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[129.206.22.206]) by mx.google.com with ESMTPSA id o12sm57822155wiw.5.2014.06.25.14.11.31 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 25 Jun 2014 14:11:31 -0700 (PDT) From: DK7FC <73dk7fc@googlemail.com> X-Google-Original-From: DK7FC <73dk7fc@gmail.com> Message-ID: <53AB3B02.2010102@gmail.com> Date: Wed, 25 Jun 2014 23:11:30 +0200 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <53A97738.2070501@gmail.com> <8D15DE5531A8822-27BC-8EBC@webmail-m293.sysops.aol.com> In-Reply-To: <8D15DE5531A8822-27BC-8EBC@webmail-m293.sysops.aol.com> X-Spam-Score: -0.7 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Markus, Right. But 8m gives a secure distance above ground regarding the visibility of the wire. 2.5m would work as well but then everybody can see it (easier). And some m above ground allows to use the wire for some other games, such as a LF dipole (TX!) or a LF 3 Lambda long wire or what ever :-) [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [74.125.82.177 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (73dk7fc[at]googlemail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 4007433f91838c822ced221546b88d5a Subject: Re: LF: VLF in Canada - earth loop Content-Type: multipart/alternative; boundary="------------000001030906020108010609" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=FROM_HAS_MIXED_NUMS,HTML_20_30, 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 This is a multi-part message in MIME format. --------------000001030906020108010609 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Markus, Right. But 8m gives a secure distance above ground regarding the visibility of the wire. 2.5m would work as well but then everybody can see it (easier). And some m above ground allows to use the wire for some other games, such as a LF dipole (TX!) or a LF 3 Lambda long wire or what ever :-) 73, Stefan Am 24.06.2014 19:03, schrieb Markus Vester: > Stefan, Joe > > I think that 8m above ground should be fine for any tests :-) > well (apart from practical reasons like people tripping over it), you > might just as well lay the (insulated) wire on the ground. > From receive measurements with your earlier and shorter earth antenna, > we deduced a depth of return current of 29 meters at 23.4 kHz, which > would scale to about 48 m at 8.3 kHz. Thus a two kilometer long > earth antenna would have the same radiation resistance (0.35 milliohm) > as a 17 m high top-loaded vertical. But skin depth and efficiency > might be greater for very low ground conductance. > Best 73, > Markus > -----Ursprüngliche Mitteilung----- > Von: Markus Vester > An: rsgb_lf_group > Verschickt: Mi, 21 Jul 2010 9:07 pm > Betreff: VLF: RE: DLF passive received with earth antenna > ... > Thus the effective height of the 280 m long earth antenna was > heff = U/E = 3.97 m at 23.4 kHz, > giving a ground loop area > A = heff * lambda/2pi = 8090 m^2, > and an effective return current depth > d = heff /length = 29 m. > This depth appears to be much less than half of the baseline length, > so it is probably indeed skin effect limited. Scaling the 23.4 kHz > results to 9 kHz would give 1.6 times more skin depth, but 1.6 times > less effective height (ie. 2.5 m) due to the larger wavelength to loop > length ratio. Thus the transmit efficiency at 9 kHz would be about 26 > dB less than that of a 100 m kite antenna with similar loss resistance. > ... > > -----Ursprüngliche Mitteilung----- > Von: DK7FC <73dk7fc@googlemail.com> > An: rsgb_lf_group > Verschickt: Di, 24 Jun 2014 3:05 pm > Betreff: Re: LF: VLF in Canada > > Oh yes, Joe, if you have plenty of forest where you can play VLF > games, i would also play with a dipole antenna. That's what i said to > Laurence a few months ago. Just install a dipole with say 10 km > length, adding 100m each day and see how the performance increases. > This will be an interesting project :-) > Maybe you remember my 700m long earth antenna which allowed me to be > copied in 45 km distance in 4.5 mHz FFT BW, back in 2011 :-) Someone > removed the antenna completely but if you have more space, just give > it a try. I think that 8m above ground should be fine for any tests :-) > > Nice to think about it :-) > > 73, GL, Stefan > > Am 24.06.2014 12:55, schrieb Markus Vester: >> Joe, good to read this! >> Regarding the loading coil, I would agree with Stefan that a large >> multiturn air coil is the best option. A laminated iron core would >> suffer from excessive eddy current losses, and the effect of ferrites >> is limited by saturation and hysteresis losses. >> My 1.3 henry coil consumed 2.3 km of 0.4 mm enameled wire, using 7 >> buckets with 480 turns on each: >> df6nm.bplaced.net/VLF/VLF_110304-06/coil_legospacers.jpg. >> The advantage is that due to magnetic coupling between layers, you >> will need less wire for a given inductance. And the inductance is >> adjustable across a wide range, using spacers. Disadvantages are the >> high electric field between layers limiting voltage capability, and >> less effective heat removal from the inner buckets. Stuffing the >> buckets too tightly into one another is surely not a good idea: >> df6nm.bplaced.net/VLF/pictures/arced_coil_140601.jpg >> An nonresonant earth antenna across high resistivity rock could also >> radiate moderately well, avoiding coil making and high voltage issues >> altogether. But to compete with your vertical in terms of radiation >> resistance, it would need to be really long, on the order of a couple >> of miles. It will have magnetic loop directional pattern which may be >> a disadvantage. >> For a transatlantic detection eg. by Paul Nicholson, a Rubidium or >> GPS locked signal source would be very beneficial. Using SpecLab with >> 1pps phase lock to eliminate soundcard output glitches has worked >> well for DJ8WX, PA1SDB, and myself. >> Best of luck, >> Markus (DF6NM) >> >> >> -----Ursprüngliche Mitteilung----- >> Von: DK7FC <73dk7fc@googlemail.com> >> An: rsgb_lf_group >> >> Verschickt: Di, 24 Jun 2014 12:48 am >> Betreff: Re: LF: VLF in Canada >> >> >> Hi Joe, Fine to hear that you're give it a try. Please, don't ask Industry Canada if the 10mW is RF power of ERP! To get out a real signal on VLF, there is no alternative to a real large coil without ferrites! Think about the high voltages... But 100m of antenna wire is a good start. I remember 550 mH for my 100m kite antenna. For me it was 2000m of 0.4mm diameter wire :-) Nice work is that. Takes long but is a funny game :-) 73, GL, Stefan Am 23.06.2014 21:33, schriebjcraig@mun.ca : Dear Group, >> I tried again to get an LOA for VLF. This time, the response from Industry Canada was favourable: 10 mW 8.0-8.3 kHz. Yesterday, after a few slight rf burns, and thanks to PA0RDT's miniwhip design and DL4YHF's Spectrum Lab and advice, VLF sigs on 8.277 kHz were heard at 200m from the 100m wire aerial. This was a reception outside my back yard! 10 watts from an 1970's keyboard amp (volume control set on 3) were stepped up with an xfmr to a lossy 500 ohm tuning coil peaked with a ferrite rod for maximum squeal at L=0.35 H. >> Is it possible for someone who is not especially enthralled by winding a mile of 0.7mm wire to use an iron core to make a VLF tuning coil? >> 73 Joe VO1NA --------------000001030906020108010609 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Markus,

Right. But 8m gives a secure distance above ground regarding the visibility of the wire. 2.5m would work as well but then everybody can see it (easier). And some m above ground allows to use the wire for some other games, such as a LF dipole (TX!) or a LF 3 Lambda long wire or what ever :-)

73, Stefan

Am 24.06.2014 19:03, schrieb Markus Vester:
Stefan, Joe
 
> I think that 8m above ground should be fine for any tests :-)
well (apart from practical reasons like people tripping over it), you might just as well lay the (insulated) wire on the ground.
 
From receive measurements with your earlier and shorter earth antenna, we deduced a depth of return current of 29 meters at 23.4 kHz, which would scale to about 48 m at 8.3 kHz. Thus a two kilometer long earth antenna would have the same radiation resistance (0.35 milliohm) as a 17 m high top-loaded vertical. But skin depth and efficiency might be greater for very low ground conductance.
 
Best 73,
Markus
 
-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 21 Jul 2010 9:07 pm
Betreff: VLF: RE: DLF passive received with earth antenna
...
 
Thus the effective height of the 280 m long earth antenna was
 heff = U/E = 3.97 m at 23.4 kHz,
giving a ground loop area
 A = heff * lambda/2pi = 8090 m^2,
and an effective return current depth
 d = heff /length = 29 m.
 
This depth appears to be much less than half of the baseline length, so it is probably indeed skin effect limited. Scaling the 23.4 kHz results to 9 kHz would give 1.6 times more skin depth, but 1.6 times less effective height (ie. 2.5 m) due to the larger wavelength to loop length ratio. Thus the transmit efficiency at 9 kHz would be about 26 dB less than that of a 100 m kite antenna with similar loss resistance.
...

-----Ursprüngliche Mitteilung-----
Von: DK7FC <73dk7fc@googlemail.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di, 24 Jun 2014 3:05 pm
Betreff: Re: LF: VLF in Canada

Oh yes, Joe, if you have plenty of forest where you can play VLF games, i would also play with a dipole antenna. That's what i said to Laurence a few months ago. Just install a dipole with say 10 km length, adding 100m each day and see how the performance increases. This will be an interesting project :-)
Maybe you remember my 700m long earth antenna which allowed me to be copied in 45 km distance in 4.5 mHz FFT BW, back in 2011 :-) Someone removed the antenna completely but if you have more space, just give it a try. I think that 8m above ground should be fine for any tests :-)

Nice to think about it :-)

73, GL, Stefan

Am 24.06.2014 12:55, schrieb Markus Vester:
Joe, good to read this!
 
Regarding the loading coil, I would agree with Stefan that a large multiturn air coil is the best option. A laminated iron core would suffer from excessive eddy current losses, and the effect of ferrites is limited by saturation and hysteresis losses.
 
My 1.3 henry coil consumed 2.3 km of 0.4 mm enameled wire, using 7 buckets with 480 turns on each:
df6nm.bplaced.net/VLF/VLF_110304-06/coil_legospacers.jpg.
The advantage is that due to magnetic coupling between layers, you will need less wire for a given inductance. And the inductance is adjustable across a wide range, using spacers. Disadvantages are the high electric field between layers limiting voltage capability, and less effective heat removal from the inner buckets. Stuffing the buckets too tightly into one another is surely not a good idea:
df6nm.bplaced.net/VLF/pictures/arced_coil_140601.jpg
 
An nonresonant earth antenna across high resistivity rock could also radiate moderately well, avoiding coil making and high voltage issues altogether. But to compete with your vertical in terms of radiation resistance, it would need to be really long, on the order of a couple of miles. It will have magnetic loop directional pattern which may be a disadvantage.
 
For a transatlantic detection eg. by Paul Nicholson, a Rubidium or GPS locked signal source would be very beneficial. Using SpecLab with 1pps phase lock to eliminate soundcard output glitches has worked well for DJ8WX, PA1SDB, and myself.
 
Best of luck,
Markus (DF6NM)


-----Ursprüngliche Mitteilung-----
Von: DK7FC <73dk7fc@googlemail.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di, 24 Jun 2014 12:48 am
Betreff: Re: LF: VLF in Canada


Hi Joe,      Fine to hear that you're give it a try. Please, don't ask Industry    Canada if the 10mW is RF power of ERP!      To get out a real signal on VLF, there is no alternative to a real large    coil without ferrites! Think about the high voltages... But 100m of    antenna wire is a good start. I remember 550 mH for my 100m kite    antenna. For me it was 2000m of 0.4mm diameter wire :-) Nice work is    that. Takes long but is a funny game :-)      73, GL, Stefan      Am 23.06.2014 21:33, schrieb jcraig@mun.ca:   Dear Group,   
I tried again to get an LOA  for VLF.  This time, the response from    Industry Canada was favourable: 10 mW 8.0-8.3 kHz.  Yesterday, after a    few slight rf burns, and  thanks to PA0RDT's miniwhip design and    DL4YHF's Spectrum Lab and advice, VLF sigs on 8.277 kHz were heard at    200m from the 100m wire aerial. This was a reception outside my back    yard!  10 watts from an 1970's keyboard amp (volume control set on 3)    were stepped up with an xfmr to a lossy 500 ohm tuning coil peaked    with a ferrite rod for maximum squeal at L=0.35 H.   
Is it possible for someone who is not especially enthralled by winding   a mile of 0.7mm wire to use an iron core to make a VLF tuning coil?   
73   Joe VO1NA
--------------000001030906020108010609--