Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-de01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 31B863800009B; Fri, 3 May 2013 13:16:35 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UYJZc-0000pM-PX for rs_out_1@blacksheep.org; Fri, 03 May 2013 18:15:08 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UYJZc-0000pD-4a for rsgb_lf_group@blacksheep.org; Fri, 03 May 2013 18:15:08 +0100 Received: from omr-m10.mx.aol.com ([64.12.143.86]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1UYJZZ-0004Nz-Gw for rsgb_lf_group@blacksheep.org; Fri, 03 May 2013 18:15:07 +0100 Received: from mtaout-da03.r1000.mx.aol.com (mtaout-da03.r1000.mx.aol.com [172.29.51.131]) by omr-m10.mx.aol.com (Outbound Mail Relay) with ESMTP id 6BBA6700000B0 for ; Fri, 3 May 2013 13:14:42 -0400 (EDT) Received: from White (188-195-246-26-dynip.superkabel.de [188.195.246.26]) by mtaout-da03.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 4EA2BE0000E3 for ; Fri, 3 May 2013 13:14:39 -0400 (EDT) Message-ID: From: "Markus Vester" To: References: <5182EB20.5000507@iup.uni-heidelberg.de> <73419E42F6C44E1EB1AB4FA0B2591817@SV8CSHP> <50100B1F0AB94D08B9E49C5DDB889EF3@White> Date: Fri, 3 May 2013 19:14:05 +0200 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 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1367601282; bh=oYVLoogpsLq1+/5GFTc6Vp+C/EzFTvgbrsZ+xLuvSX0=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=cAdlaTfcmWYd6+AgaRxWJIqQimRqDQ6GfcU9Zyeir9BhO3LF8L+4BVvp34LLymYcY 8/dnz+iWzR9Hi2T6zEkIP4+YYH/2IaAf1OP/LYQGyQPBchJyaeGkRl4pvXvtEZcRs5 2suPu1dWLuQ7ipxuN0p9JhieDCtRuTsaUl/JJs7Y= X-AOL-SCOLL-SCORE: 0:2:317602144:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-Spam-Score: -2.6 (--) 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 Alan, the morning light shining from underneath is an intruiging notion, and I've been wondering about it since you first mentioned it a while ago. To me, one conceptual problem seems to be that the ultraviolet radiation must have passed the same layer on the way down further east, at the same slant angle. So far my understanding has been that ionisation of different molecules selectively takes out certain wavelengths. How can the D layer be transparent to a ray on the way down, and then opaque on the way up? [...] Content analysis details: (-2.6 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [64.12.143.86 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 SPF_PASS SPF: sender matches SPF record -2.6 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 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: 7117f452ff11af9bac782a916713f0d7 Subject: Re: LF: 136KHz propagation Content-Type: multipart/alternative; boundary="----=_NextPart_000_0008_01CE4832.61131BD0" 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-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mtain-de01.r1000.mx.aol.com ; domain : mx.aol.com DKIM : pass x-aol-sid: 3039ac1d40c95183f0f356fa X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Dies ist eine mehrteilige Nachricht im MIME-Format. ------=_NextPart_000_0008_01CE4832.61131BD0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Hi Alan,=20 the morning light shining from underneath is an intruiging notion, and = I've been wondering about it since you first mentioned it a while ago.=20 To me, one conceptual problem seems to be that the ultraviolet radiation = must have passed the same layer on the way down further east, at the = same slant angle. So far my understanding has been that ionisation of = different molecules selectively takes out certain wavelengths. How can = the D layer be transparent to a ray on the way down, and then opaque on = the way up? Best 73, Markus (DF6NM) From: Alan Melia=20 Sent: Friday, May 03, 2013 11:56 AM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: 136KHz propagation 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, radiation starts to penetrate = deeper and ionize lower layers. So the conductivity of the D-layer = increases so much that it starts to first absorb, and later reflect, LF. = 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_0008_01CE4832.61131BD0 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Hi Alan,
 
the morning light shining from = underneath is an=20 intruiging notion, and I've been wondering about = it since you=20 first mentioned it a while ago. 
 
To me, one conceptual = problem seems to be=20 that the ultraviolet radiation must have passed the = same=20 layer on the way down further east, at the same slant angle. So far = my=20 understanding has been that ionisation of different molecules = selectively=20 takes out certain wavelengths. How can the D layer be transparent to a = ray on=20 the way down, and then opaque on the way up?
 
Best 73,
Markus (DF6NM)

From: Alan Melia
Sent: Friday, May 03, 2013 11:56 AM
Subject: Re: LF: 136KHz propagation

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, radiation = starts to=20 penetrate deeper and ionize lower layers. So = the conductivity of the=20 D-layer increases so much that it starts to first absorb, and=20 later reflect, 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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