Return-Path: Received: from mtain-dg09.r1000.mx.aol.com (mtain-dg09.r1000.mx.aol.com [172.29.65.17]) by air-db01.mail.aol.com (v129.4) with ESMTP id MAILINDB012-861b4d0800ca35c; Tue, 14 Dec 2010 18:42:02 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dg09.r1000.mx.aol.com (Internet Inbound) with ESMTP id 94441380001BA; Tue, 14 Dec 2010 18:38:47 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PSeRN-0000Qs-HA for rs_out_1@blacksheep.org; Tue, 14 Dec 2010 23:37:53 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PSeRM-0000Qh-IL for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 23:37:52 +0000 Received: from out1.ip09ir2.opaltelecom.net ([62.24.128.245]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PSeRK-0008L7-EH for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 23:37:52 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvsEAGuOB01cHYYR/2dsb2JhbACkG3jBS4VKBIFgjEs X-IronPort-AV: E=Sophos;i="4.59,345,1288569600"; d="scan'208,217";a="460596588" Received: from unknown (HELO xphd97xgq27nyf) ([92.29.134.17]) by out1.ip09ir2.opaltelecom.net with SMTP; 14 Dec 2010 23:37:43 +0000 Message-ID: <001b01cb9be7$e48cbb50$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <80E0204D3E534137903FE0B8E499597F@IBM7FFA209F07C> <4D0783FC.3090107@iup.uni-heidelberg.de> <4D07B3A2.80409@iup.uni-heidelberg.de> <009d01cb9bc8$73fe6f10$0401a8c0@xphd97xgq27nyf> <4D07E7CD.1090304@iup.uni-heidelberg.de> Date: Tue, 14 Dec 2010 23:37:33 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Earth Electrodes Content-Type: multipart/alternative; boundary="----=_NextPart_000_0016_01CB9BE7.E1B7F070" 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=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-sid: 3039ac1d41114d0800067975 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : temperror ------=_NextPart_000_0016_01CB9BE7.E1B7F070 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Stefan If your 600m wire is average 6 metres above the ground then you have= an elevated grounded loop whose natural resonance is the length of wi= re plus the same length earth return plus 6 m vertical at each end ie= 1200m plus 12 metres =3D=3D 1212 metres. This is an old trick used on 80m and 160m to make a vertical loop ante= nna where space is restricted. ie one half of the antenna is elevated= above ground and the other half is made up by the ground, and can be= in the form of a rectangle or square or triangle. Half the rectangle= or square or triangle is elevated normally as high as possible above= ground and the ground is a MIRROR image to complete the loop.=20 An earth mode antenna is the type of antenna used by the CAVE fraterni= ty to communicate through ground ie below ground in a CAVE to the grou= nd above.=20 ie short distance communications. In my opinion an earth mode antenna is intended to communicate short= distances EARTH to EARTH, TX into the earth using a probe rod and RX= this signal=20 using another probe rod . Your grounded loop is propagating the signal= into the ether with the intention of it being received by an elevated= RX antenna some hundreds of metres or Kilometres away at a distant lo= cation.=20 de mal/g3kev ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, December 14, 2010 9:55 PM Subject: Re: LF: Earth Electrodes Mal, No. It depends on the frequency. On 8970 Hz and lower it is an earth ant= enna.=20 Mal, it was so often explained how an earth antenna works. Do we rea= lly have to repeat that each few weeks? Really? OK, once again: And earth electrode antenna is a loop antenna where the current retu= rn path is in the earth. So there are two electrodes and the TX can be= applied anywhere between these two electrodes. Furthermore i have nev= er said to have 2 wires (600m each) but just one wire. The TX ground= is connected to the first (near) ground rod(s) and the center of the= coax is applied to the wire which is in 6m height (average). The tota= l wire length is about 700m and the electrode spacing is about 600m.= So the far away electrode is in 600m distance.=20 Rogers and my earth antenna is not a grounded loop antenna since the= wire is not closed! The ground is a part of the loop, thats the diffe= rence between a usual loop and an earth antenna. I can run a current at any frequency. I have tried 10 Hz (just for= testing) and DC and 100 Hz and so on. I hope you can agree that the= current MUST come back trough the ground if the frequency is 0 (DC)!!= So, the lower the conductivity, the higher the effective area of the= loop (skin effect!!!) and thus the efficiency. Since i am on a hill= there (500m ASL) and there are almost only stones, the conductivity= is very low. This causes more effort in arranging a suitable earth ro= d system ( i am using 30 rods, 0.4m long each, spaced about 1m) but is= is interesting :-) There is no matching from 8 Ohm to 50 Ohm since my PA has not an out= put impedance of 8 Ohm and my antenna has not an input impedance of 50= Ohm ;-) The goal is to get as much antenna current as possible, so there is= no need to match something to 50 Ohm. Since the cable length is alway= s <<< Lambda, there is no need to match something! I can measure the= antenna current directly by using a digital multimeter(attached pictu= re). The power can be measured on the DC side of the PA, since the eff= iciency is quasi 100%. So you can calculate the losses. If the earth antenna has a overall resistance of 500 Ohm and you can= and want to generate 500 W (assuming the reactive Z component is negl= igible) you just have to apply 500 V (rms) on the wire, thats all! Earth antenna does not mean that the wire is on the ground but that= the current comes back in the earth!=20 So, hope to have answered the questions, in december. 73, Stefan Am 14.12.2010 20:52, schrieb mal hamilton:=20 Stefan You now admit that your antenna is in FACT a LOSSY DIPOLE and not= an earth antenna g3kev ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, December 14, 2010 6:12 PM Subject: Re: LF: Earth Electrodes Chris, LF, Am 14.12.2010 17:27, schrieb Chris:=20 HiStefan, Yes, but 600m is VERY long! The wire even laying on the ground= I would expect to radiate quite well at 137 with that length! And how= many watts?? ERP?? I am sure 8970 would do well through the ground at the sort of= powers being spoken about. Probably ideal for submarines, as Roger sa= ys! Vy 73, Chris, G4AYT. Well, my earth antenna is grounded at the ends and TX power was= about 250 W. The mode was DFCW-600. The receiver was at Michael Oexne= r using a PA0RDT design. ERP? No idea, probably some few uW. Its not= so easy to calculate the losses. Yes, on 137 kHz the wire length comes close to lambda/4 and abov= e so it acts not just like a pure earth antenna but rather as a combin= ation of this and a very loss dipole. On 137, my power was 100 W at th= is test. The antenna was built to do local tests but seems to work suitab= le on 137. So it is a fixed antenna, my only fixed one. And it is a ve= ry quiet location. This makes it interesting to use it as a RX antenna= too!... 73, Stefan ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, December 14, 2010 2:49 PM Subject: Re: LF: Earth Electrodes Hi Chris, But how do you explain that i have crossed 49.6 km with a 60= 0m spaced earth electrode antenna on 8970 Hz? It was rather summer tim= e than winther (regarding QRN)! With the same antenna, my 137 kHz sign= al was seen 20 dB above noise near Paris in DFCW-3!????? 73, Stefan Am 14.12.2010 15:15, schrieb Chris:=20 Hi Mal, Yes, that is what I had concluded years ago. No harm in tr= ying though! Further to your previous e-mail to LF, looks to me like be= acons are now becoming the norm on 136/7kHz band and below. I have no= problem with that personally, indeed, I think it preferable to a QSO= taking forever! I woud like to see full idents though, no matter how= slow. Vy 73, Chris, G4AYT. ------=_NextPart_000_0016_01CB9BE7.E1B7F070 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Stefan
If your 600m wire is average 6 metres= above the=20 ground then you have an elevated grounded loop whose natural resonance= is the=20 length of wire plus the same length earth return plus 6 m vertical&nbs= p;at each=20 end ie 1200m plus 12 metres =3D=3D 1212 metres.
This is an old trick used on 80m= and 160m to=20 make a vertical loop antenna where space is restricted. ie= one half of=20 the antenna is elevated above ground and the other half is made up by= the=20 ground, and can be in the form of a rectangle or square or triang= le. Half=20 the rectangle or square or triangle is elevated normally as high as po= ssible=20 above ground and the ground is a MIRROR image to complete the loo= p.=20
 
An earth mode antenna is the type of= antenna used=20 by the CAVE fraternity to communicate through ground ie below ground= in a CAVE=20 to the ground above.
ie short distance communications.
 
In my opinion an earth mode antenna= is intended to=20 communicate short distances EARTH to EARTH, TX into the earth using a&= nbsp;probe=20 rod and RX this signal
using another probe rod . Your ground= ed loop is=20 propagating the signal into the ether with the intention of it being= received by=20 an elevated RX antenna some hundreds of metres or Kilometres away= at a=20 distant location.
 
de mal/g3kev
 
----- Original Message -----
Sent: Tuesday, December 14,= 2010 9:55=20 PM
Subject: Re: LF: Earth Electr= odes

Mal,

No.
It=20 depends on the frequency. On 8970 Hz and lower it is an earth antenn= a.=20

Mal, it was so often explained how an earth antenna works.= Do we=20 really have to repeat that each few weeks? Really? OK, once again:
And=20 earth electrode antenna is a loop antenna where the current return= path is in=20 the earth. So there are two electrodes and the TX can be applied any= where=20 between these two electrodes. Furthermore i have never said to have= 2 wires=20 (600m each) but just one wire. The TX ground is connected to the fir= st (near)=20 ground rod(s) and the center of the coax is applied to the wire whic= h is in 6m=20 height (average). The total wire length is about 700m and the electr= ode=20 spacing is about 600m. So the far away electrode is in 600m distance= .=20

Rogers and my earth antenna is not a grounded loop antenna= since the=20 wire is not closed! The ground is a part of the loop, thats the diff= erence=20 between a usual loop and an earth antenna.

I can run a curren= t at any=20 frequency. I have tried 10 Hz (just for testing) and DC and 100 Hz= and so on.=20 I hope you can agree that the current MUST come back trough the grou= nd if the=20 frequency is 0 (DC)!! So, the lower the conductivity, the higher the= effective=20 area of the loop (skin effect!!!) and thus the efficiency. Since i= am on a=20 hill there (500m ASL) and there are almost only stones, the conducti= vity is=20 very low. This causes more effort in arranging a suitable earth rod= system ( i=20 am using 30 rods, 0.4m long each, spaced about 1m) but is is interes= ting=20 :-)

There is no matching from 8 Ohm to 50 Ohm since my PA has= not an=20 output impedance of 8 Ohm and my antenna has not an input impedance= of 50 Ohm=20 ;-)
The goal is to get as much antenna current as possible, so th= ere is no=20 need to match something to 50 Ohm. Since the cable length is always= =20 <<< Lambda, there is no need to match something! I can meas= ure the=20 antenna current directly by using a digital multimeter(attached pict= ure). The=20 power can be measured on the DC side of the PA, since the efficiency= is quasi=20 100%. So you can calculate the losses.

If the earth antenna= has a=20 overall resistance of 500 Ohm and you can and want to generate 500= W (assuming=20 the reactive Z component is negligible) you just have to apply 500= V (rms) on=20 the wire, thats all!

Earth antenna does not mean that the wir= e is on=20 the ground but that the current comes back in the earth!

So,= hope to=20 have answered the questions, in december.

73, Stefan

A= m=20 14.12.2010 20:52, schrieb mal hamilton:=20
Stefan
You now admit that your antenna= is in FACT a=20 LOSSY DIPOLE and not an earth antenna
g3kev
 
-----=20 Original Message -----
Sent:=20 Tuesday, December 14, 2010 6:12 PM
Subject:=20 Re: LF: Earth Electrodes

Chris, LF,

Am 14.12.2010 17:27, schrieb Ch= ris:=20
HiStefan,
Yes, but 600m is VERY long!= The wire even=20 laying on the ground I would expect to radiate quite well at= 137 with=20 that length! And how many watts?? ERP??
I am sure 8970 would do well= through=20 the ground at the sort of powers being spoken about. Prob= ably ideal=20 for submarines, as Roger says!
Vy 73, Chris,=20 G4AYT.
Well, my earth antenna is ground= ed at the=20 ends and TX power was about 250 W. The mode was DFCW-600. The re= ceiver was=20 at Michael Oexner using a PA0RDT design. ERP? No idea, probably= some few=20 uW. Its not so easy to calculate the losses.

Yes, on 137= kHz the=20 wire length comes close to lambda/4 and above so it acts not jus= t like a=20 pure earth antenna but rather as a combination of this and a ver= y loss=20 dipole. On 137, my power was 100 W at this test.

The ante= nna was=20 built to do local tests but seems to work suitable on 137. So it= is a=20 fixed antenna, my only fixed one. And it is a very quiet locatio= n. This=20 makes it interesting to use it as a RX antenna too!...

73= ,=20 Stefan

-----=20 Original Message -----
Sent:=20 Tuesday, December 14, 2010 2:49 PM
Subject:=20 Re: LF: Earth Electrodes

Hi Chris,

But how do you explain that= i have=20 crossed 49.6 km with a 600m spaced earth electrode antenna= on 8970 Hz?=20 It was rather summer time than winther (regarding QRN)! With= the same=20 antenna, my 137 kHz signal was seen 20 dB above noise near= Paris in=20 DFCW-3!?????

73, Stefan


Am 14.12.2010 15:1= 5, schrieb=20 Chris:=20
Hi Mal,
Yes, that is what I had= concluded years=20 ago. No harm in trying though!
Further to your previous= e-mail to LF,=20 looks to me like beacons are now becoming the norm on 136/= 7kHz band=20 and below. I have no problem with that personally, indeed,= I think=20 it preferable to a QSO taking forever! I woud like to see= full=20 idents though, no matter how slow.
Vy 73,
Chris,=20 G4AYT.
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