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WJhZ.nLYqrA-- X-Yahoo-SMTP: fpz.2VeswBBs59bVshRPmMN51lcO2lgFRIvE4XTqE8dRwOxd70E- X-Rocket-Received: from gnat (alan.melia@86.167.13.182 with login) by smtp815.mail.ird.yahoo.com with SMTP; 08 May 2013 23:00:25 +0000 GMT Message-ID: From: "Alan Melia" To: References: <5182EB20.5000507@iup.uni-heidelberg.de> <73419E42F6C44E1EB1AB4FA0B2591817@SV8CSHP> <50100B1F0AB94D08B9E49C5DDB889EF3@White> Date: Thu, 9 May 2013 00:00:24 +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 130508-0, 08/05/2013), 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 again Markus the reference I gave for the Bob Brown article was the wrong one. The one I was meaning to give is the one published in QEX Jan/Feb 2001 pages 28-36 Alan G3NYK ----- Original Message ----- From: Markus Vester To: rsgb_lf_group@blacksheep.org Sent: Friday, May 03, 2013 6:14 PM Subject: Re: LF: 136KHz propagation [...] 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 [212.82.99.217 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: d7ba04df72d514a2ac46bed25e5ef7ca Subject: Re: LF: 136KHz propagation...new ref. Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01CE4C48.34CC8CE0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.4 required=5.0 tests=FORGED_MUA_OUTLOOK,HTML_30_40, 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-de06.r1000.mx.aol.com ; domain : btinternet.com DKIM : pass x-aol-sid: 3039ac1d40ce518ad9892e11 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_0006_01CE4C48.34CC8CE0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Hi again Markus the reference I gave for the Bob Brown article was the = wrong one. The one I was meaning to give is the one published in QEX = Jan/Feb 2001 pages 28-36 Alan G3NYK ----- Original Message -----=20 From: Markus Vester=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Friday, May 03, 2013 6:14 PM Subject: Re: LF: 136KHz propagation 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_0006_01CE4C48.34CC8CE0 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Hi again Markus the reference I gave = for the Bob=20 Brown article was the wrong one. The one I was meaning to give is the = one=20 published in QEX  Jan/Feb 2001 pages 28-36
 
Alan G3NYK
 
----- Original Message -----
From:=20 Markus=20 Vester
Sent: Friday, May 03, 2013 6:14 = PM
Subject: Re: LF: 136KHz = propagation

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=20 be that the ultraviolet radiation must have passed = the=20 same layer on the way down further east, at the same slant angle. = So far=20 my understanding has been that ionisation of different molecules=20 selectively takes out certain wavelengths. How can the D layer be = transparent=20 to a ray on 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=20 on N<>S paths which I think is the direction of the grabbers = from=20 Spiros.
 
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=20 dawn would be a good time for DX because the noise was lowest. However = we=20 eventually realised that the noise was low because the distant noise = which=20 propagated by skywave was wiped out at dawn by this effect. Thus the = best DX=20 times are often (but not always :-))   )  early evening = or=20 about an hour before dawn.
 
Great Fun this Propagation stuff=20 :-))
 
Alan G3NYK
----- Original Message -----  =
From:=20 Markus=20 Vester
To: rsgb_lf_group@blacksheep.org= =20
Sent: Friday, May 03, 2013 = 8:36=20 AM
Subject: Re: LF: 136KHz=20 propagation

Hi Spiros,
 
not really = strange: the rising=20 sun is suddenly ionizing lower ionospheric layers and = increasing=20 the absorption. 
 
Here's a somewhat simplistic = explanation of=20 diurnal propagation: At night, LF is mostly reflected by the lower = boundary=20 of the E-layer, at a height of about 100 km. After sunrise, = radiation starts=20 to penetrate deeper and ionize lower layers. So = the conductivity=20 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=20 a large resistor which will let most of the wave pass through,=20 absorbing only a small fraction of the power which depends on=20 "conditions" (like DST index, describing charges = leaking down from=20 a storage ring). At=20 sunrise, the shunt suddenly conducts = more ("closer to 50=20 ohms") so most of the wave is being absorbed. At midday when the sun = is=20 highest, the conductance is approaching a "short circuit" = which=20 reflects the wave from a lower altitude (about 80=20 km).
 
After sunset, the electrons and = ions in the=20 lower layers recombine quickly so the D-layer becomes transparent = again.=20 However at high altitudes, the gas density is so low=20 that charges take long to find a partner, thus ionisation = of the E=20 and F layers persists 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,=20 Spiros
SV8CS

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