Return-Path: Received: from mtain-da09.r1000.mx.aol.com (mtain-da09.r1000.mx.aol.com [172.29.64.81]) by air-ma03.mail.aol.com (v127_r1.1) with ESMTP id MAILINMA031-b4f74b94d57f18b; Mon, 08 Mar 2010 05:46:23 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-da09.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3BFEE3800008A; Mon, 8 Mar 2010 05:46:21 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NoaS6-0008Qf-Jb for rs_out_1@blacksheep.org; Mon, 08 Mar 2010 10:44:46 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NoaS5-0008QW-QX for rsgb_lf_group@blacksheep.org; Mon, 08 Mar 2010 10:44:45 +0000 Received: from imr-da06.mx.aol.com ([205.188.169.203]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NoaS3-0001Hu-Tc for rsgb_lf_group@blacksheep.org; Mon, 08 Mar 2010 10:44:45 +0000 Received: from imo-ma03.mx.aol.com (imo-ma03.mx.aol.com [64.12.78.138]) by imr-da06.mx.aol.com (8.14.1/8.14.1) with ESMTP id o28AiP2Z024430 for ; Mon, 8 Mar 2010 05:44:25 -0500 Received: from MarkusVester@aol.com by imo-ma03.mx.aol.com (mail_out_v42.9.) id l.c5d.6b7b0105 (43956) for ; Mon, 8 Mar 2010 05:44:23 -0500 (EST) Received: from smtprly-de03.mx.aol.com (smtprly-de03.mx.aol.com [205.188.249.170]) by cia-dd01.mx.aol.com (v127_r1.2) with ESMTP id MAILCIADD015-b2524b94d4ff300; Mon, 08 Mar 2010 05:44:21 -0500 Received: from webmail-d097 (webmail-d097.sim.aol.com [205.188.255.8]) by smtprly-de03.mx.aol.com (v127.7) with ESMTP id MAILSMTPRLYDE036-b2524b94d4ff300; Mon, 08 Mar 2010 05:44:15 -0500 References: <2CDE578A1E1B49AF96D61BB5D91FA03D@White> <20100308082209.1C973F3862@smtps02.kuleuven.be> To: rsgb_lf_group@blacksheep.org Date: Mon, 08 Mar 2010 05:44:14 -0500 In-Reply-To: <20100308082209.1C973F3862@smtps02.kuleuven.be> X-MB-Message-Source: WebUI MIME-Version: 1.0 From: Markus Vester X-MB-Message-Type: User X-Mailer: AOL Webmail 30746-STANDARD Received: from 194.138.39.62 by webmail-d097.sysops.aol.com (205.188.255.8) with HTTP (WebMailUI); Mon, 08 Mar 2010 05:44:14 -0500 Message-Id: <8CC8CC36E425927-1F28-913E@webmail-d097.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: MarkusVester@aol.com X-Spam-Score: 1.2 (+) X-Spam-Report: autolearn=disabled,FORGED_AOL_TAGS=0.281,HTML_10_20=0.945,HTML_MESSAGE=0.001,UNPARSEABLE_RELAY=0.001 Subject: Re: LF: 12 km on Dream(ers) Band - TX loss calculation Content-Type: multipart/alternative; boundary="--------MB_8CC8CC36E5302C7_1F28_121DB_webmail-d097.sysops.aol.com" 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=FORGED_AOL_TAGS, HTML_FONTCOLOR_UNKNOWN,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: 3039ac1d40514b94d57d0cd5 X-AOL-IP: 193.82.116.20 ----------MB_8CC8CC36E5302C7_1F28_121DB_webmail-d097.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Dear Rik, LF, yes these numbers are pretty much where I arrived in my calculations. Ther= e is some loss in the transformer, about 1024* 0.25 ohm from the primary= and 60 ohm in the secondary, adding up to 315 ohm series loss. Thus anten= na resistance at 9 kHz would be more like 700 ohm. The same antenna has a= much lower resistance on 137 kHz, around 35 ohms normally, and down to 28= ohms in cold and dry weather. This includes the LF coil resistance (RF li= tz wire, Q ~ 700, Rcoil ~ 7 ohm). The large difference indicates that capa= citively coupled losses from high-resistance objects (trees, roof etc.) ar= e probably dominating at 9 kHz.=20 BTW I just noticed an error in the the 9 kHz coil description, it actually= has 10 sections, 500 turns each (back to kindergarten then to learn count= ing to ten ;-). Skin effect is probably still neglegible with the thin 0.2= mm wire, but there may be some eddy current loss (proximity effect) in th= e overlapping layers. Best 73, Markus -----Urspr=C3=BCngliche Mitteilung-----=20 Von: Rik Strobbe An: rsgb_lf_group@blacksheep.org Verschickt: Mo., 8. Mrz. 2010, 9:22 Thema: Re: LF: 12 km on Dream(ers) Band Hello Marcus, first of all congrats with your achievement. Based on the numbers you gave I tried to figure out the loss resistance at= 9kHz: - 35W and 0.135A would give 1920 Ohm.=20 - with a 32/1 transformer the TX (audio amp) would be loaded with 1.8 Ohm Assuming that the loss at 9kHz is slightly more than the DC loss (let's sa= y 900 Ohm) the "ground loss" (including greenery and buildings) would be= about 1 kOhm. Can you confirm this figures ? 73, Rik ON7YD At 21:16 6/03/2010, you wrote: Dear LF, =20 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/vl= f/vlf_12km.jpg =20 My transmit antenna is relatively small, about 220 pF and 9 m effective he= ight at 137 kHz. Assuming a 20% reduction due to shielding, radiation resi= stance 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 enamele= d wire, total DC resistance is 830 ohms. Fine tuning is achieved by shifti= ng 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). =20 I used the same 6 m portable receive antenna with series inductor as befor= e. I tried connecting directly to the microphone input of the netbook comp= uter, 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 alm= ost the same sensitivity, but resonance peaking was less critical with the= transistor. Postprocessing was now done using SpecLab, with software nois= e 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. =20 The lowest of the Alpha navigation frequencies was included in the decimat= ed 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 =3D 11904.762 Hz) is one of the weaker line= s here. But this depends on the relative phases of the two strongest stati= ons, 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: < rsgb_lf_group@blacksheep.org> 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 ca= n see how I reduced the bandwidth when going further away. The minimum set= ting was 90 second dots, giving 0.042 Hz FFT resolution when 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 th= e noise level (including spherics) would have been on the order of 15 dBuV= /m/sqrtHz. =20 Best 73, Markus, DF6NM =20 _______________________________________ Von: "Markus Vester" An: < rsgb_lf_group@blacksheep.org> 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 signif= icant 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 hi= gh 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 neig= hbours had these trees chopped down, good for LF but otherwise sad. =20 In April 2003, I attempted to transmitt an 8.97 kHz carrier, radiating abo= ut 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 pol= e 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 sample= rate. An assembly of the screenshots is at http://freenet-homepage.de/df6= nm/8970_ALL.gif. Maximum detection range was 6 km, just marginally outside= the reactive nearfield. No noiseblanking 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 level. At fi= rst I thought something was wrong with the receive antenna, until I realiz= ed 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 Alpha be= acons 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 infor= mation about their EMRP, or has someone attempted to measure their fieldst= rength in Europe? =20 Best 73, Markus (DF6NM) =20 ----------MB_8CC8CC36E5302C7_1F28_121DB_webmail-d097.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Dear Rik, LF,
 
yes these numbers are pretty much where I arrived in my cal= culations. There is some loss in the transformer, about  1024* 0.25= ohm from the primary and 60 ohm in the secondary, adding up to 315 ohm se= ries loss. Thus antenna resistance at 9 kHz would be more like 700 oh= m. The same antenna has a much lower resistance on 137 kHz, around 35 ohms= normally, and down to 28 ohms in cold and dry weather. This includes=  the LF coil resistance (RF litz wire, Q ~ 700, Rcoil ~ 7 ohm).= The large difference indicates that capacitively coupled losses from= high-resistance objects (trees, roof etc.) are probably dominating= at 9 kHz. 
 
BTW I just noticed an error in the the 9 kHz coil description, it act= ually has 10 sections, 500 turns each (back to kindergarten then to= learn counting to ten ;-). Skin effect is probably still neglegible with= the thin 0.2 mm wire, but there may be some eddy current loss (proximity= effect) in the overlapping layers.

Best 73,
Markus


-----Urspr=C3=BCngliche Mitteilung-----
Von: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
An: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>
Verschickt: Mo., 8. Mrz. 2010, 9:22
Thema: Re: LF: 12 km on Dream(ers) Band

Hello Marcus,<= br>
first of all congrats with your achievement.
Based on the numbers you gave I tried to figure out the loss resistance at= 9kHz:
- 35W and 0.135A would give 1920 Ohm.
- with a 32/1 transformer the TX (audio amp) would be loaded with 1.8 Ohm<= br> Assuming that the loss at 9kHz is slightly more than the DC loss (let's sa= y 900 Ohm) the "ground loss" (including greenery and buildings) would be= about 1 kOhm.
Can you confirm this figures ?

73, Rik  ON7YD

At 21:16 6/03/2010, you 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 occasio= ns, the carrier could be detected at a distance of 12.1 km: http://www.mydar= c.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 shieldin= g, radiation resistance would be around 74 microohms at 9 kHz. The 1.4 hen= ry loading coil is about 30 cm long by 12 cm diameter, and is split into= seven slightly conical sections, partly inserted into one another ( htt= p://www.mydarc.de/df6nm/vlf/9kHz_aircoil.jpg). Each section has 700 tu= rns 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 th= us approximately 1.3 uW (EMRP).
 
I used the same 6 m portable receive antenna with series in= ductor 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 tur= ned out to have almost the same sensitivity, but resonance peaking was les= s 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 expecte= d 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 rep= eating dashes, the beacon spectrum is split into several lines 1/3.6 Hz ap= art. The true center frequency (16*15625/21 =3D 11904.762 Hz) is one of th= e weaker lines here. But this depends on the relative phases of the two st= rongest 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 hop= e ;-) it won't last long...
 
Best wishes,
Markus (DF6NM)
 
_______________________________________
Von: "Markus Vester" <markusves= ter@aol.com>
An: < rsgb_lf_group@bla= cksheep.org>
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 corr= ect, 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) .
 
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" <markusves= ter@aol.com>
An: < rsgb_lf_group@bla= cksheep.org>
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, somew= hat similar to a C-R highpass equivalent circuit. There used to be two bea= utiful 15 m high fir trees in the vicinity of our house. At 137 kHz, I mea= sured a ~ 15% increase in effective height when the trees were deeply froz= en, 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 otherwis= e 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 ef= f. 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 lapt= op 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://free= net-homepage.de/df6nm/8970_ALL.gif. Maximum detection range was 6 km,= just marginally outside the reactive nearfield. No noiseblanking was atte= mpted 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 recei= ve 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 fores= ted 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 meas= ure their fieldstrength in Europe?
 
Best 73,
Markus (DF6NM)
 
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