Return-Path: Received: from mtain-dk06.r1000.mx.aol.com (mtain-dk06.r1000.mx.aol.com [172.29.180.10]) by air-me01.mail.aol.com (v129.4) with ESMTP id MAILINME012-8ba14d86bdcaed; Sun, 20 Mar 2011 22:54:02 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 6347838000094; Sun, 20 Mar 2011 22:54:00 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q1VEX-00018U-13 for rs_out_1@blacksheep.org; Mon, 21 Mar 2011 02:52:41 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q1VEV-00018L-J2 for rsgb_lf_group@blacksheep.org; Mon, 21 Mar 2011 02:52:39 +0000 Received: from outbound04.telus.net ([199.185.220.223] helo=defout.telus.net) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q1VES-0002VA-LR for rsgb_lf_group@blacksheep.org; Mon, 21 Mar 2011 02:52:39 +0000 Received: from edtncm04 ([199.185.220.240]) by priv-edtnes24.telusplanet.net (InterMail vM.8.01.03.00 201-2260-125-20100507) with ESMTP id <20110321025233.GZPR29925.priv-edtnes24.telusplanet.net@edtncm04> for ; Sun, 20 Mar 2011 20:52:33 -0600 Received: from [192.168.1.74] ([75.157.141.251]) by edtncm04 with bizsmtp id MesX1g01h5Reinf01esYEV; Sun, 20 Mar 2011 20:52:33 -0600 X-Telus-Outbound-IP: 75.157.141.251 X-Authority-Analysis: v=1.1 cv=z142bJkMWqDP2XEzlxQnuwIoOh3xLk/o5216ri01DCg= c=1 sm=2 a=jVez_htjv6wA:10 a=4aPOdFJL9SoA:10 a=F3M5lZpKAAAA:8 a=pGLkceISAAAA:8 a=C_IRinGWAAAA:8 a=aatUQebYAAAA:8 a=fnYqA7hvAAAA:8 a=j6Q1dnSHAAAA:8 a=A06HpNCPAAAA:20 a=8P0jffWtAAAA:20 a=tpBLhHfCrVQhSD2tszAA:9 a=FtZX4o3kzVxLXsBYVoIA:7 a=k_t85_WqSI-DXOLIzUMxPtVm3rsA:4 a=wPNLvfGTeEIA:10 a=wk6s2zzMB60A:10 a=MSl-tDqOz04A:10 a=si9q_4b84H0A:10 a=rBKJJ2Jc0C4A:10 a=gA6IeH5FQcgA:10 a=NWVoK91CQyQA:10 a=FP-S0s8lqARTzOp3:21 a=lAwKVP6Ic3LYuS_x:21 a=waXlFQ4yRD1w2kggK5gA:9 a=DeeBhat065P1TinPjJ0A:7 a=U7VI3o2PKd93Lnd4oVFRCfdp-OAA:4 a=y-Y-7UtO32Fkrwux:21 a=58o7qoymdSYS-NpB:21 Message-ID: <4D86BD6F.8020006@telus.net> Date: Sun, 20 Mar 2011 19:52:31 -0700 From: Scott Tilley User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.15) Gecko/20110303 Lightning/1.0b2 Thunderbird/3.1.9 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <4D83D475.9090609@telus.net> <000b01cbe622$6a23f8d0$8d01a8c0@JAYDELL>, In-Reply-To: X-Spam-Score: 1.7 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,MAILTO_TO_SPAM_ADDR=0.276,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Loop TX antennas at VLF? Content-Type: multipart/alternative; boundary="------------040109080509080104050906" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.5 required=5.0 tests=FROM_ENDS_IN_NUMS,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-sid: 3039ac1db40a4d86bdc76f96 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --------------040109080509080104050906 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi Rik I think I missed a message or two. What current level is the consensus for 100W input at 9KHz into a reasonable loop? I missed how this was modeled and wonder if my original assumptions where off base. Thanks for any clarification you can offer. 73 Scott VE7TIL On 3/19/2011 9:27 AM, Rik Strobbe wrote: > Roger, > the antenna reactance about 2.5 Ohm, so the antenna voltage (and thus > capacitor voltage) will be less than 100V. > I assume that polypropylene caps that work fine on 137 and 500 will > also be OK at 9kHz. > Farnell sells 1uF/275Vac at 0.44 Euro (10 QTY) and 0.1uF/305Vac at > 0.32 Euro (10 QTY), so for less than 10 Euro you should be able to > tune the antenna in 0.1uF steps. As the antenna Q is rather low > (2.5/0.1 = 25) a 0.1uF step should be OK for a first try. > 73, Rik ON7YD - OR7T > ------------------------------------------------------------------------ > *Van:* owner-rsgb_lf_group@blacksheep.org > [owner-rsgb_lf_group@blacksheep.org] namens Roger Lapthorn > [rogerlapthorn@gmail.com] > *Verzonden:* zaterdag 19 maart 2011 12:47 > *Aan:* rsgb_lf_group@blacksheep.org > *Onderwerp:* Re: LF: Loop TX antennas at VLF? > > 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 --------------040109080509080104050906 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Rik

I think I missed a message or two.  What current level is the consensus for 100W input at 9KHz into a reasonable loop?  I missed how this was modeled and wonder if my original assumptions where off base.

Thanks for any clarification you can offer.

73 Scott
VE7TIL



On 3/19/2011 9:27 AM, Rik Strobbe wrote:
Roger,
 
the antenna reactance about 2.5 Ohm, so the antenna voltage (and thus capacitor voltage) will be less than 100V.
I assume that polypropylene caps that work fine on 137 and 500 will also be OK at 9kHz.
Farnell sells 1uF/275Vac at 0.44 Euro (10 QTY) and 0.1uF/305Vac at 0.32 Euro (10 QTY), so for less than 10 Euro you should be able to tune the antenna in 0.1uF steps. As the antenna Q is rather low (2.5/0.1 = 25) a 0.1uF step should be OK for a first try.
 
73, Rik  ON7YD - OR7T
 
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger Lapthorn [rogerlapthorn@gmail.com]
Verzonden: zaterdag 19 maart 2011 12:47
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: Loop TX antennas at VLF?

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, <jrusgrove@comcast.net> 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 -----
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 <sthed475@telus.net> 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 <rogerlapthorn@gmail.com> 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

--------------040109080509080104050906--