Return-Path: Received: from mtain-di05.r1000.mx.aol.com (mtain-di05.r1000.mx.aol.com [172.29.64.9]) by air-dc09.mail.aol.com (v129.4) with ESMTP id MAILINDC094-86a74d8498047a; Sat, 19 Mar 2011 07:48:20 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-di05.r1000.mx.aol.com (Internet Inbound) with ESMTP id C49E038000213; Sat, 19 Mar 2011 07:48:10 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q0ucq-0003g3-F8 for rs_out_1@blacksheep.org; Sat, 19 Mar 2011 11:47:20 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q0ucp-0003fu-Kw for rsgb_lf_group@blacksheep.org; Sat, 19 Mar 2011 11:47:19 +0000 Received: from mail-iw0-f171.google.com ([209.85.214.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q0ucn-0003l5-0i for rsgb_lf_group@blacksheep.org; Sat, 19 Mar 2011 11:47:19 +0000 Received: by iwr19 with SMTP id 19so6443725iwr.16 for ; Sat, 19 Mar 2011 04:47:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=7Kiqvji+fIsaKmTJjuYICvSBf0dYWnrGAUSvXR1M/m8=; b=rHrA5bo5E0ZHvhy+bMjVrpkoLpFvxRNbGBLWiD7grRswhAOYPij1e8TPKORF5hr9J5 OE2QakMIfjKcB3MDao8tk+q9J4PGpJQPEoaIoBvEUmNpAyHlOg4BHB7dsGtn9tg8KPnx xFSi6MrgtH26qgMOrZ58AkdiYcyEUXQGPX5qo= 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=dbHGncCb4UdmBZhWcFD5KTt5DQrInGiLWcyziuDB4kG3DTj/fL2CRZkyyw0jx4Kru9 BXK8zulocSEMuUQ9C9WmQj256hL24ufQerucgQGsuRnZDWgLZGbo5OH+0mkC7YioZlZJ wWNAbsccvRXYSs/YolRJ3D6cXmlzNTbFfRg3o= MIME-Version: 1.0 Received: by 10.43.131.201 with SMTP id hr9mr3431712icc.53.1300535229823; Sat, 19 Mar 2011 04:47:09 -0700 (PDT) Received: by 10.42.189.74 with HTTP; Sat, 19 Mar 2011 04:47:09 -0700 (PDT) In-Reply-To: <000b01cbe622$6a23f8d0$8d01a8c0@JAYDELL> References: <4D83D475.9090609@telus.net> <000b01cbe622$6a23f8d0$8d01a8c0@JAYDELL> Date: Sat, 19 Mar 2011 11:47:09 +0000 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.3 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,MAILTO_TO_SPAM_ADDR=0.276 Subject: Re: LF: Loop TX antennas at VLF? Content-Type: multipart/alternative; boundary=20cf307f34c8643946049ed4746c X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.6 required=5.0 tests=HTML_20_30, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE,MAILTO_TO_SPAM_ADDR 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-d021.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d40094d8497fa7d7d X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --20cf307f34c8643946049ed4746c Content-Type: text/plain; charset=ISO-8859-1 Rik, et al Actually I am beginning to think that this small VLF TX loop is not such a totally daft idea after all. The main issue seems to be with the capacitors but these seem to be less onerous than winding a very big (and lossy) coil. Certainly there sounds to be merit in a larger TX loop for /P operation. Thanks everyone for the constructive feedback on this thread. Most interesting. 73s Roger G3XBM On 19 March 2011 10:42, wrote: > Rik, Roger, Jim, Mal > > There are soil losses to consider with the loop as well. At 185 kHz (Part > 15 lowfer band), I ran a 50' X 50' transmitting loop made from mil spec > RG-11 (copper braid) and the soil losses were about equal to the wire > losses. Not sure what the soil loss would be at 9 kHz but it would be > interesting to know. > > Jay W1VD WD2XNS WE2XGR/2 > > > > ----- Original Message ----- > *From:* Rik Strobbe > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Saturday, March 19, 2011 6:07 AM > *Subject:* RE: LF: Loop TX antennas at VLF? > > Roger, > > as Jim calculated running 100W in a 10 x 10 m loop will give about 0.5uW > ERP (is you use 4 x 1.5mm wire in parallel instead of a single 3mm wire in > order to avoid skinn effect losses). Using more parallel wires of a coax > cable might pump up the ERP to 1 or 2uW. > > Looks pretty poor, but will a vertical antenna of a similar size do better > ? > > At 9kHz the radiation resistance of a 10m high + 10m topload vertical > 75uOhm. > The antenna capacitance is 110pF, a reactance of 161kOhm. What means that > you will need a loading coil of 2.84H (yep Henry). Apart from the fact that > it will cost a lot on copper wire the coil losses will be high. You will > need a Q of 160 to reduce the losses to 1kOhm. In addition for such a small > antenna you can excpect several 100 Ohm ground loss, so let's assume a total > loss of 1500 Ohm. 100W TX power will result in about 0.25 A antenna current > and an ERP of about 8uW. > That's 6 to 10dB better than the loop, but instead of some cheap cap's you > will need a monster coil. I ran it one on the online coil calculators and it > came up to a 2.5m high and 1.8m diameter coil with amost 10km of 1.5mm Cu > wire (weight 150kg). And running 0.25A into the antenna will result in 40kV > ! > > So, despite the vertical could be 10dB better than the loop, the loop seems > much more easy (and cheap) to build. > It might be easier and cheaper to get the extra 10dB by usung mor wire in > the loop and pump up the power. > > 73, Rik ON7YD - OR7T > > > ------------------------------ > *Van:* owner-rsgb_lf_group@blacksheep.org [ > owner-rsgb_lf_group@blacksheep.org] namens Roger Lapthorn [ > rogerlapthorn@gmail.com] > *Verzonden:* vrijdag 18 maart 2011 23:02 > *Aan:* rsgb_lf_group@blacksheep.org > *Onderwerp:* Re: LF: Loop TX antennas at VLF? > > Yep, I guess you're right Scott. And you know better than most. Ah well, > it was an interesting idea to toss around. > > 73s > Roger G3XBM > > On 18 March 2011 21:53, Scott Tilley wrote: > >> Hi Roger >> >> The practicality of pumping 35A into a loop is not an easy task! Couple >> this with the stability of most capacitors creates a real engineering >> challenge for a loop on 9KHz, notE the BW and Q. Not to mention really low >> ERP one would get. >> >> This will be an engineering challenge for sure! >> >> 73 Scott >> VE7TIL >> >> >> On 3/18/2011 2:39 PM, Roger Lapthorn wrote: >> >> Hi All >> >> Just run Andy's spreadsheet for magnetic loops to see the sort of figures >> we get at 8.9kHz. Assuming 100W and a loop diameter of 10m with 3mm wire the >> efficiency works out at -87.4dB and the ERP -67.4dBW (0.2uW). There is also >> the matter of the low loss 6211.7nF capacitor. With larger loop diameters, >> thicker wire (or multiple paralleled wires) and maybe 200W then the ERPs are >> starting to get more useful. >> >> The Marconi does seem a better bet, even with all the issues with losses >> in the huge loading coil, but a VLF TX loop doesn't look a total "no-hope" >> approach. Larger loops, with improved efficiencies, may be easier than kite >> or balloon supported ones in a /P location. >> >> And then there is the widely spaced earthed electrode antenna..... but I >> won't start a discussion on the merits or otherwise of this as I am about to >> go on holiday this weekend and will not be able to respond to emails next >> week. We know from work by DK7FC (and VLF professionals) that this does work >> as a radiating structure. >> >> 73s >> Roger G3XBM >> >> >> >> On 18 March 2011 14:09, Roger Lapthorn wrote: >> >>> Just wondering if anyone has done the maths to work out what sort of ERP >>> could be expected at 8.97kHz with, say, 100W to a smallish loop antenna in >>> the garden? >>> >>> It would certainly avoid the need for very very large matching coils and >>> may be easier to engineer than a Marconi. Even an efficiency of -80dB would >>> allow 1uW ERP and, judging by results from G3XIZ with around 2uW, this could >>> be useful with long stable carrier transmissions of several hours. Most of >>> us could run a loop with an area of 100sq m. with thickish wire in our >>> gardens. A loop might also be more practical for portable operations perhaps >>> with a triangle with one high support. >>> >>> Certainly my own results with WSPR at 136 and 500kHz with just a few >>> watts and quite thin wire and around 80sq m loop area were encouraging. Mind >>> you, 9kHz is very much lower than 136kHz, so the radiation resistance would >>> be tiny I assume. >>> >>> 73s >>> Roger G3XBM >>> >>> -- >>> http://g3xbm-qrp.blogspot.com/ >>> http://www.g3xbm.co.uk >>> http://www.youtube.com/user/g3xbm >>> https://sites.google.com/site/sub9khz/ >>> G3XBM GQRP 1678 ISWL G11088 >>> >> >> >> >> -- >> http://g3xbm-qrp.blogspot.com/ >> http://www.g3xbm.co.uk >> http://www.youtube.com/user/g3xbm >> https://sites.google.com/site/sub9khz/ >> G3XBM GQRP 1678 ISWL G11088 >> >> >> > > > -- > http://g3xbm-qrp.blogspot.com/ > http://www.g3xbm.co.uk > http://www.youtube.com/user/g3xbm > https://sites.google.com/site/sub9khz/ > G3XBM GQRP 1678 ISWL G11088 > > -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm https://sites.google.com/site/sub9khz/ G3XBM GQRP 1678 ISWL G11088 --20cf307f34c8643946049ed4746c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Rik, et al

Actually I am beginning to think that this small VLF TX= loop is not such a totally daft idea after all. The main issue seems to= be with the capacitors but these seem to be less onerous than winding a= very big (and lossy) coil. Certainly there sounds to be merit in a larger= TX loop for /P operation.

Thanks everyone for the constructive feedback on this thread. Most int= eresting.

73s
Roger G3XBM

On= 19 March 2011 10:42, <jrusgrove@comcast.net> wrote:
Rik, Roger, Jim, Mal
=A0
There are soil losses to consider wit= h the loop as=20 well. At 185 kHz (Part 15 lowfer band),=A0I ran a 50' X 50' transm= itting loop=20 made from=A0mil spec RG-11 (copper braid) and the soil losses were about= =20 equal to the wire losses. Not sure what the soil loss would be at 9 kHz bu= t it=20 would be interesting to know.=A0
=A0
Jay W1VD=A0 WD2XNS=A0=20 WE2XGR/2=A0=A0=A0
=A0
=A0
----- Original Message -----
From:=20 Rik Strobbe
Sent: Saturday, March 19, 2011= 6:07=20 AM
Subject: RE: LF: Loop TX antenna= s at=20 VLF?

Roger,
=A0
as Jim calculated running 100W in= a 10 x 10 m=20 loop will give about 0.5uW ERP (is you use 4 x 1.5mm wire in parallel in= stead=20 of a single 3mm wire in order to avoid skinn effect losses). Using more= =20 parallel wires of a coax cable might pump up the ERP to 1 or 2uW.=
=A0
Looks pretty poor, but will a vert= ical antenna=20 of a similar size do better ?
=A0
At 9kHz the radiation resistance= of a 10m high +=20 10m topload vertical 75uOhm.
The antenna capacitance is 110pF,= a reactance of=20 161kOhm. What means that you will need a loading coil of 2.84H (yep Henr= y).=20 Apart from the fact that it will cost a lot on copper wire the coil loss= es=20 will be high. You will need a Q of 160 to reduce the losses to 1kOhm. In= =20 addition for such a small antenna you can excpect=A0several 100 Ohm grou= nd=20 loss, so let's assume=A0a total loss of 1500 Ohm. 100W TX power will= result=20 in about 0.25 A antenna current and an ERP of about 8uW.
That's 6 to 10dB better than the loop, but instead of some chea= p cap's=20 you will need a monster coil. I ran it one on the online coil=20 calculators=A0and it came up to a 2.5m high and 1.8m diameter coil with= =20 amost 10km of 1.5mm Cu wire (weight 150kg). And running 0.25A into the= antenna=20 will result in 40kV !
=A0
So, despite the vertical could be= 10dB better=20 than the loop, the loop seems much more easy (and cheap) to=20 build.
It might be easier and cheaper to= get the extra=20 10dB by usung mor wire in the=A0loop and pump up the power.
=A0
73, Rik=A0 ON7YD - OR7T=A0<= /div>
=A0
=A0
Van:=20 = owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens=20 Roger Lapthorn [rogerlapthorn@gmail.com]
Verzonden: vrijdag 18 maart=20 2011 23:02
Aan: rsgb_lf_group@blacksheep.org
Onderwerp:= =20 Re: LF: Loop TX antennas at VLF?

Yep, I guess you're right Scott. And you know better than most.= =A0 Ah=20 well, it was an interesting idea to toss around.

73s
Roger=20 G3XBM

On 18 March 2011 21:53, Scott Tilley <sthe= d475@telus.net> wrote:
Hi Roger

The practicality of pumping= 35A into=20 a loop is not an easy task!=A0 Couple this with the stability of most= =20 capacitors creates a real engineering challenge for a loop on 9KHz, no= tE the=20 BW and Q.=A0 Not to mention really low ERP one would get.=A0=20

This will be an engineering challenge for sure!

73=20 Scott
VE7TIL=20


On 3/18/2011 2:39 PM, Roger Lapthorn wrote:=20
Hi All

Just run Andy's spreadshee= t for=20 magnetic loops to see the sort of figures we get at 8.9kHz. Assuming= 100W=20 and a loop diameter of 10m with 3mm wire the efficiency works out at= =20 -87.4dB and the ERP -67.4dBW (0.2uW). There is also the matter of th= e low=20 loss 6211.7nF capacitor. With larger loop diameters, thicker wire (o= r=20 multiple paralleled wires) and maybe 200W then the ERPs are starting= to=20 get more useful.=A0

The Marconi does seem a better bet, even= =20 with all the issues with losses in the huge loading coil, but a VLF= TX=20 loop doesn't look a total "no-hope" approach. Larger= loops, with improved=20 efficiencies, may be easier than kite or balloon supported ones in= a /P=20 location.

And then there is the widely spaced earthed electr= ode=20 antenna..... but I won't start a discussion on the merits or oth= erwise of=20 this as I am about to go on holiday this weekend and will not be abl= e to=20 respond to emails next week. We know from work by DK7FC (and VLF=20 professionals) that this does work as a radiating structure.=20

73s
Roger G3XBM



On 18 March 2011 14:09, Roger Lapthorn <rogerlapthorn@gmail.com>=20 wrote:
Just=20 wondering if anyone has done the maths to work out what sort of ER= P=20 could be expected at 8.97kHz with, say, 100W to a smallish loop an= tenna=20 in the garden?

It would certainly avoid the need for very= very=20 large matching coils and may be easier to engineer than a Marconi.= Even=20 an efficiency of -80dB would allow 1uW ERP and, judging by results= from=20 G3XIZ with around 2uW, this could be useful with long stable carri= er=20 transmissions of several hours. Most of us could run a loop with= an area=20 of 100sq m. with thickish wire in our gardens. A loop might also= be more=20 practical for portable operations perhaps with a triangle with one= high=20 support.

Certainly my own results with WSPR at 136 and 500k= Hz=20 with just a few watts and quite thin wire and around 80sq m loop= area=20 were encouraging. Mind you, 9kHz is very much lower than 136kHz,= so the=20 radiation resistance would be tiny I assume.

73s
Roger= =20 G3XBM

--
http://g3xbm-qrp.blo= gspot.com/
htt= p://www.g3xbm.co.uk
http://www= .youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
G3= XBM=A0=A0=20 GQRP 1678=A0=A0=A0 ISWL=20 G11088



-- http://g3xbm= -qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www= .youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
G3= XBM=A0=A0=20 GQRP 1678=A0=A0=A0 ISWL=20 G11088



--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www= .youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
G3XBM=A0=A0 GQRP=20 1678=A0=A0=A0 ISWL G11088



--
http://g3xbm-qrp.blogspot.com/<= br>http://www.g3xbm.c= o.uk
http://www= .youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
G3XBM=A0=A0 GQRP 1678= =A0=A0=A0 ISWL G11088
--20cf307f34c8643946049ed4746c--