Return-Path: Received: from mtain-dh08.r1000.mx.aol.com (mtain-dh08.r1000.mx.aol.com [172.29.65.28]) by air-da05.mail.aol.com (v127_r1.1) with ESMTP id MAILINDA051-85e74b93842a38c; Sun, 07 Mar 2010 05:47:06 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dh08.r1000.mx.aol.com (Internet Inbound) with ESMTP id DCBDA3800008E; Sun, 7 Mar 2010 05:47:04 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NoDzF-0004G8-N4 for rs_out_1@blacksheep.org; Sun, 07 Mar 2010 10:45:29 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NoDzE-0004Fz-Rn for rsgb_lf_group@blacksheep.org; Sun, 07 Mar 2010 10:45:28 +0000 Received: from mailout05.t-online.de ([194.25.134.82]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NoDzC-0002vc-9m for rsgb_lf_group@blacksheep.org; Sun, 07 Mar 2010 10:45:28 +0000 Received: from fwd08.aul.t-online.de (fwd08.aul.t-online.de ) by mailout05.t-online.de with smtp id 1NoDz9-0004qx-DG; Sun, 07 Mar 2010 11:45:23 +0100 Received: from e7010 (SgCTpcZDYhqDl3aqaS2Btk5qouofbzZx7zKt+t0ZSUiNmdxKzWcc+tgHE1uV9jowGv@[84.147.226.115]) by fwd08.aul.t-online.de with smtp id 1NoDyu-0dfiTY0; Sun, 7 Mar 2010 11:45:08 +0100 Message-ID: <004401cabde3$4c60d240$6402a8c0@e7010> From: "Walter und Marianne Staubach" To: References: <2CDE578A1E1B49AF96D61BB5D91FA03D@White> Date: Sun, 7 Mar 2010 11:45:21 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4927.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4927.1200 X-ID: SgCTpcZDYhqDl3aqaS2Btk5qouofbzZx7zKt+t0ZSUiNmdxKzWcc+tgHE1uV9jowGv X-TOI-MSGID: 31c7e636-83a0-4ce4-9d72-ca4870ad58c1 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,UNPARSEABLE_RELAY=0.001 Subject: LF: Re: 12 km on Dream(ers) Band Content-Type: multipart/alternative; boundary="----=_NextPart_000_0041_01CABDEB.AAE77460" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=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-sid: 3039ac1d411c4b938428123c X-AOL-IP: 193.82.116.20 ------=_NextPart_000_0041_01CABDEB.AAE77460 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Lieber Markus, herzlichen Gl=FCckwunsch zu Deinem 12,1Km-Erfolg. R=FCckt da= nicht ein QSO zwischen uns in greifbare N=E4he?=20 Ein gl=FCcklicher Zufall spielte mir eine VLF-Drossel in die H=E4nde,= 18mH in 10 Einzelspulen auf Abstand. In das Pertinax-R=F6hrchen l=E4s= st sich ein Ferritstab schieben. Mit einem Drehko 1000pf komme ich bis= ca. 8KHz herunter. Dies vor dem VLF-Konverter geht recht gut. F=FCr die Sendeseite ist das allerdings nicht ausreichend sp= annungsfest. 73 Walter ----- Original Message -----=20 From: Markus Vester=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Saturday, March 06, 2010 9:16 PM Subject: LF: 12 km on Dream(ers) Band Dear LF, =20 on two evenings this week, I have transmitted an 8.97 kHz signal fro= m my LF Marconi at home, and attempted to receive it at various locati= ons. The experiment was very similar to the one in April 2003, but wit= h a moderate improvement in ERP and FFT bandwidth. Now on both occasio= ns, the carrier could be detected at a distance of 12.1 km: http://www= .mydarc.de/df6nm/vlf/vlf_12km.jpg =20 My transmit antenna is relatively small, about 220 pF and 9 m effect= ive height at 137 kHz. Assuming a 20% reduction due to shielding, radi= ation resistance would be around 74 microohms at 9 kHz. The 1.4 henry= loading coil is about 30 cm long by 12 cm diameter, and is split into= seven slightly conical sections, partly inserted into one another (ht= tp://www.mydarc.de/df6nm/vlf/9kHz_aircoil.jpg). Each section has 700= turns of 0.2 mm enameled wire, total DC resistance is 830 ohms. Fine= tuning is achieved by shifting a thick block of ferrite into the last= section. Using a 35 W car-radio audio amplifier and a 1:32 ferrite tr= ansformer, I now got up to 0.135 A and 11 kV rms at the antenna. Radia= ted power was thus approximately 1.3 uW (EMRP). =20 I used the same 6 m portable receive antenna with series inductor as= before. I tried connecting directly to the microphone input of the ne= tbook computer, and also inserting a simple bipolar preamplifier, whic= h was fed from the 2.5 VDC present at the mic jack. Both versions turn= ed out to have almost the same sensitivity, but resonance peaking was= less critical with the transistor. Postprocessing was now done using= SpecLab, with software noise blanking, and either 15 mHz or 3.8 mHz= FFT bin width. SNR at 12.1 km was somewhere around 5 dB in 1.5x 3.8= mHz. With an expected signal of 0.9 uV/m there, this would imply a no= ise level on the order of 16 dBuV/m/sqrtHz. However on the last receiv= e site at 15.4 km, no trace of the signal could be retrieved. =20 The lowest of the Alpha navigation frequencies was included in the= decimated frequency range to check soundcard drift. Due to the repeat= ing dashes, the beacon spectrum is split into several lines 1/3.6 Hz= apart. The true center frequency (16*15625/21 =3D 11904.762 Hz) is on= e of the weaker lines here. But this depends on the relative phases of= the two strongest stations, and will be different in other areas. =20 The reception could possibly be a new amateur VLF distance record.= However with all the ongoing activity, I expect (and actually hope ;-= ) it won't last long... =20 Best wishes, Markus (DF6NM) =20 _______________________________________ Von: "Markus Vester" An: Betreff: LF: Re: 9kHz noise level Datum: Sonntag, 28. Februar 2010 14:06 =20 Dear Alexander, LF, =20 the frequency rulers of the modified Argo are actually correct, and= you can see how I reduced the bandwidth when going further away. The= minimum setting was 90 second dots, giving 0.042 Hz FFT resolution wh= en running at 4x normal samplerate (ie. 0.063 Hz noise BW) . =20 The marginal "T" trace at 6 km was probably no more than 0 dB SNR.= Thus the noise level (including spherics) would have been on the orde= r of 15 dBuV/m/sqrtHz. =20 Best 73, Markus, DF6NM =20 _______________________________________ Von: "Markus Vester" An: Betreff: LF: Re: 9kHz noise level Datum: Samstag, 27. Februar 2010 23:11 =20 Dear Jim, LF, =20 yes I'm aware of the fact that the shielding from trees etc is more= significant at lower frequency. Their ohmic conductance becomes a bet= ter shunt in comparison with decreasing capacitive admittance, somewha= t similar to a C-R highpass equivalent circuit. There used to be two= beautiful 15 m high fir trees in the vicinity of our house. At 137 kH= z, I measured a ~ 15% increase in effective height when the trees were= deeply frozen, but the effect on 9 kHz may have been more severe. A= couple of years ago our neighbours had these trees chopped down, good= for LF but otherwise sad. =20 In April 2003, I attempted to transmitt an 8.97 kHz carrier, radiati= ng about 1 microwatt from my normal LF antenna (220 pF at ~ 9m eff. he= ight). I drove around and stopped in different places, putting up a 6m= fishing pole with a wire, connected to a resonant circuit and the lap= top soundcard. Each time I took a short Spectrogram full-band screensh= ot, along with a narrowband capture from a special Argo version, patch= ed for 22 kHz samplerate. An assembly of the screenshots is at http:/= /freenet-homepage.de/df6nm/8970_ALL.gif. Maximum detection range was= 6 km, just marginally outside the reactive nearfield. No noiseblankin= g was attempted at the time. =20 If you look at the Spectrogram strips, you can see that the first (1= .6 km) and third (6.0 km) images have a much lower absolute receive le= vel. At first I thought something was wrong with the receive antenna,= until I realized that this was purely due to these sites being in a= forested area. =20 I have now rigged up SpecLab again for VLF reception. The Russian Al= pha beacons seem to be usefiul calibration markers, the nearest one is= currently about 20 dB SNR here in a 42 Hz FFT. Does anybody in the gr= oup have information about their EMRP, or has someone attempted to mea= sure their fieldstrength in Europe? =20 Best 73, Markus (DF6NM) =20 ------=_NextPart_000_0041_01CABDEB.AAE77460 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Lieber Markus,
      = ;    herzlichen=20 Gl=FCckwunsch zu Deinem 12,1Km-Erfolg. R=FCckt da nicht ein QSO zwisch= en uns in=20 greifbare N=E4he? 
Ein gl=FCcklicher Zufall spielte mir= eine VLF-Drossel=20 in die H=E4nde, 18mH in 10 Einzelspulen auf Abstand. In das Pertinax-R= =F6hrchen=20 l=E4sst sich ein Ferritstab schieben. Mit einem Drehko 1000pf komme ic= h bis ca.=20 8KHz herunter. Dies vor dem VLF-Konverter geht recht gut.
      = ;    F=FCr die Sendeseite ist=20 das allerdings nicht ausreichend spannungsfest.
73     Walter
 
----- Original Message -----
Sent: Saturday, March 06, 201= 0 9:16=20 PM
Subject: LF: 12 km on Dream(e= rs)=20 Band

Dear LF,
 
on two evenings this week, I have= transmitted an=20 8.97 kHz signal from my LF Marconi at home, and attempted to receive= it at=20 various locations. The experiment was very similar to the one in Apr= il 2003,=20 but with a moderate improvement in ERP and FFT bandwidth. Now on bot= h=20 occasions, the carrier could be detected at a distance of 12.1 km:&n= bsp;http:/= /www.mydarc.de/df6nm/vlf/vlf_12km.jpg
 
My transmit antenna is relatively= small, about=20 220 pF and 9 m effective height at 137 kHz. Assuming a 20% reduction= due to=20 shielding, radiation resistance would be around 74 microohms at 9 kH= z. The 1.4=20 henry loading coil is about 30 cm long by 12 cm diameter, and is spl= it into=20 seven slightly conical sections, partly inserted into one another (<= A href=3D"http://www.mydarc.de/df6nm/vlf/9kHz_aircoil.jpg" tit= le=3D"http://www.mydarc.de/df6nm/vlf/9kHz_aircoil.jpg STRG + Klick= en, um Verkn=FCpfung zu folgen">http://www.mydarc.de/df6nm/vlf/9kHz_ai= rcoil.jpg).=20 Each section has 700 turns of 0.2 mm enameled wire, total DC resista= nce is 830=20 ohms. Fine tuning is achieved by shifting a thick block of ferrite= into the=20 last section. Using a 35 W car-radio audio amplifier and a 1:32 ferr= ite=20 transformer, I now got up to 0.135 A and 11 kV rms at the antenna.= Radiated=20 power was thus approximately 1.3 uW (EMRP).
 
I used the same 6 m portable receiv= e antenna with=20 series inductor as before. I tried connecting directly to the microp= hone input=20 of the netbook computer, and also inserting a simple bipolar preampl= ifier,=20 which was fed from the 2.5 VDC present at the mic jack. Both version= s turned=20 out to have almost the same sensitivity, but resonance peaking was= less=20 critical with the transistor. Postprocessing was now done using Spec= Lab, with=20 software noise blanking, and either 15 mHz or 3.8 mHz FFT bin width.= SNR at=20 12.1 km was somewhere around 5 dB in 1.5x 3.8 mHz. With an expected= signal of=20 0.9 uV/m there, this would imply a noise level on the order of 16=20 dBuV/m/sqrtHz. However on the last receive site at 15.4 km, no trace= of the=20 signal could be retrieved.
 
The lowest of the Alpha navigation= frequencies=20 was included in the decimated frequency range to check soundcard dri= ft. Due to=20 the repeating dashes, the beacon spectrum is split into several line= s 1/3.6 Hz=20 apart. The true center frequency (16*15625/21 =3D 11904.762 Hz) is= one of the=20 weaker lines here. But this depends on the relative phases of the tw= o=20 strongest stations, and will be different in other areas.
 
The reception could possibly be a= new amateur VLF=20 distance record. However with all the ongoing activity, I expect (an= d actually=20 hope ;-) it won't last long...
 
Best wishes,
Markus (DF6NM)
 
___________________________________= ____
Von:=20 "Markus Vester" <mark= usvester@aol.com>
An: <rsgb_lf_group@blacksheep.org>
Betreff:=20 LF: Re: 9kHz noise level
Datum: Sonntag, 28. Februar 2010=20 14:06
 
Dear Alexander, LF,
 
the frequency rulers of the modifie= d Argo are=20 actually correct, and you can see how I reduced the bandwidth when= going=20 further away. The minimum setting was 90 second dots, giving 0.042= Hz FFT=20 resolution when running at 4x normal samplerate (ie. 0.063 Hz noise= BW)=20 .
 
The marginal "T" trace at 6 km was= probably no=20 more than 0 dB SNR. Thus the noise level (including spherics) would= have been=20 on the order of 15 dBuV/m/sqrtHz.
 
Best 73,
Markus, DF6NM
 
___________________________________= ____
Von:=20 "Markus Vester" <mark= usvester@aol.com>
An: <rsgb_lf_group@blacksheep.org>
Betreff:=20 LF: Re: 9kHz noise level
Datum: Samstag, 27. Februar 2010=20 23:11
 
Dear Jim, LF,
 
yes I'm aware of the fact that the= shielding from=20 trees etc is more significant at lower frequency. Their ohmic conduc= tance=20 becomes a better shunt in comparison with decreasing capacitive admi= ttance,=20 somewhat similar to a C-R highpass equivalent circuit. There used to= be two=20 beautiful 15 m high fir trees in the vicinity of our house. At 137= kHz, I=20 measured a ~ 15% increase in effective height when the trees were de= eply=20 frozen, but the effect on 9 kHz may have been more severe. A couple= of years=20 ago our neighbours had these trees chopped down, good for LF but oth= erwise=20 sad.
 
In April 2003, I attempted to trans= mitt an 8.97=20 kHz carrier, radiating about 1 microwatt from my normal LF antenna= (220 pF at=20 ~ 9m eff. height). I drove around and stopped in different places,= putting up=20 a 6m fishing pole with a wire, connected to a resonant circuit and= the laptop=20 soundcard. Each time I took a short Spectrogram full-band screenshot= , along=20 with a narrowband capture from a special Argo version, patched for= 22 kHz=20 samplerate. An assembly of the screenshots is at  http://freenet-home= page.de/df6nm/8970_ALL.gif.=20 Maximum detection range was 6 km, just marginally outside the reacti= ve=20 nearfield. No noiseblanking was attempted at the time.
 
If you look at the Spectrogram stri= ps, you can=20 see that the first (1.6 km) and third (6.0 km) images have a much lo= wer=20 absolute receive level. At first I thought something was wrong with= the=20 receive antenna, until I realized that this was purely due to these= sites=20 being in a forested area.
 
I have now rigged up SpecLab again= for VLF=20 reception. The Russian Alpha beacons seem to be usefiul calibration= markers,=20 the nearest one is currently about 20 dB SNR here in a 42 Hz FFT. Do= es anybody=20 in the group have information about their EMRP, or has someone attem= pted to=20 measure their fieldstrength in Europe?
 
Best 73,
Markus (DF6NM)
 
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