing a deep dip in levels at dawn at mid-path. That = is dawn=20 at an altitude of 50km or so, not ground level. This effect is most = noticable on=20 N<>S paths which I think is the direction of the grabbers from = Spiros.=20
 
An hour or so later the Sun will have = risen=20 sufficiently to illuminate the path from above and the daytime D-layer = will=20 build to provide daytime skywave. The signal levels in daytime usually = show a=20 gentle "dome" shape with the peak at mid-day at mid-path.
 
in the early days of 136kHz it was = though that dawn=20 would be a good time for DX because the noise was lowest. However we = eventually=20 realised that the noise was low because the distant noise which = propagated by=20 skywave was wiped out at dawn by this effect. Thus the best DX times are = often=20 (but not always :-))   )  early evening or about an hour = before=20 dawn.
 
Great Fun this Propagation stuff = :-))
 
Alan G3NYK
----- Original Message -----  =
From:=20 Markus=20 Vester
Sent: Friday, May 03, 2013 8:36 = AM
Subject: Re: LF: 136KHz = propagation

Hi Spiros,
 
not really = strange: the rising=20 sun is suddenly ionizing lower ionospheric layers and = increasing the=20 absorption. 
 
Here's a somewhat simplistic = explanation of=20 diurnal propagation: At night, LF is mostly reflected by the lower = boundary of=20 the E-layer, at a height of about 100 km. After sunrise, radiations = starts to=20 penetrate deeper and ionize lower layers. So = the conductivity of the=20 D-layer increases so much that it starts first absorb and = later reflect=20 LF. 
 
This is somewhat similar to a shunt=20 resistor inserted in a transmission line: During the = night it's=20 a large resistor which will let most of the wave pass through, = absorbing=20 only a small fraction of the power which depends on = "conditions" (like=20 DST index, describing charges leaking down from a storage ring).=20 At sunrise, the shunt=20 suddenly conducts more ("closer to 50 ohms") so most of the = wave is=20 being absorbed. At midday when the sun is highest, the = conductance=20 is approaching a "short circuit" which reflects the wave = from a=20 lower altitude (about 80 km).
 
After sunset, the electrons and ions = in the lower=20 layers recombine quickly so the D-layer becomes transparent again. = However at=20 high altitudes, the gas density is so low that charges = take=20 long to find a partner, thus ionisation of the E and F layers = persists=20 throughout the night. 
 
Best = 73,
Markus = (DF6NM)

Sent: Friday, May 03, 2013 5:58 AM
Subject: LF: 136KHz propagation

GM to all.
The same strange propagation tonight as = every=20 night.
At around 03.00z my signal disappear from DF6NM, DK7FC, = YO/4X1RF=20 & G4WGT
grabbers.
I have better prop earlier and during the = day=20 with day light.
73, = Spiros
SV8CS

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