Return-Path: Received: from mtain-mc08.r1000.mx.aol.com (mtain-mc08.r1000.mx.aol.com [172.29.96.80]) by air-ma04.mail.aol.com (v127_r1.1) with ESMTP id MAILINMA044-b5234b92beb831; Sat, 06 Mar 2010 15:44:40 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mc08.r1000.mx.aol.com (Internet Inbound) with ESMTP id 47696380000F0; Sat, 6 Mar 2010 15:44:38 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1No0qc-0001VD-A2 for rs_out_1@blacksheep.org; Sat, 06 Mar 2010 20:43:42 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1No0qb-0001V4-J0 for rsgb_lf_group@blacksheep.org; Sat, 06 Mar 2010 20:43:41 +0000 Received: from mail-bw0-f211.google.com ([209.85.218.211]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1No0qY-0002XC-Iq for rsgb_lf_group@blacksheep.org; Sat, 06 Mar 2010 20:43:41 +0000 Received: by bwz3 with SMTP id 3so1277036bwz.29 for ; Sat, 06 Mar 2010 12:43:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=Sr1HWb4SJnuCw9tGj+OPYtNM2FSb2i15ZeGFeCzq15A=; b=ANfUv0hcYd8gtsRPH28Fsl0ufx/QJiv5NcMvLUm6CbQqhGgNlRIwIvpEY6XeE4BpLT 4MzLgOAgGDYrUxVd0w/UD8+s+lRK/VGlJenVaH7/V9lyD7ukdhsTasBHxLPsbL4y44yI t2UxhzmFArbcoMGwPoc1pl+Fx9S4sUbI0vTtY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=VFwItmVUtU9fEc0UezsAyQgYTTEpzPL4EvVMHaoB7WgYyK+2BBJKW9gwrF63GxhZhf oMxIgXlmLn9cblMDg7TBin5MOJQTV8WMM9Ve3LdLAvdXmKHAXbLEvsO/lWcVnHIwj+Hj /O9kGXsNLhezd4Ag1grNxbF5Odaf58xw3iddw= MIME-Version: 1.0 Received: by 10.204.151.91 with SMTP id b27mr2236932bkw.110.1267908212671; Sat, 06 Mar 2010 12:43:32 -0800 (PST) In-Reply-To: <2CDE578A1E1B49AF96D61BB5D91FA03D@White> References: <2CDE578A1E1B49AF96D61BB5D91FA03D@White> Date: Sat, 6 Mar 2010 20:43:32 +0000 Message-ID: <9afca2641003061243y38e8a82ci149847111466e1ab@mail.gmail.com> From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: 12 km on Dream(ers) Band Content-Type: multipart/alternative; boundary=00151761c7b49fc5ec048127e203 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-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m268.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d60504b92beb63668 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --00151761c7b49fc5ec048127e203 Content-Type: text/plain; charset=ISO-8859-1 Excellent Marcus - very well done. This is extremely encouraging to the rest of us. 73s Roger G3XBM On 6 March 2010 20:16, Markus Vester wrote: > 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 locations. The > experiment was very similar to the one in April 2003, but with a moderate > improvement in ERP and FFT bandwidth. Now on both occasions, 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 effective > height at 137 kHz. Assuming a 20% reduction due to shielding, radiation > 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 ( > http://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 transformer, I now > got up to 0.135 A and 11 kV rms at the antenna. Radiated power 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 netbook > computer, and also inserting a simple bipolar preamplifier, which was fed > from the 2.5 VDC present at the mic jack. Both versions turned 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 noise level on the order of 16 dBuV/m/sqrtHz. > However on the last receive site at 15.4 km, no trace of the signal could be > retrieved. > > The lowest of the Alpha navigation frequencies was included in the > decimated frequency range to check soundcard drift. Due to the repeating > dashes, the beacon spectrum is split into several lines 1/3.6 Hz apart. The > true center frequency (16*15625/21 = 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. However > 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 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 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. Thus 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 > significant 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 beautiful 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. height). I > drove around and stopped in different places, putting up a 6m fishing pole > with a wire, connected to a resonant circuit and the laptop soundcard. Each > time I took a short Spectrogram full-band screenshot, along with a > narrowband capture from a special Argo version, patched 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 noiseblanking 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 level. 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. > > I have now rigged up SpecLab again for VLF reception. The Russian Alpha > 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 group have > information about their EMRP, or has someone attempted to measure their > fieldstrength in Europe? > > Best 73, > Markus (DF6NM) > > -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/G3XBM G3XBM GQRP 1678 ISWL G11088 --00151761c7b49fc5ec048127e203 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Excellent Marcus - very well done.=A0 This is extremely encouraging to the= rest of us.

73s
Roger G3XBM



On 6 March 2010 20:16, Markus Vester <markusvester@aol.com> wrote= :
Dear LF,
=A0
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 200= 3, but=20 with a moderate improvement in ERP and FFT bandwidth. Now on both occasion= s, the=20 carrier could be detected at a distance of 12.1 km:=A0http://www.mydarc.de= /df6nm/vlf/vlf_12km.jpg
=A0
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 int= o=20 seven slightly conical sections, partly inserted into one another (http://www.mydarc.de/df6nm/vlf/9kHz_aircoil.jpg= ).=20 Each section has 700 turns of 0.2 mm enameled wire, total DC resistance is= 830=20 ohms. Fine tuning is achieved by shifting a thick block of ferrite into th= e last=20 section. Using a 35 W car-radio audio amplifier and a 1:32 ferrite transfo= rmer,=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).
=A0
I used the same 6 m portable receive= antenna with=20 series inductor as before. I tried connecting directly to the microphone= input=20 of the netbook computer, and also inserting a simple bipolar preamplifier,= 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 critical= with=20 the transistor. Postprocessing was now done using SpecLab, with software= 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. Ho= wever=20 on the last receive site at 15.4 km, no trace of the signal could be=20 retrieved.
=A0
The lowest of the Alpha navigation fr= equencies was=20 included in the decimated frequency range to check soundcard drift. Due 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 stro= ngest=20 stations, and will be different in other areas.
=A0
The reception could possibly be a new= amateur VLF=20 distance record. However with all the ongoing activity, I expect (and actu= ally=20 hope ;-) it won't last long...
=A0
Best wishes,
Markus (DF6NM)=
=A0
_____________________________________= __
Von:=20 "Markus Vester" <markusvester@aol.com>
An: <rsgb_lf_group@blacksheep.org= >
Betreff:=20 LF: Re: 9kHz noise level
Datum: Sonntag, 28. Februar 2010 14:06<= /div>
=A0
Dear Alexander, LF,
=A0
the frequency rulers of the modified= Argo are=20 actually correct, and you can see how I reduced the bandwidth when going= further=20 away. The minimum setting was 90 second dots, giving 0.042 Hz FFT resoluti= on=20 when running at 4x normal samplerate (ie. 0.063 Hz noise BW) .
=A0
The marginal "T" trace at= 6 km was probably no more=20 than 0 dB SNR. Thus the noise level (including spherics) would have been= on the=20 order of 15 dBuV/m/sqrtHz.
=A0
Best 73,
Markus, DF6NM
=A0
_____________________________________= __
Von:=20 "Markus Vester" <markusvester@aol.com>
An: <rsgb_lf_group@blacksheep.org= >
Betreff:=20 LF: Re: 9kHz noise level
Datum: Samstag, 27. Februar 2010 23:11<= /div>
=A0
Dear Jim, LF,
=A0
yes I'm aware of the fact that th= e shielding from=20 trees etc is more significant at lower frequency. Their ohmic conductance= =20 becomes a better shunt in comparison with decreasing capacitive admittance= ,=20 somewhat similar to a C-R highpass equivalent circuit. There used to be tw= o=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 deeply= 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.
=A0
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 laptop= =20 soundcard. Each time I took a short Spectrogram full-band screenshot, alon= g with=20 a narrowband capture from a special Argo version, patched for 22 kHz sampl= erate.=20 An assembly of the screenshots is at=A0 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.
=A0
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 absolu= te=20 receive level. At first I thought something was wrong with the receive ant= enna,=20 until I realized that this was purely due to these sites being in a forest= ed=20 area.
=A0
I have now rigged up SpecLab again fo= r VLF=20 reception. The Russian Alpha beacons seem to be usefiul calibration marker= s, the=20 nearest one is currently about 20 dB SNR here in a 42 Hz FFT. Does anybody= in=20 the group have information about their EMRP, or has someone attempted to= measure=20 their fieldstrength in Europe?
=A0
Best 73,
Markus (DF6NM)
=A0



--

http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/G3XBM
G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088
--00151761c7b49fc5ec048127e203--