Return-Path: Received: from mtain-dc01.r1000.mx.aol.com (mtain-dc01.r1000.mx.aol.com [172.29.64.129]) by air-df06.mail.aol.com (v127_r1.1) with ESMTP id MAILINDF063-5ef84b9ec03b33; Mon, 15 Mar 2010 19:18:19 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dc01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 5DC34380000C5; Mon, 15 Mar 2010 19:18:17 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NrJTJ-0000WJ-ST for rs_out_1@blacksheep.org; Mon, 15 Mar 2010 23:13:17 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NrJTJ-0000WA-CT for rsgb_lf_group@blacksheep.org; Mon, 15 Mar 2010 23:13:17 +0000 Received: from imr-da01.mx.aol.com ([205.188.105.143]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NrJTG-0006mU-BT for rsgb_lf_group@blacksheep.org; Mon, 15 Mar 2010 23:13:17 +0000 Received: from mtaout-mb01.r1000.mx.aol.com (mtaout-mb01.r1000.mx.aol.com [172.29.41.65]) by imr-da01.mx.aol.com (8.14.1/8.14.1) with ESMTP id o2FND0l1017883 for ; Mon, 15 Mar 2010 19:13:00 -0400 Received: from Black (g229121179.adsl.alicedsl.de [92.229.121.179]) by mtaout-mb01.r1000.mx.aol.com (WebSuites/MUA Thirdparty client Interface) with ESMTPA id B0A9FE000101 for ; Mon, 15 Mar 2010 19:12:59 -0400 (EDT) Message-ID: From: "Markus Vester" To: References: In-Reply-To: Date: Tue, 16 Mar 2010 00:12:14 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6000.16480 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6000.16669 x-aol-global-disposition: G x-aol-sid: 3039ac1d29414b9ebefb132d X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Ionospheric VLF propagation Content-Type: multipart/alternative; boundary="----=_NextPart_000_007A_01CAC49D.551353C0" 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_20_30,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: 3039ac1d40814b9ec0391d72 X-AOL-IP: 193.82.116.20 ------=_NextPart_000_007A_01CAC49D.551353C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dear LF, on the phone, Stefan mentioned that he was running about 0.4 A into th= e nearly vertical (70=B0), 100 m long kite antenna. Thus radiated powe= r would be=20 EMRP =3D 1579 ohm * (0.4 A * sin(70=B0) * 50 m / 33 km)^2 =3D 0.5 mW= =3D -3 dBm. Using 1/distance field decay above lossless flat earth, at 830 km we= would expect a field strength E =3D -3 + 49.5 - 20 log (830) dBuV/m =3D -12 dBuV/m. However Paul's calibrated spectrum at 14:38 UT showed a peak B =3D 3.1= fT at 8970 Hz, equivalent to an electrical field E =3D c * B =3D 0.93 uV/m =3D - 0.5 dBuV/m. Taking into account a couple of dB's for measurement uncertainties, we= are still left with an observed signal very significantly stronger th= an expected. This seems to support Alexander's statement about a slowe= r than inverse distance decay in the two-dimensional ionosphere-earth= waveguide. On http://freenet-homepage.de/df6nm/vlf/vlf_DHO_dualfreq.htm , I have= another observation pointing out an ionospheric effect on VLF. In 200= 6, the German naval transmitter DHO38, normally on 23.4 kHz, was simul= taneously transmitting on 18.5 kHz as well. Surprisingly the fieldstre= ngths and the diurnal patterns for the two frequencies appeared to be= completely different, presumably due to different phaseshifts between= ground and skywave component. Best regards, MArkus (DF6NM) ----- Original Message -----=20 From: Alexander S. Yurkov=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, February 25, 2010 6:53 PM Subject: Re: LF: AW: 9 Dreamers Hellow, Stefan. > If that calculation is reasonably correct, what distance could be= =20 > reached with 1,4mW @ 8,9 kHz=20 With such a condition you'll get about 2.5 uV/m at 100 km. Seems it= can be recievid. If there is no atmospheric and industrial noise it should= be very strong signal. But all depends on noise on 9 kHz. I have no ide= as about noise on 9 kHz. I neglet ionosphere in estimations. But at D= =3D100 km it should be approximately right.=20 Anyway if you can use 100 m high antenna then few of 100's km you sh= ould reach. May be substantionally more. For large distances dependance= of E on D changes. On the distances more then ~100 km field should have behaviour E ~ sqrt(1/D). This yelds only 10 dB attenuation if distan= ce became 10 times more. Thus if you'll have 20 dB over noise at 100 km= (if noise is 0.25 uV/m for example) then you'll have ~10 dB over noise= at 1000 km. =20 Do it if you have such an oportunity! It is very interesting. Regards, Alexander ------=_NextPart_000_007A_01CAC49D.551353C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Dear LF,
 
on the phone, Stefan mentioned that= he was running=20 about 0.4 A into the nearly vertical (70=B0), 100 m long kit= e=20 antenna. Thus radiated power would be
 
 EMRP =3D 1579 ohm *= (0.4 A * sin(70=B0)=20 * 50 m / 33 km)^2 =3D 0.5 mW =3D -3 dBm.
 
Using 1/distance field decay above lo= ssless flat=20 earth, at 830 km we would expect a field strength
 
 E =3D -3 + 49.5 - 20 log (830)= dBuV/m =3D -12=20 dBuV/m.
 
However Paul's calibrated spectrum at= 14:38 UT=20 showed a peak B =3D 3.1 fT at 8970 Hz, equivalent to an elec= trical=20 field
 
 E =3D c * B =3D 0.93 uV/m =3D= - 0.5=20 dBuV/m.
 
Taking into account a couple of= dB's=20 for measurement uncertainties, we are still left with an observed= signal=20 very significantly stronger than expected. This seems to support Alexander's statement&n= bsp;about a slower=20 than inverse distance decay in the two-dimensional ionospher= e-earth=20 waveguide.
 
On <= A href=3D"http://freenet-homepage.de/df6nm/vlf/vlf_DHO_dualfreq.htm"= >http://freenet-homepage.de/df6nm/vlf/vlf_DHO_dualfreq.htm= =20 , I have another observation pointing out an ionospheri= c effect=20 on VLF. In 2006, the German naval transmitter DHO38, normall= y on 23.4=20 kHz, was simultaneously transmitting on 18.5 kHz as=20 well. Surprisingly the fieldstrengths and the diurnal patterns fo= r the two=20 frequencies appeared to be completely different, presumably due= to=20 different phaseshifts between ground and skywave component.
 
Best regards,
MArkus (DF6NM)
 
----- Original Message -----
Sent: Thursday, February 25,= 2010 6:53=20 PM
Subject: Re: LF: AW: 9 Dreame= rs
=
Hellow, Stefan= .

> If that=20 calculation is reasonably correct, what distance could be
>= reached=20 with 1,4mW @ 8,9 kHz

With such a condition you'll get about= 2.5 uV/m=20 at 100 km. Seems it can be
recievid. If there is no atmospheric= and=20 industrial noise it should be
very strong signal. But all depends= on noise=20 on 9 kHz. I have no ideas
about noise on 9 kHz. I neglet ionosphe= re in=20 estimations. But at D=3D100 km
it should be approximately right.= =20

Anyway if you can use 100 m high antenna then few of 100's= km you=20 should
reach. May be substantionally more. For large distances de= pendance=20 of E
on D changes. On the distances more then ~100 km field shoul= d=20 have
behaviour E ~ sqrt(1/D). This yelds only 10 dB attenuation= if=20 distance
became 10 times more. Thus if you'll have 20 dB over noi= se at 100=20 km (if
noise is 0.25 uV/m for example) then you'll have ~10 dB ov= er noise=20 at 1000
km. 

Do it if you have such an oportunity!= It is very=20 interesting.

Regards,
Alexander
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