Return-Path: Received: from mtain-me01.r1000.mx.aol.com (mtain-me01.r1000.mx.aol.com [172.29.96.137]) by air-dd09.mail.aol.com (v129.4) with ESMTP id MAILINDD094-86b14d8480a86a; Sat, 19 Mar 2011 06:08:40 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-me01.r1000.mx.aol.com (Internet Inbound) with ESMTP id B588338000110; Sat, 19 Mar 2011 06:08:32 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q0t46-0002jU-9P for rs_out_1@blacksheep.org; Sat, 19 Mar 2011 10:07:22 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q0t45-0002jL-It for rsgb_lf_group@blacksheep.org; Sat, 19 Mar 2011 10:07:21 +0000 Received: from cavuit02.kulnet.kuleuven.be ([134.58.240.44]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q0t42-00022t-0A for rsgb_lf_group@blacksheep.org; Sat, 19 Mar 2011 10:07:21 +0000 Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit02.kulnet.kuleuven.be (Postfix) with ESMTP id 4C89C51C005 for ; Sat, 19 Mar 2011 11:07:10 +0100 (CET) Received: from ICTS-S-HUB-N2.luna.kuleuven.be (icts-s-hub-n2.luna.kuleuven.be [10.112.9.12]) by smtps01.kuleuven.be (Postfix) with ESMTP id 36E9931E702 for ; Sat, 19 Mar 2011 11:07:10 +0100 (CET) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N2.luna.kuleuven.be ([10.112.9.12]) with mapi; Sat, 19 Mar 2011 11:07:10 +0100 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Sat, 19 Mar 2011 11:07:09 +0100 Thread-Topic: LF: Loop TX antennas at VLF? Thread-Index: AcvluIYyLGlh8aalRmCthpwggDCY7gAXdFy7 Message-ID: References: <4D83D475.9090609@telus.net>, In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be 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="_000_BF4A524700075746A6467658DFC7102C88B2129D4CICTSSEXC2CAlu_" 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, TO_ADDRESS_EQ_REAL 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-sid: 3039ac1d60894d8480a06be1 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C88B2129D4CICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 co= ax 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 75uO= hm. 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 th= at it will cost a lot on copper wire the coil losses will be high. You wil= l need a Q of 160 to reduce the losses to 1kOhm. In addition for such a sm= all 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 anten= na 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 seem= s 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.or= g] 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 cha= llenge 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 the= n 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 wou= ld 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 operatio= ns 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 yo= u, 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 --_000_BF4A524700075746A6467658DFC7102C88B2129D4CICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
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 pa= rallel 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 vertic= al 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 2.8= 4H (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 sma= ll antenna you can excpect several 100 Ohm ground loss, so let's assu= me 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 calculator= s and it came up to a 2.5m high and 1.8m diameter coil with amost 10k= m of 1.5mm Cu wire (weight 150kg). And running 0.25A into the antenna will result in 40kV !
 
So, despite the vertical could be 10= dB better than the loop, the loop seems much more easy (and cheap) to buil= d.
It might be easier and cheaper to ge= t the extra 10dB by usung mor wire in the loop and pump up the power.=
 
73, Rik  ON7YD - OR7T&nb= sp;
 
 
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&= gt; wrote:
Hi Roger

The practicality of pumping 35A into a loop is not an easy task!  Cou= ple 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 rea= lly 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 parallel= ed wires) and maybe 200W then the ERPs are starting to get more useful.&nb= sp;

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 eas= ier 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@gma= il.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 wou= ld 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 yo= u, 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.u= k
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.u= k
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.u= k
http://www= .youtube.com/user/g3xbm
https= ://sites.google.com/site/sub9khz/
G3XBM   GQR= P 1678    ISWL G11088
--_000_BF4A524700075746A6467658DFC7102C88B2129D4CICTSSEXC2CAlu_--