Return-Path: Received: from rly-db08.mx.aol.com (rly-db08.mail.aol.com [172.19.130.83]) by air-db10.mail.aol.com (v125.7) with ESMTP id MAILINDB104-ae24acd15b32df; Wed, 07 Oct 2009 18:27:19 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-db08.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDB088-ae24acd15b32df; Wed, 07 Oct 2009 18:27:00 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Mvexc-0001Sv-RT for rs_out_1@blacksheep.org; Wed, 07 Oct 2009 23:26:16 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Mvexb-0001Sm-UN for rsgb_lf_group@blacksheep.org; Wed, 07 Oct 2009 23:26:15 +0100 Received: from imr-da03.mx.aol.com ([205.188.105.145]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1MvexQ-0007pL-1d for rsgb_lf_group@blacksheep.org; Wed, 07 Oct 2009 23:26:06 +0100 Received: from imo-da04.mx.aol.com (imo-da04.mx.aol.com [205.188.169.202]) by imr-da03.mx.aol.com (8.14.1/8.14.1) with ESMTP id n97MPt8w021342 for ; Wed, 7 Oct 2009 18:25:55 -0400 Received: from MarkusVester@aol.com by imo-da04.mx.aol.com (mail_out_v42.5.) id l.c49.46d53770 (45077) for ; Wed, 7 Oct 2009 18:25:53 -0400 (EDT) Received: from smtprly-dd03.mx.aol.com (smtprly-dd03.mx.aol.com [205.188.84.131]) by cia-mc03.mx.aol.com (v125.7) with ESMTP id MAILCIAMC031-d40c4acd1566273; Wed, 07 Oct 2009 18:25:53 -0400 Received: from webmail-m037 (webmail-m037.sim.aol.com [64.12.101.220]) by smtprly-dd03.mx.aol.com (v125.7) with ESMTP id MAILSMTPRLYDD038-d40c4acd1566273; Wed, 07 Oct 2009 18:25:42 -0400 References: <57a24ca70910070818o2e4adde4k1c8daa318eb2eb30@mail.gmail.com> <006001ca4763$a69a1290$0301a8c0@mal769a60aa920> <002601ca4766$1ff29bb0$6c01a8c0@DELL4> <4ACCD7FA.5080501@ukonline.co.uk> <4ACCB110.8A4E.00FD.0@globalstar.com> To: rsgb_lf_group@blacksheep.org Date: Wed, 07 Oct 2009 18:25:42 -0400 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: Markus Vester X-MB-Message-Type: User X-Mailer: Webmail 28200-STANDARD Received: from 188.46.66.168 by webmail-m037.sysops.aol.com (64.12.101.220) with HTTP (WebMailUI); Wed, 07 Oct 2009 18:25:42 -0400 Message-Id: <8CC15B43D9810AE-39D4-4524@webmail-m037.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: MarkusVester@aol.com X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,UNPARSEABLE_RELAY=0.001 Subject: Re: LF: Re Propagation report Content-Type: multipart/alternative; boundary="--------MB_8CC15B43DA3F793_39D4_8DAF_webmail-m037.sysops.aol.com" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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-IP: 193.82.116.20 ----------MB_8CC15B43DA3F793_39D4_8DAF_webmail-m037.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Dear Jim, David, I have been successfully using a variant of the second method, which works= by comparing received voltages of a strong distant transmitter (eg. DCF39= ) from the transmit antenna under test, versus a small nonresonant loop of= known geometrical area. The induced loop voltage is =C2=A0Uloop =3D H * omega * aloop =3D E * aloop * 2 pi / lambda. The effective height of the TX antenna then is =C2=A0htx =3D Utx / E =3D Utx / Uloop * aloop * 2 pi / lambda, and the radiation resistance =C2=A0Rrad =3D 1579 ohm * (htx / lambda)**2 One advantage is that electrical near field shielding effects (eg. by tree= s) are actually included in the voltage ratio, because the reference measu= rement is based on magnetic field and thus hardly affected by moderately= conducting objects in the vicinity. As the effective height is only weakl= y frequency dependent, the measurement can be done at a different frequenc= y, depending on signal availibility.=20 Absolute receiver calibration is not required for the voltage ratio, but= you may have to apply a correction for loading of the tx antenna source= impedance by the receiver impedance: =C2=A0Utx =3D Utx_loaded * (Rant + Rrec) / Rrec I also found that I had to detune or disconnect the big antenna=C2=A0durin= g the loop measurement. Best regards, Markus (DF6NM) -----Urspr=C3=BCngliche Mitteilung-----=20 Von: James Moritz An: rsgb_lf_group@blacksheep.org Verschickt: Mi., 7. Okt. 2009, 21:57 Them a: Re: LF: Re Propagation report Dear David, LF Group,=C2=A0 =C2=A0 There are basically two ways of determining ERP, briefly:=C2=A0 =C2=A0 Method 1 is to calculate the radiation resistance (Rrad) of your antenna,= which can be done using various text-book formulae, or using antenna simu= lation software like EZNEC or similar. Then you measure the RF current flo= wing in the antenna (Iant). The ERP is then Iant^2 x Rrad x 1.8 (1.8 is th= e directivity of electrically small vertical or loop antennas, which in pr= actice is what all amateur 136kHz antennas are).=C2=A0 =C2=A0 Method 2 is to measure the field strength some km from the antenna. The ER= P is then (E x d)^2 /49, where E is the field strength, d distance in metr= es. This requires a calibrated antenna and measuring receiver, so is more= complicated to do.=C2=A0 =C2=A0 Method 1 is simpler to do, but yields ERP results that tend to be lower th= an those obtained by method 2. This is thought to be due to various combin= ed environmental effects on the antenna, which are not accounted for in th= e simple calculation. So to get a more accurate and definitive figure, you= need to do method 2, but as far as compliance with licence conditions is= concerned, method 1 is a conservative way of checking.=C2=A0 =C2=A0 Good luck in your efforts!=C2=A0 =C2=A0 Cheers, Jim Moritz=C2=A0 73 de M0BMU=C2=A0 =C2=A0 ----- Original Message ----- but From: "David Weinreich" =C2=A0 To: =C2=A0 Sent: Wednesday, October 07, 2009 8:17 PM=C2=A0 Subject : Re: LF: Re Propagation report=C2=A0 =C2=A0 Peter,=C2=A0 =C2=A0 As an interested observer from the other side of the pond, how do you dete= rmine that you are close to the ERP limit?? I'd be interested in knowing= as I am trying to do some pro-bono work for the ARRL on getting use of 13= 7 kHz here in the USA.=C2=A0 =C2=A0 Tnx & 73,=C2=A0 =C2=A0 David Weinreich=C2=A0 WA2VUJ/3=C2=A0 =C2=A0 =C2=A0 ----------MB_8CC15B43DA3F793_39D4_8DAF_webmail-m037.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Dear Jim, David,
 
I have been successfully using a variant of the second method, which= works by comparing received voltages of a strong distant transmitter (eg.= DCF39) from the transmit antenna under test, versus a small nonresonant= loop of known geometrical area. The induced loop voltage is
 
 Uloop =3D H * omega * aloop =3D E * aloop * 2 pi / lambda.
 
The effective height of the TX antenna then is
 
 htx =3D Utx / E =3D Utx / Uloop * aloop * 2 pi / lambda,
 
and the radiation resistance
 
 Rrad =3D 1579 ohm * (htx / lambda)**2
 
One advantage is that electrical near field shielding effects (eg. by= trees) are actually included in the voltage ratio, because the reference= measurement is based on magnetic field and thus hardly affected by modera= tely conducting objects in the vicinity. As the effective height is only= weakly frequency dependent, the measurement can be done at a different fr= equency, depending on signal availibility.
 
Absolute receiver calibration is not required for the voltage ratio,= but you may have to apply a correction for loading of the tx antenna sour= ce impedance by the receiver impedance:
 
 Utx =3D Utx_loaded * (Rant + Rrec) / Rrec
 
I also found that I had to detune or disconnect the big antenna = during the loop measurement.
 
Best regards,
Markus (DF6NM)


-----Urspr=C3=BCngliche Mitteilung-----
Von: James Moritz <james.moritz@btopenworld.com>
An: rsgb_lf_group@blacksheep.org
Verschickt: Mi., 7. Okt. 2009, 21:57
Thema: Re: LF: Re Propagation report

Dear David, LF Group, 
 
There are basically two ways of determining ERP, briefly: 
 
Method 1 is to calculate the radiation resistance (Rrad) of your antenna,= which can be done using various text-book formulae, or using antenna simu= lation software like EZNEC or similar. Then you measure the RF current flo= wing in the antenna (Iant). The ERP is then Iant^2 x Rrad x 1.8 (1.8 is th= e directivity of electrically small vertical or loop antennas, which in pr= actice is what all amateur 136kHz antennas are). 
 
Method 2 is to measure the field strength some km from the antenna. The ER= P is then (E x d)^2 /49, where E is the field strength, d distance in metr= es. This requires a calibrated antenna and measuring receiver, so is more= complicated to do. 
 
Method 1 is simpler to do, but yields ERP results that tend to be lower th= an those obtained by method 2. This is thought to be due to=20 various combined environmental effects on the antenna, which are not accou= nted for in the simple calculation. So to get a more accurate and definiti= ve figure, you need to do method 2, but as far as compliance with licence= conditions is concerned, method 1 is a conservative way of checking. = ;
 
Good luck in your efforts! 
 
Cheers, Jim Moritz 
73 de M0BMU 
 
----- Original Message ----- but From: "David Weinreich" <David.Weinreich@globalstar.com>= ; 
To: <rsgb_lf_group@blac= ksheep.org> 
Sent: Wednesday, October 07, 2009 8:17 PM 
Subject: Re: LF: Re Propagation report 
 
Peter, 
 
As an interested observer from the other side of the pond, how do you dete= rmine that you are close to the ERP limit?? I'd be interested in knowing= as I am trying to do some pro-bono work for the ARRL on getting use of 13= 7 kHz here in the USA. 
 
Tnx & 73, 
 
David Weinreich 
WA2VUJ/3 
 
 
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