Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 4B7B038000116; Sat, 30 Jul 2011 14:04:10 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QnDsB-0005VG-5m for rs_out_1@blacksheep.org; Sat, 30 Jul 2011 19:02:51 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QnDs9-0005V7-N8 for rsgb_lf_group@blacksheep.org; Sat, 30 Jul 2011 19:02:49 +0100 Received: from bay0-omc1-s4.bay0.hotmail.com ([65.54.190.15]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QnDs7-0003qN-22 for rsgb_lf_group@blacksheep.org; Sat, 30 Jul 2011 19:02:49 +0100 Received: from BAY154-W3 ([65.54.190.61]) by bay0-omc1-s4.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Sat, 30 Jul 2011 11:02:39 -0700 Message-ID: X-Originating-IP: [81.200.63.88] From: Lubos OK2BVG To: _RSGB_LF Date: Sat, 30 Jul 2011 20:02:39 +0200 Importance: Normal In-Reply-To: <4E33EAB8.2020209@iup.uni-heidelberg.de> References: <44B95F8B497148E4ADFB54AC46CEAA38@White>,<4E33EAB8.2020209@iup.uni-heidelberg.de> MIME-Version: 1.0 X-OriginalArrivalTime: 30 Jul 2011 18:02:39.0180 (UTC) FILETIME=[DEA480C0:01CC4EE2] X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Content-Type: multipart/alternative; boundary="_8134c459-ef7d-457d-bab2-bc90e269b3b1_" Subject: RE: VLF: DF6NM kite attempt 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=FORGED_HOTMAIL_RCVD,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-SCORE: 1:2:494949120:93952408 X-AOL-SCOLL-URL_COUNT: 1 x-aol-sid: 3039ac1d40854e34479a79fe X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --_8134c459-ef7d-457d-bab2-bc90e269b3b1_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Markus=2C Stefan and other VLF fans!I am very glad to see strong sign= al on my VLF grabber. I was out of my home=2C so I noticed this signal jus= t now. GREAT! Well done=2C Markus! 73! Lubos=2C OK2BVG Date: Sat=2C 30 Jul 2011 13:27:52 +0200 From: schaefer@iup.uni-heidelberg.de To: rsgb_lf_group@blacksheep.org Subject: Re: VLF: DF6NM kite attempt =20 VLF=2C Markus produces a strong signal=2C he is well visible in my DFCW-60 window at 8970.002 Hz in 174 km distance. He is 13 dB S/N at OK2BVG in 600!!! A trace seems to come up at G3ZJO in the 6000 window. A small peak seems to come up at TF3HZ... http://simnet.is/halldorgudmunds/TF3HZ_VLFgrabber/index.html http://www.ok2bvg.cz/vlfgrabber/ http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html http://g3zjo.bplaced.net/index.htm Any other receiving stations? I think this is his best signal radiated so far :-) The DX season is coming back! :-) 73=2C GL=2C=20 Stefan/DK7FC Am 30.07.2011 09:52=2C schrieb Markus Vester: =20 =20 =20 Dear LF=2C =20 today around noon=2C I will attempt another kite transmission from the same site. If all works well=2C I will send a 1 mW carrier on 8970.002 from around 11 to 14 UT. =20 Best regards=2C Markus (DF6NM) =20 =20 =20 =20 From: Markus Vester=20 =20 =20 =20 =20 Sent: Tuesday=2C June 21=2C 2011 12:00 AM To: rsgb_lf_group@blacksheep.org =20 Subject: VLF: DF6NM kite activity June 19 =20 =20 =20 =20 Dear Dreamers=2C =20 thanks very much to everyone who commented on my signal yesterday night=2C and all who are running their VLF grabbers. =20 Transmission: =20 My signal was on air on 8970.002 Hz from 18:52 to 22:01=2C with a long break from 19:26 to 19:52 due to a prolonged rain period=2C and many shorter interruptions caused by precipitation=2C low wind=2C a coil falling over=2C or a breaking antenna connection. =20 I'm aware that an advanced notice would have been valuable for potential receiving stations. But I find it difficult to plan ahead this type of activity. Yesterday even while setting things up on the site=2C I was not at all sure whether I would be able to actually get on air for any significant time.=20 =20 Site: =20 The location (49.3874 N 11.1692 E=2C "JN59OJ02HX" for those who prefer cryptic notations =3B-) was the same as in the experiment on Nov 13 last year (see email copy at bottom). While Google Maps still shows large patches of unused land around the former US airfield=2C "my" field is now one of very few undeveloped plots in the middle of an industrial area=2C inhabited mostly by large logistics companies. Though I had originally not intended to work into darkness=2C I found there was still plenty of light from the surrounding truck parking and unloading areas. =20 Kite antenna and ground: =20 This time I used a 4 sqm lifter kite (HQ Power Sled L3.0=2C similar to Stefan's smaller kite). It is held by a 150 m line. This may be stretching the limit a bit=2C but due to the slope and sag of the line I am sure that the peak altitude always stayed below 100 m. =20 =20 The previously used 0.4 mm magnet wire had a voltage limit of about 12 kV due to corona appearing along the whole length. It has now been replaced by insulated wire (0.25 sqmm=2C outer diameter 1.3 mm). The total length is 180 m=2C with the last 30 m dangling down from the kite=2C intended to act as a sort of extra top load. Effective height would be around 50 m=2C giving 3.5 milliohm radiation resistance=2C or 1.3 mW EMRP at 0.6 A. =20 At the western end of the unused site=2C there is a long mesh wire fence running north-south=2C held by solid metal posts which served very well both for anchoring and grounding. Total resistance of the antenna circuit was around 280 ohms (including 140 ohms for the coil). This is about half of that when I used the same kite antenna in Bamberg with only a few short ground pegs. =20 =20 The coil was placed below the kite line at about 3 m from the anchor point=2C hoping to keep the wire well above ground. However this turned out to be problematic due to the horizontal and vertical movement of the connection point. When the kite was low and due west=2C the wire was too long and touched the wet grass=2C exhibiting pretty little fireworks. When it went up or drifted aside=2C the wire became too short=2C and either plugged itself off=2C or tipped over the whole coil. You guess how much I like having to reconnect the ungrounded wire=2C with dark clouds overhead and a slight drizzle going down... I twice found myself holding down the kite line with my foot=2C then slowly stepping forward until the open end at least touched the earth. Next time I will definitely place the coil much closer to the anchor=2C and try to hold the connection up by means of some elastic plastic tube. =20 Coil: =20 From the previous experiment I knew that the wire capacitance was very close to 900 pF. During the afternoon=2C I experimented with different coil configurations=2C and found that I could either use four buckets (184 ohms) with a large 10 cm pitch (ie. 9 Lego blocks)=2C giving about 8 mm radial clearance between one coil layer and the inner radius of the next bucket. The other option was three buckets (138 ohms)=2C stuffed into one another 3 cm pitch and 2 mm clearance (see picture http://df6nm.bplaced.net/VLF/pictu= res/two_coils_350mH.jpg). =20 Mainly for mechanical reasons=2C I opted for the more compact three-bucket solution=2C but this turned out to be the wrong choice. With power applied=2C I heard corona sizzles around the coil at about 0.55 A (11 kV). In darkness I could see violet seams near the bottom end of the upper two windings. This means that the maximum usable layer-to-layer voltage for this design is about 3.7 kV. Next time I will definitely go for the longer version=2C which also has more surface exposed to the wind for heat removal. =20 BTW all seven buckets connected to 900 pF resonate at about 4.6 kHz - Stefan=2C how about a 65 km band =3B-) =20 Amplifier and power supply: =20 Like before=2C I used one channel of a class-B car-audio amp (Nitro 3000)=2C feeding a 12 : 80 turns ferrite transformer originally wound by DJ2LF. It delivered 0.6 A antenna current (~ 100 W) from 12V x 13 A DC input. It was possible to turn the volume up to 0.7A=2C but I did not dare to run that level of corona permanently. The amp was fed by a standalone 35 Ah lead-acid battery=2C which was repeatedly recharged via jumper wires from the car engine during the latter half of the experiment. =20 Signal generation: =20 SpecLab's samplerate was locked to DHO=2C which is very slightly (3 ppb) above its nominal frequency 23.4 kHz. To keep the average phase steady=2C I took care to never interrupt the software generator whenever I had to take the carrier off air. Anyway the time series recorded by Paul Nicholson shows two major phase jumps around 19:40 (while the TX was off) and 21:20=2C perhaps due to soundcard buffering issues. One problem I did not see immediately was that the DHO ferrite antenna was too close to one of the jumper wires=2C temporarily picking up interference when the car alternator was running - once found=2C this one was easily fixed. =20 Results: =20 Though the traces at TF3HZ (2547 km) and YO/4X1RF (1253 km) are close to the noise=2C they are at the right time and frequency=2C and I do not think that they are random pixels. Halld=F3r's trace even seems to show the outage period after the first bright dot.=20 =20 On my own grabber=2C I attempted to compare signal levels from DK7FC (-71 dB=2C 180 km) and myself (-43 dB=2C 4.5 km). Correcting this difference (28 dB) by the EMRP ratio (26 mW / 1.2 mW =3D 13 dB)=2C distance ratio (1/r =3D 32 dB) plus an additional nearfield correction (1/r=B3 instead of 1/r from 4.5 to 5.3 km =3D 3 dB)=2C we find that Stefan was 28+13-35 dB =3D 6 dB weaker than we would expect by pure groundwave. This corresponds very well to the earlier experience that there is a midday skywave cancellation effect for about 200 km.=20 =20 Best wishes=2C Markus (DF6NM) =20 From: Stefan Sch=E4fer=20 Sent: Monday=2C June 20=2C 2011 10:48 AM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: VLF: DF6NM on 8970 Hz!! Fwd: Fwd: VLF: More food for grabbers =20 =20 Hello Markus=2C=20 =20 This was your strongest signal received here so far. Tell us about your rig! Where did the TX power come from? A battery? Must have been a big battery or you must have had very low losses. =20 Transmitting during the night could be an interesting point. I could try to use the 100m kite antenna on 8970 Hz as well. Then=2C no special permit would be needed but my signal would be 10 dB lower. Anyway this could be interesting. Or i could try night transmissions on the fixed antenna.... =20 Happy to see more activity here again! :) =20 73=2C Stefan/DK7FC ________________________________________ =20 From: Markus Vester=20 Sent: Sunday=2C November 14=2C 2010 12:04 AM To: rsgb_lf_group@blacksheep.org =20 Cc: Paul=20 Subject: Re: VLF: TX on 6.47 and 8.97 =20 =20 Dear LF=2C Paul=2C =20 here's a short summary of today's VLF kite transmission. I'm sorry for the late notice=2C but the experiment had not been planned ahead=2C and I wasn't sure if I could get on at all. Also=2C the kite I am using (a 0.8 m^2 delta toy bought for 4.99 Euro) is a bit small for this sort of activity=2C and really requires a good and steady wind. =20 =20 The QTH was actually at 49.3874 N 11.1692 E=2C a few 100 meters from the former location reported earlier. The GPS-controlled carriers were on air=20 11:15 - 12:15 6470.000 Hz ~ 50 uW=2C and=20 12:30 - 13:10 8970.002 Hz ~ 200 uW (EMRP). =20 Getting on 6470 was easier than expected. I simply used the same "seven-bucket" coil=2C which resonates my 240 pF home antenna to 8.97 kHz. Connected to the kite wire=2C the resonance was close enough to 6.5 kHz to be tuned by the ferrite plate variometer. Then the drive for the audio amp was increased until the onset of corona sizzling at 0.25 A. At that point=2C the amp drew 10 A DC from the car battery and probably delivered around 50 W. After connecting mobile internet and staring at Stefan's grabber=2C I was positively surprised to find a faint trace there! =20 For the frequency change=2C I removed the two bottom coil buckets=2C which brought the resonance to ~ 8.5 kHz. Then I had to carefully pull the remaining 5 buckets apart=2C inserting bits of plastic foam material as spacers. Going through a few iterations took about 10 minutes=2C and I got to "full power" (380 mA=2C 100W) at 12:30. Unfortunately=2C the wind had started to calm by then=2C and there were several dips during this transmission. Finally at 13:10=2C the kite landed gently in the grass=2C and I decided to close down and pack up early. =20 Traces from both transmissions were visible on DK7FC's 4.5 mHz "600" windows=2C and the second one also produced a nice dash on the 0.45 mHz window. It is likely that these signals would be useful for a kite-to-kite QSO on either frequency=2C using 10 minute dashes. =20 The screenshot from F1AFJ has an interesting dash before 13:00. The indicated frequency seems a bit high (8970.020 instead of 8970.002)=2C which could perhaps be due to a small samplerate calibration error. I am also not sure about the time scale - judging by the width of the noise blobs=2C the setting could have been 11 mHz and 10 seconds per pixel. It would be nice if Jean-Pierre could confirm the frequency calibration and scroll settings. =20 I also carefully inspected the OE3GHB grabber=2C which runs at 1.4 mHz resolution and seems to be very sensitive. It showed an unusually dark period of very low noise between 8 and 11 UT today. But no luck for my transmission there yet. =20 Well=2C in addition to the technical aspects=2C being outdoors in the warm wind was again a rewarding and enjoyable experience.=20 =20 Best 73=2C and thanks again for the interest.=20 =20 Markus (DF6NM) =20 ... =20 = --_8134c459-ef7d-457d-bab2-bc90e269b3b1_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Markus=2C Stefan and other VLF fans!
I am very glad to see strong= signal on my VLF grabber.  =3BI was out of my home=2C so I noticed thi= s signal just now. =3B
GREAT! Well done=2C Markus!
=
73!

Lubos=2C OK2BVG


Date: Sat=2C 30 Jul 2011 13:27:52 +0200=
From: schaefer@iup.uni-heidelberg.de
To: rsgb_lf_group@blacksheep.or= g
Subject: Re: VLF: DF6NM kite attempt

=20 VLF=2C

Markus produces a strong signal=2C he is well visible in my DFCW-60 window at 8970.002 Hz in 174 km distance. He is 13 dB S/N at OK2BVG in 600!!! A trace seems to come up at G3ZJO in the 6000 window. A small peak seems to come up at TF3HZ...

http://simnet.is/halldor= gudmunds/TF3HZ_VLFgrabber/index.html
http://www.ok2bvg.cz/vlfgrabber/
http://www.iup.u= ni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html
http://g3zjo.bplaced.net/index.htm

Any other receiving stations?

I think this is his best signal radiated so far :-)

The DX season is coming back! :-)

73=2C GL=2C

Stefan/DK7FC

Am 30.07.2011 09:52=2C schrieb Markus Vester:
=20 =20
Dear LF=2C
 =3B
today around noon=2C I will attempt another kite =3Btransmission from the same site. If all works well=2C I will =3Bsend =3Ba =3B1 mW carrier on 8970.002 =3Bfrom aroun= d 11 to 14 UT.
 =3B
Best regards=2C
Markus (DF6NM)
Sent: Tuesday=2C June 21=2C 2011 12:00 AM
Subject: VLF: DF6NM kite activity June 19

Dear Dreamers=2C
 =3B
thanks very much to everyone who commented =3Bon my signal yesterday night=2C&= nbsp=3Band all who =3Bare running their VLF grabbers.
 =3B
Transmission:
 =3B
My signal was on air on 8970.002 Hz from 18:52 to 22:01=2C with a long break from 19:26 to 19:52 due to a prolonged rain period=2C and =3Bmany short= er interruptions caused by precipitation=2C low wind=2C a coil falling over=2C or a breaking antenna connection.
 =3B
I'm aware that an advanced notice would have been valuable =3Bfor potential =3Breceiving stations. But =3BI find it difficult to = =3Bplan ahead =3Bthis type of =3Bactivity. Yesterday even while setting thi= ngs up on the site=2C I was not at all sure =3Bwhether I would be able to actuall= y get on air for any significant time.
 =3B
Site:
 =3B
The =3Blocation (49.3874 N 11.16= 92 E=2C "JN59OJ02HX" for those who =3Bprefer cryptic notations =3B-) =3Bwas= the same =3Bas =3Bin the experiment =3Bon Nov 13 last year (see ema= il copy =3Bat bottom). =3BWhile Google Maps still shows =3Blarge patches of unuse= d land around the =3Bformer =3BUS =3Bairfield=2C =3B"my" field&nbs= p=3Bis =3Bnow =3Bone of very few =3Bundeveloped plots in the middle of an industrial area=2C inhabit= ed mostly by large logistics companies. Though=  =3BI had originally =3Bnot intended to work into darkness=2C =3BI found = there was still =3Bplenty of light from the surrounding truck parking and unloadi= ng areas.
 =3B
Kite antenna and ground:
 =3B
This time =3BI used a =3B4 s= qm lifter kite (HQ Power Sled L3.0=2C similar to =3BStefan's smaller kite). It is held= by a 150 m line. This may be stretching the limit a bit=2C but due to the slope and sag of the line I am sure that the =3Bpeak altitude =3Bal= ways stayed below =3B100 m.
 =3B
The previously used =3B0.4 mm magnet wire =3Bhad a voltage limit = =3Bof about 12 kV due to corona appearing along the whole length. It has now been replaced =3Bby insulated wire (0.25 sqmm=2C outer diameter 1.3 mm). The total length is 180 m=2C =3Bwith the last 30 m dangling down from the k= ite=2C intended to act as a sort of extra top load. Effective height would be around 50 m=2C giving 3.5 milliohm radiation resistance=2C or 1.3 mW EMRP at 0.6 A.
 =3B
At the western end of the unused site=2C there is a long mesh wire fence running =3Bnorth-south=2C = =3Bheld by solid metal posts which =3Bserved =3Bvery well both for anchoring a= nd grounding. Total resistance of the antenna circuit was around 280 ohms (including 140 ohms for the coil). This is about half of =3Bthat = =3Bwhen I used the same kite antenna =3Bin Bamberg with only a few short ground p= egs.
 =3B
The coil was placed below the kite line at about 3 m =3Bfrom the anchor point=2C hoping to keep the =3Bwire well above ground. However t= his turned out to be problematic =3Bdue to the horizontal and vertical movement of the connection point. When the kite was low and due west=2C the =3Bwire =3Bwas too long and touched the wet grass=2C exhibiting=  =3Bpretty little fireworks. When it went up or drifted aside=2C the =3Bwire becam= e too short=2C and either plugged itself off=2C or tipped over the whole coil. You guess how much =3BI like having to reconnect the ungrounded wire=2C= with dark clouds overhead and a slight drizzle going down... =3BI twice foun= d myself =3Bholding down the =3Bkite line with my foot=2C then slowly= stepping forward until the open end at least touched the earth. =3BNext time I will =3Bdefinitely place the coil =3Bmuch closer to the anchor=2C a= nd try to hold the =3Bconnection up =3Bby means =3Bof some elastic plasti= c tube.
 =3B
Coil:
 =3B
From the previous experiment I knew that the wire capacitance was very close to 900 pF. During the afternoon=2C I experimented with =3Bdifferent =3Bcoil configuration= s=2C and found that I could either use =3Bfour buckets (184 ohms) with a =3Blarge&= nbsp=3B10 cm =3Bpitch (ie. =3B9 Lego blocks)=2C giving =3Babout 8 mm radi= al clearance between one coil layer and the inner radius =3Bof the next bucket. = =3BThe other option =3Bwas =3Bthree buckets (138 ohms)=2C stuffed into one=  =3Banother =3B3 cm pitch =3Band 2 mm clearance (see picture http://df6nm.bplace= d.net/VLF/pictures/two_coils_350mH.jpg).
 =3B
Mainly for mechanical reasons=2C I opted for the more compact three-bucket solution=2C =3Bbut this =3B= turned out to be the wrong choice. =3BWith power applied=2C I heard corona =3Bsizzles =3Baround the coil at about 0.55 A (11 kV). = =3BIn darkness I could see =3Bviolet seams near the bottom end of the upper two windings= . This means that the maximum usable layer-to-layer voltage for this design is about =3B3.7 kV. Next time I will definitely =3Bgo for th= e longer version=2C which also has more surface exposed to the wind for heat removal.
 =3B
BTW =3Ball =3Bseven buckets = connected to 900 pF =3Bresonate =3Bat about 4.6 kHz - Stefan=2C how about a 65 k= m band =3B-)
 =3B
Amplifier and power supply:
 =3B
Like before=2C I =3Bused one cha= nnel of =3Ba =3Bclass-B car-audio amp (Nitro 3000)=2C =3Bfeeding a 1= 2 : 80 turns ferrite transformer originally wound by DJ2LF. It delivered =3B0.6 A antenna current (~ 100 W) =3Bfrom 12V x 13 A =3BDC input. =3BIt= was possible to turn the volume up to 0.7A=2C but I did not =3Bdare =3Bto =3Bru= n =3Bthat =3Blevel of corona permanently. =3BThe amp was fed by a standalone 35 Ah lead-acid battery=2C which =3Bwas =3Brepeatedly recharged via =3Bjumper w= ires from the car engine during the latter half of the experiment.
 =3B
Signal generation:
 =3B
SpecLab's samplerate =3Bwas lock= ed to DHO=2C which =3Bis very slightly (3 ppb) above =3Bits nominal frequ= ency 23.4 kHz. =3BTo keep the average phase steady=2C I took care to never interr= upt the software generator whenever I had to take the =3Bcarrier off air. =3BAnyway the =3Btime series r= ecorded by Paul Nicholson =3Bshows two major phase jumps =3Baround 19:40 (whil= e the TX was off) and 21:20=2C perhaps due to soundcard buffering issues. =3BOne problem I did not see immediately was that the DHO ferrite antenna was too close to one of the jumper wires=2C =3Btemporarily picking up interference when =3Bthe car alternator was running - once found=2C thi= s one was easily fixed.
 =3B
Results:
 =3B
Though the traces at TF3HZ (2547 km) and YO/4X1RF (1253 km) are close to the noise=2C =3Bthey are at the rig= ht time and frequency=2C and I =3Bdo not think =3Bthat they are = =3Brandom pixels. Halld=F3r's trace even seems to show the outage period after the first bright dot. =3B
 =3B
On my own grabber=2C I attempted to =3Bcompare =3Bsignal levels from =3BDK7FC (-71 dB=2C 180 km)= and myself (-43 dB=2C 4.5 km). =3BCorrecting this difference (28 dB) by =3Bthe EMRP= ratio (26 mW =3B/ 1.2 mW =3D 13 dB)=2C distance ratio (1/r =3D 32 dB) =3Bplus=  =3Ban additional =3Bnearfield correction (1/r=B3 instead of 1/r from 4.5 to 5= .3 km =3B=3D 3 dB)=2C we =3Bfind that Stefan was =3B28+13-35 dB =3D 6 dB weaker than we would expect by pure groundwave. This corresponds very well to the earlier experience that there is a midday skywave cancellation effect for about 200 km. =3B
 =3B
Best wishes=2C
Markus (DF6NM)
 =3B
From: <= a title=3D"mailto:schaefer@iup.uni-heidelberg.de STRG + Klicken=2C um Verkn=FCpfung zu folgen" href=3D"mailto:schaefer@iup.u= ni-heidelberg.de">Stefan Sch=E4f= er
Sent: Monday=2C June 20= =2C 2011 10:48 AM
Subject: Re: VLF: DF6NM on 8970 Hz!! Fwd: Fwd: VLF: More food for grabbers

Hello Markus=2C

This was your strongest signal received here so far. Tell us about your rig! Where did the TX power come from? A battery? Must have been a big battery or you must have had very low losses.

Transmitting during the night could be an interesting point. I could try to use the 100m kite antenna on 8970 Hz as well. Then=2C no special permit would be needed but my signal would be 10 dB lower. Anyway this could be interesting. Or i could try night transmissions on the fixed antenna....

Happy to see more activity here again! :)

73=2C Stefan/DK7FC
____________________________________= ____
 =3B
Sent: Sunday=2C Novembe= r 14=2C 2010 12:04 AM
Subject: Re: VLF: TX on 6.47 and 8.97

Dear =3BLF=2C Paul=2C
 =3B
here's a short summary of today's VLF kite transmission. I'm sorry for the late notice=2C but the =3Bexperiment had =3Bnot been planned =3Bahead=2C and I was= n't sure if I could get on at all. Also=2C the kite I am using =3B(a 0.8 m^2 =3Bdelta t= oy bought for =3B4.99 Euro) =3Bis a bit small for this sort of activity=2C an= d really requires a good and steady wind. =3B =3B
 =3B
The QTH was actually at 49.3874 N 11.1692 E=2C a few 100 meters from the former location reported earlier. The GPS-controlled carriers were on air
 =3B11:15 - 12:15 =3B 6470.0= 00 Hz ~ 50 uW=2C and
 =3B12:30 - 13:10 =3B 8970.0= 02 Hz ~ 200 uW (EMRP).
 =3B
Getting on 6470 was easier than expected. I simply used the same "seven-bucket" coil=2C which resonates my 240 pF home antenna to 8.97 kHz. Connected to the kite wire=2C the resonance was close enough to 6.5 kHz to be tuned by the ferrite plate variometer. =3BThen the =3Bdrive for the audio amp was increased&nb= sp=3Buntil the onset of corona sizzling at 0.25 A. =3BAt that point=2C =3Bthe amp = drew 10 A DC from the car battery and probably delivered around 50 W. After connecting mobile internet and staring at Stefan's grabber=2C I was positively surprised to =3Bfind a faint trace there!
 =3B
For the frequency change=2C I remove= d the =3Btwo bottom coil buckets=2C which brought the resonance to ~ 8.5 = kHz. Then I had to carefully pull the remaining 5 buckets apart=2C =3Binsert= ing bits of plastic foam =3Bmaterial =3Bas =3Bspacers. =3BGoing= through a =3Bfew iterations took about 10 minutes=2C and I got to "full power" =3B(380 m= A=2C 100W) at 12:30. Unfortunately=2C the wind had started to calm by then=2C and there were several dips during this transmission. Finally at 13:10=2C the kite landed gently in the =3Bgrass=2C and I decided to close down a= nd pack up early.
 =3B
Traces from both transmissions were visible on DK7FC's 4.5 mHz "600" windows=2C and =3Bthe second one also produced a =3Bnice dash on the 0.45 mHz window. It is likely that these signals would be useful for a kite-to-kite QSO on either frequency=2C using 10 minute dashes.
 =3B
The =3Bscreenshot from F1AFJ&nbs= p=3Bhas an interesting dash before 13:00. =3BThe indicated frequency seems a bit h= igh (8970.020 instead of 8970.002)=2C which could perhaps be due to a small samplerate calibration error. I am also not sure about the time scale =3B =3B- judging by the width of the noise blobs=2C the setti= ng could have been 11 mHz and =3B10 seconds per pixel. It would be nice if =3BJean-Pierre =3Bcould confirm the frequency calibration and sc= roll settings.
 =3B
I also carefully inspected the OE3GHB grabber=2C which =3Bruns at 1.4 mHz resolution and seems to be v= ery sensitive. It showed an unusually =3Bdark period of very low noise betw= een 8 and 11 UT today. But no luck =3Bfor my transmission there yet.=
 =3B
Well=2C in addition t= o the technical aspects=2C being outdoors in the warm wind was again a =3Brewarding and enjoyable experience.
 =3B
Best 73=2C and thanks= again for the interest.
 =3B
Markus (DF6NM)=
 =3B
...
 =3B
= --_8134c459-ef7d-457d-bab2-bc90e269b3b1_--