Return-Path: Received: from mtain-mg07.r1000.mx.aol.com (mtain-mg07.r1000.mx.aol.com [172.29.96.207]) by air-mc05.mail.aol.com (v127_r1.1) with ESMTP id MAILINMC053-a9694b92b88a234; Sat, 06 Mar 2010 15:18:18 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mg07.r1000.mx.aol.com (Internet Inbound) with ESMTP id 93C4C3800009B; Sat, 6 Mar 2010 15:18:16 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1No0Qv-0001B6-So for rs_out_1@blacksheep.org; Sat, 06 Mar 2010 20:17:09 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1No0Qv-0001Ax-12 for rsgb_lf_group@blacksheep.org; Sat, 06 Mar 2010 20:17:09 +0000 Received: from imr-da02.mx.aol.com ([205.188.105.144]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1No0Qr-0002J5-IB for rsgb_lf_group@blacksheep.org; Sat, 06 Mar 2010 20:17:08 +0000 Received: from mtaout-mb01.r1000.mx.aol.com (mtaout-mb01.r1000.mx.aol.com [172.29.41.65]) by imr-da02.mx.aol.com (8.14.1/8.14.1) with ESMTP id o26KGr6C017455 for ; Sat, 6 Mar 2010 15:16:53 -0500 Received: from White (g229248221.adsl.alicedsl.de [92.229.248.221]) by mtaout-mb01.r1000.mx.aol.com (WebSuites/MUA Thirdparty client Interface) with ESMTPA id 32C1CE000089 for ; Sat, 6 Mar 2010 15:16:50 -0500 (EST) Message-ID: <2CDE578A1E1B49AF96D61BB5D91FA03D@White> From: "Markus Vester" To: Date: Sat, 6 Mar 2010 21:16:47 +0100 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d29414b92b8324d8c X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: 12 km on Dream(ers) Band Content-Type: multipart/alternative; boundary="----=_NextPart_000_000F_01CABD72.545DDF40" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=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: 3039ac1d60cf4b92b88844e4 X-AOL-IP: 193.82.116.20 ------=_NextPart_000_000F_01CABD72.545DDF40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dear LF, on two evenings this week, I have transmitted an 8.97 kHz signal from= my LF Marconi at home, and attempted to receive it at various locatio= ns. The experiment was very similar to the one in April 2003, but with= a moderate improvement in ERP and FFT bandwidth. Now on both occasion= s, the carrier could be detected at a distance of 12.1 km: http://www.= mydarc.de/df6nm/vlf/vlf_12km.jpg My transmit antenna is relatively small, about 220 pF and 9 m effectiv= e height at 137 kHz. Assuming a 20% reduction due to shielding, radiat= ion resistance would be around 74 microohms at 9 kHz. The 1.4 henry lo= ading coil is about 30 cm long by 12 cm diameter, and is split into se= ven slightly conical sections, partly inserted into one another (http:= //www.mydarc.de/df6nm/vlf/9kHz_aircoil.jpg). Each section has 700 turn= s of 0.2 mm enameled wire, total DC resistance is 830 ohms. Fine tunin= g is achieved by shifting a thick block of ferrite into the last secti= on. Using a 35 W car-radio audio amplifier and a 1:32 ferrite transfor= mer, I now got up to 0.135 A and 11 kV rms at the antenna. Radiated po= wer was thus approximately 1.3 uW (EMRP). 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. The lowest of the Alpha navigation frequencies was included in the dec= imated frequency range to check soundcard drift. Due to the repeating= dashes, the beacon spectrum is split into several lines 1/3.6 Hz apar= t. The true center frequency (16*15625/21 =3D 11904.762 Hz) is one of= the weaker lines here. But this depends on the relative phases of the= two strongest stations, and will be different in other areas. The reception could possibly be a new amateur VLF distance record. How= ever with all the ongoing activity, I expect (and actually hope ;-) it= won't last long... Best wishes, Markus (DF6NM) _______________________________________ Von: "Markus Vester" An: Betreff: LF: Re: 9kHz noise level Datum: Sonntag, 28. Februar 2010 14:06 Dear Alexander, LF, the frequency rulers of the modified Argo are actually correct, and yo= u can see how I reduced the bandwidth when going further away. The min= imum setting was 90 second dots, giving 0.042 Hz FFT resolution when= running at 4x normal samplerate (ie. 0.063 Hz noise BW) . The marginal "T" trace at 6 km was probably no more than 0 dB SNR. Thu= s the noise level (including spherics) would have been on the order of= 15 dBuV/m/sqrtHz. Best 73, Markus, DF6NM _______________________________________ Von: "Markus Vester" An: Betreff: LF: Re: 9kHz noise level Datum: Samstag, 27. Februar 2010 23:11 Dear Jim, LF, yes I'm aware of the fact that the shielding from trees etc is more si= gnificant at lower frequency. Their ohmic conductance becomes a better= shunt in comparison with decreasing capacitive admittance, somewhat= similar to a C-R highpass equivalent circuit. There used to be two be= autiful 15 m high fir trees in the vicinity of our house. At 137 kHz,= 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. In April 2003, I attempted to transmitt an 8.97 kHz carrier, radiating= about 1 microwatt from my normal LF antenna (220 pF at ~ 9m eff. heig= ht). 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. 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 leve= l. At first I thought something was wrong with the receive antenna, un= til I realized that this was purely due to these sites being in a fore= sted area. I have now rigged up SpecLab again for VLF reception. The Russian Alph= a 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? Best 73, Markus (DF6NM) ------=_NextPart_000_000F_01CABD72.545DDF40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Dear LF,
 
on two evenings this week, I have tra= nsmitted 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 April= 2003, but=20 with a moderate improvement in ERP and FFT bandwidth. Now on both occa= sions, the=20 carrier could be detected at a distance of 12.1 km: http://www.mydarc.de/df6n= m/vlf/vlf_12km.jpg
 
My transmit antenna is relatively sma= ll, about 220=20 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 kHz.= The 1.4=20 henry loading coil is about 30 cm long by 12 cm diameter, and is split= into=20 seven slightly conical sections, partly inserted into one another (http://www.mydarc.de/df6nm/vlf/9kHz_airco= il.jpg).=20 Each section has 700 turns of 0.2 mm enameled wire, total DC resistanc= e is 830=20 ohms. Fine tuning is achieved by shifting a thick block of ferrite int= o the last=20 section. Using a 35 W car-radio audio amplifier and a 1:32 ferrite tra= nsformer,=20 I now got up to 0.135 A and 11 kV rms at the antenna. Radiated power= was thus=20 approximately 1.3 uW (EMRP).
 
I used the same 6 m portable receive= antenna with=20 series inductor as before. I tried connecting directly to the micropho= ne input=20 of the netbook computer, and also inserting a simple bipolar preamplif= ier, which=20 was fed from the 2.5 VDC present at the mic jack. Both versions turned= out to=20 have almost the same sensitivity, but resonance peaking was less criti= cal with=20 the transistor. Postprocessing was now done using SpecLab, with softwa= re noise=20 blanking, and either 15 mHz or 3.8 mHz FFT bin width. SNR at 12.1 km= was=20 somewhere around 5 dB in 1.5x 3.8 mHz. With an expected signal of 0.9= uV/m=20 there, this would imply a noise level on the order of 16 dBuV/m/sqrtHz= . However=20 on the last receive site at 15.4 km, no trace of the signal could be= =20 retrieved.
 
The lowest of the Alpha navigation fr= equencies was=20 included in the decimated frequency range to check soundcard drift. Du= e to the=20 repeating dashes, the beacon spectrum is split into several lines 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 two= strongest=20 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 (and= actually=20 hope ;-) it won't last long...
 
Best wishes,
Markus (DF6NM)=
 
_____________________________________= __
Von:=20 "Markus Vester" <markusve= ster@aol.com>
An: <rsgb_lf_group@blacksheep.org>
Betreff:=20 LF: Re: 9kHz noise level
Datum: Sonntag, 28. Februar 2010 14:06
 
Dear Alexander, LF,
 
the frequency rulers of the modified= Argo are=20 actually correct, and you can see how I reduced the bandwidth when goi= ng further=20 away. The minimum setting was 90 second dots, giving 0.042 Hz FFT reso= lution=20 when running at 4x normal samplerate (ie. 0.063 Hz noise BW) .<= /DIV>
 
The marginal "T" trace at 6 km was pr= obably no more=20 than 0 dB SNR. Thus the noise level (including spherics) would have be= en on the=20 order of 15 dBuV/m/sqrtHz.
 
Best 73,
Markus, DF6NM
 
_____________________________________= __
Von:=20 "Markus Vester" <markusve= ster@aol.com>
An: <rsgb_lf_group@blacksheep.org>
Betreff:=20 LF: Re: 9kHz noise level
Datum: Samstag, 27. Februar 2010 23:11
 
Dear Jim, LF,
 
yes I'm aware of the fact that the sh= ielding from=20 trees etc is more significant at lower frequency. Their ohmic conducta= nce=20 becomes a better shunt in comparison with decreasing capacitive admitt= ance,=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 deep= ly frozen,=20 but the effect on 9 kHz may have been more severe. A couple of years= ago our=20 neighbours had these trees chopped down, good for LF but otherwise=20 sad.
 
In April 2003, I attempted to transmi= tt an 8.97 kHz=20 carrier, radiating about 1 microwatt from my normal LF antenna (220 pF= at ~ 9m=20 eff. height). I drove around and stopped in different places, putting= up a 6m=20 fishing pole with a wire, connected to a resonant circuit and the lapt= op=20 soundcard. Each time I took a short Spectrogram full-band screenshot,= along with=20 a narrowband capture from a special Argo version, patched for 22 kHz= samplerate.=20 An assembly of the screenshots is at  http://freenet-homepage.de/df6nm/8970= _ALL.gif.=20 Maximum detection range was 6 km, just marginally outside the reactive= =20 nearfield. No noiseblanking was attempted at the time.
 
If you look at the Spectrogram strips= , you can see=20 that the first (1.6 km) and third (6.0 km) images have a much lower ab= solute=20 receive level. At first I thought something was wrong with the receive= antenna,=20 until I realized that this was purely due to these sites being in a fo= rested=20 area.
 
I have now rigged up SpecLab again fo= r VLF=20 reception. The Russian Alpha beacons seem to be usefiul calibration ma= rkers, the=20 nearest one is currently about 20 dB SNR here in a 42 Hz FFT. Does any= body in=20 the group have information about their EMRP, or has someone attempted= to measure=20 their fieldstrength in Europe?
 
Best 73,
Markus (DF6NM)
 
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