Return-Path: X-Spam-DCC: paranoid 1170; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_MESSAGE,SPF_PASS autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u398YiSc000845 for ; Sat, 9 Apr 2016 10:34:44 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aoo9x-0004Ey-SJ for rs_out_1@blacksheep.org; Sat, 09 Apr 2016 09:22:25 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aoo9x-0004Ep-4V for rsgb_lf_group@blacksheep.org; Sat, 09 Apr 2016 09:22:25 +0100 Received: from nm32.bullet.mail.ir2.yahoo.com ([212.82.96.57]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.87) (envelope-from ) id 1aoo9r-0004c7-W3 for rsgb_lf_group@blacksheep.org; Sat, 09 Apr 2016 09:22:24 +0100 X-DKIM-Result: Domain=yahoo.co.uk Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.co.uk; s=s2048; t=1460190138; bh=LrvN5haAYBKomjyuymybkb4lsHzdckne8gIgyPKEGs4=; h=Date:From:Reply-To:To:In-Reply-To:References:Subject:From:Subject; b=rwyNrUv3ajD7btHC3g2HEelo6RtiWy183EmnwkSqNttVkubNsWvChtD5tQbnyQ3J7Aq4sN/ouZRK98SL0HoZLY3MxhSYqqVvtj1/AahdZBWwmdECQpjhQMtXhV0wnln9oIdKgKDhMpP9NDoxA7IR/dnN9I/F1bdEsUC7LfLbqwC2QUyEMP4SVUhAr5+R5zM8b08CZ5O0G9TmlCtU1YPGGNMM/tkHS+2zUhPObBsyuVjZHVs99bEyGM1EGmPyF6oIxnpuf2dOp1lrnm+lDm6X+ZXSf2ahBrLJNcPcfWIM7lFPx60YWObNkRlofGAbbBk2Ts/AkqWj3hZGyA+UOPkPeA== Received: from [212.82.98.62] by nm32.bullet.mail.ir2.yahoo.com with NNFMP; 09 Apr 2016 08:22:18 -0000 Received: from [212.82.98.65] by tm15.bullet.mail.ir2.yahoo.com with NNFMP; 09 Apr 2016 08:22:18 -0000 Received: from [127.0.0.1] by omp1002.mail.ir2.yahoo.com with NNFMP; 09 Apr 2016 08:22:18 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 751961.12683.bm@omp1002.mail.ir2.yahoo.com X-YMail-OSG: k5VVV5IVM1kcxgjNxgT5QXUbGNthCrytMdN3XWzcev56M6NOjyMVjrADss8xMZf KjTSHO3ew61C4oBA0cas6F9aM83YsvdssG5Dj40W5yJ3.7nEWzOjR3L.sRggU6hgCu1ClZYRY6K9 6LlYvAUD4M6vH8PNpMzmv1hGSJxIMWSxmcpOnjIXn2GOdZXGvhecrcpQlvs_vzriqciP8hc3Ng8O 5xrDCscm41wUD_HjBXMv3JQpxOZNe8d2tUcmaHmuhYtlergt9v9uQIKwfBtH3_YCrTd5XTwwGMps DM2ceMPPiX_skRoPFUTcNpVYWuF798NWT_2k.o_C9CY99BOjkdI.MU8JxmohsHZk_TbM1NQ2vQbN 2JuVe.1.wY5EzX.1Dwn.uxF4oeyyyw8p4bJHwXXTc2eUiGfm4ywFxEk2ouGGVQ6Tw64FJSs2ID1M I.mbQTMRI6Cqt248vLKXGe3sd3MGgE65_nKuDLrkzveIxbl5ckkNGIt94i6FNHiG5ue4kmAA1cUy uY6Ou Received: by 217.12.9.11; Sat, 09 Apr 2016 08:22:17 +0000 Date: Sat, 9 Apr 2016 08:20:27 +0000 (UTC) From: Chris Osborn To: "rsgb_lf_group@blacksheep.org" Message-ID: <1342217774.3243243.1460190027604.JavaMail.yahoo@mail.yahoo.com> In-Reply-To: <7E7DFBB4D102A04DB5ADC88D66628A4A444EBCA7@ICTS-S-MBX1.luna.kuleuven.be> References: <7E7DFBB4D102A04DB5ADC88D66628A4A444EBCA7@ICTS-S-MBX1.luna.kuleuven.be> MIME-Version: 1.0 X-Scan-Signature: 10dccfa1b1e78c2ac07debda8ed18382 Subject: Re: LF: Re: RE: Field Strength Measurements Content-Type: multipart/alternative; boundary="----=_Part_3243242_762761116.1460190027579" 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.11 Status: O X-Status: X-Keywords: X-UID: 7618 ------=_Part_3243242_762761116.1460190027579 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Dear Rik, Many thanks again for the most useful explanation. Some of my past career was spent in an electrical calibration lab. so I can= not get used to the scatter of readings I get with field strength measureme= nts - HI !My calculated value of 0.38 watts ERP was obviously an average of= several readings and theyranged from about 0.25 - 0.5W Your deduction of my aerial current is interesting.My system comrises the T= X, a step down (voltage) transformer, variometer and aerial.The whole syste= m is tuned by means of a 'scopematch' unit and with 56W output the aerial c= urrent, allowing for the step up current transformation is 1.8A My next step (once it stops raining) will be to take some measurements on h= igher ground as suggested. Ian G4GIR (Bedford) and I have been doing some comparison tests on MF.Using= the G3YXM grabber we transmit simultaneously using the same RF power and t= hen compare signals on the grabber's graphic display.Results for the two of= us are similar and with outputs of 56W we indicate at the -60 dB level. Once we get an accurate measurement of our EIRP we could use that grabber a= s a calibrated monitor. 73Chris G3XIZ =20 On Friday, 8 April 2016, 11:30, Rik Strobbe wrote: =20 #yiv7096683814 P {MARGIN-TOP:0px;MARGIN-BOTTOM:0px;}Hello=C2=A0Chris,=C2= =A0a=C2=A0lazy-L of=C2=A09m=C2=A0by=C2=A040m=C2=A0should have a=C2=A0radiat= ion=C2=A0resistance (Rrad) of +/- 0.25 Ohm.If=C2=A0you=C2=A0know the antenn= a=C2=A0current (I)=C2=A0you=C2=A0can=C2=A0calculated the=C2=A0EIRP =3D G*I^= 2*Rrad=C2=A0where G =3D the antenna=C2=A0gain (referred to=C2=A0an=C2=A0iso= tropic antenna).The=C2=A0theoretical=C2=A0gain of a short=C2=A0vertical=C2= =A0monopole is 3 (4.77dBi),=C2=A0but=C2=A0this=C2=A0assumes a perfect=C2=A0= ground and=C2=A0no obstructions. A non perfect=C2=A0ground=C2=A0will affect= the antenna=C2=A0pattern and gain.Whereas=C2=A0the max.=C2=A0takeoff=C2=A0= angle over perfect=C2=A0ground is 0=C2=B0=C2=A0it=C2=A0will=C2=A0rise over = non perfect ground. In=C2=A0addition the=C2=A0gain=C2=A0will=C2=A0slightly = drop.I=C2=A0simulated=C2=A0your antenna=C2=A0using Mmanagal:Over perfect=C2= =A0ground the max.=C2=A0takeoff=C2=A0angle is 0=C2=B0 and the antenna=C2=A0= gain is 4.7dBi.With=C2=A0a "real ground" of 20mS/m and=C2=A0Er=3D 5 the max= .=C2=A0takeoff=C2=A0angle=C2=A0rises=C2=A017=C2=B0 and the antenna=C2=A0gai= n drops to=C2=A04.2dBi (at 17=C2=B0). At a=C2=A0low=C2=A0angle of 1=C2=B0 t= he=C2=A0gain has=C2=A0dropped to -4.3dBi,=C2=A0thus=C2=A08.5dB=C2=A0below t= he max. gain.The=C2=A0fact=C2=A0that maximum=C2=A0gain is=C2=A0not at 0=C2= =B0=C2=A0takeoff=C2=A0makes is=C2=A0difficult to=C2=A0measure E(I)RP at=C2= =A0ground level (cfr.=C2=A0Alans=C2=A0suggestion to go=C2=A0for=C2=A0higher= grounds,=C2=A0if possible).=C2=A0Just out of=C2=A0curiosity a=C2=A0predict= ion of the antenna=C2=A0current=C2=A0based=C2=A0on the=C2=A0numbers above:= =C2=A0with=C2=A0an=C2=A0ERP of=C2=A00.38W (=3D=C2=A0EIRP of 0.62W) and a=C2= =A0gain of=C2=A04.2dBi the antenna=C2=A0current=C2=A0should=C2=A0be close t= o 1A,=C2=A0assuming a=C2=A0takeoff=C2=A0angle of 0=C2=B0.=C2=A0Now=C2=A0tak= ing=C2=A0into account a=C2=A08.5dB low reading (due to the=C2=A0higher=C2= =A0takeoff angle) the=C2=A0real antenna=C2=A0current=C2=A0should=C2=A0be 2.= 6 A.=C2=A073,=C2=A0Rik=C2=A0=C2=A0ON7YD - OR7T=C2=A0Van: owner-rsgb_lf_grou= p@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Chris Osborn [= g3xiz@yahoo.co.uk] Verzonden: vrijdag 8 april 2016 11:36 Aan: rsgb_lf_group@blacksheep.org Onderwerp: Re: LF: Re: RE: Field Strength Measurements Many thanks for the rapid replies gentlemen; they are very much appreciated= . Rik, thanks for the explanation of the two formulae and I've inserted that = ERP formula into my spreadsheet now - excellent ! Alan, I take measurements in open fields to the south of Biggleswade and at= about 1 - 1.5 km distance from the transmitter.Noted about the advantages = of higher ground measurement but we're fairly flat around here - HI !I'll l= ook at the O/S map and see what I can do. Transmitting 56 watts my ERP was calculated as being 0.38 watts which just = seemed rather low.My aerial is a 40 m long inverted 'L' at 9m mean height w= ith a reasonable ground system. Making measurments of G4GIR's transmissions with his 260 watts at 16 km ret= urned a value of 0.88 watts ERP 73Chris G3XIZ On Friday, 8 April 2016, 0:24, Alan Melia wrote= : #yiv7096683814 P {MARGIN-TOP:0px;MARGIN-BOTTOM:0px;}Chris two other points1= .=C2=A0 How far from the aerial are you taking the measurement .....you nee= d to be at least 300 to 500 metres away2=C2=A0=C2=A0 Because of ground loss= problems even the best (fully in the clear)=C2=A0amateur short aerials mea= sure around 5 to 6 dB low.(that is a 136kHz observation.) Often a better re= ading is taken say a mile away on slightly elevated ground to the aerial si= te. Jim Moritz did tests in a field adjacent to the Puckeridge Decca mast, = with a 10m high inverted L.=C2=A0AlanG3NYK=C2=A0=C2=A0 ----- Original Message ----- From: Rik Strobbe To: rsgb_lf_group@blacksheep= .org Sent: Thursday, April 07, 2016 11:24 PMSubject: LF: RE: Field Strength= Measurements Hello Chris,=C2=A0(1) will give you the EMRP (Effective Monopole Radiated P= ower)(2) will give you the EIRP (Effective Isotropic Radiated Power)The for= mula P =3D 0.0203252(Ed)^2 will give you the ERP (Effective Radiated Power)= =C2=A073, Rik=C2=A0 ON7YD - OR7T=C2=A0Van:owner-rsgb_lf_group@blacksheep.or= g [owner-rsgb_lf_group@blacksheep.org] namens Chris Osborn [g3xiz@yahoo.co.= uk] Verzonden: donderdag 7 april 2016 23:58 Aan: LF Group Onderwerp: LF: Field Strength Measurements LF,=20 I've recently resurrected my old RF field strength meter as designed by PA0= SE and published in the LF Experimenters' Handbook.I've modifed it to measu= re signals in the MF band and have calibrated it with a home made Helmholtz= coil arrangement. This question may have been raised before but PA0SE gives the formula for d= eriving the transmitter power as P =3D 0.0111 (Ed)^2=C2=A0 . . .=C2=A0=C2=A0 (1) where E is the electrical field strength and d the distance I've read in other places that the power from an isotropic radiator is P =3D (Ed)^2 / 30=20 i.e.=C2=A0 0.0333 (Ed)^2=C2=A0 . . . . (2) My calculated radiated power seems rather low so I'm wondering whether I sh= ould be using formula (2) Any clarification would be most welcome. 73Chris G3XIZ ------=_Part_3243242_762761116.1460190027579 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Dear Rik,

Many thanks again for t= he most useful explanation.

Some of= my past career was spent in an electrical calibration lab. so I cannot get= used to the scatter of readings I get with field strength measurements - H= I !
My calculated va= lue of 0.38 watts ERP was obviously an average of several readings and they=
ranged = from about 0.25 - 0.5W

Your deduction of my aerial current is interesting.
My system comrises = the TX, a step down (voltage) transformer, variometer and aerial.
The whole system = is tuned by means of a 'scopematch' unit and with 56W output the aerial cur= rent, allowing for the step up current transformation is 1.8A

My next step (once it s= tops raining) will be to take some measurements on higher ground as suggest= ed.

=
Ian G4G= IR (Bedford) and I have been doing some comparison tests on MF.
Using the G3YXM gra= bber we transmit simultaneously using the same RF power and then compare si= gnals on the grabber's graphic display.
Results for the two of us are similar and w= ith outputs of 56W we indicate at the -60 dB level.

Once we get an accurate measuremen= t of our EIRP we could use that grabber as a calibrated monitor.

73
Chris G3XIZ



<= br>
On Friday, 8 = April 2016, 11:30, Rik Strobbe <rik.strobbe@fys.kuleuven.be> wrote:


Hello Chris,
 
a lazy-L of = ;9m=  by 40m shou= ld have a radiation resistance (Rrad<= /a>) of +/- 0.25 Ohm.
If you know the antenna current (I) you can ca= lculated the EIRP =3D G*I^2*Rrad where G =3D the antenna gain (referred to an i= sotropic antenna).
The theoretical&= nbsp;gain of a short = vertical monopole is 3 (4.77dBi), but this assumes a perfect ground and=  no obstructions. A non perfect ground will affect the antenna pattern and gain.
Whereas the max.=  takeoff angle over perfect ground is 0=C2=B0 it will rise over non perfect ground. In addition the = ;gain will slightly drop.
I simulated = ;your antenna using Mmanagal= :
Over perfect ground<= /a> the max. takeoff&= nbsp;angle is 0=C2=B0 and = the antenna gain is 4= .7dBi.
With a "real ground" of 20mS/m and Er=3D 5= the max. takeoff&nbs= p;angle rises 17=C2=B0 and the antenna gain= drops to 4.2dBi (at 17=C2=B0). At a low angle of 1=C2=B0 the gain has dropped to -4.3dBi, thus 8.5dB<= /a> below the max. gain.
The fact th= at maximum gain is not at 0=C2=B0 takeoff makes is difficult to measure E(I)RP at ground level (cfr= . Alans sugges= tion to go for higher grounds, if possible).<= /div>
 
Just out of curiosity a prediction of the antenna current<= a href=3D"" rel=3D"nofollow" shape=3D"rect"> based on the numbers above: with an ERP of 0.38W (=3D EIRP= of 0.62W) and a gain of 4.2dBi the antenna current should=  be close to 1A, as= suming a takeoff angle= of 0=C2=B0. Now taking into account a 8.5dB low reading (due to the higher t= akeoff angle) the real antenna current should be 2.6 A.
 
73, Rik  ON7YD - OR7T
 
Van: owner-rsgb_lf_group@blackshe= ep.org [owner-rsgb_lf_group@blacksheep.org] namens Chris Osborn [g3xiz@yaho= o.co.uk]
Verzonden: vrijdag 8 april 2016 11:36
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: Re: RE: Field Strength Measurements

Many thanks f= or the rapid replies gentlemen; they are very much appreciated.

R= ik, thanks for the explanation of the two formulae and I've inserted that E= RP formula into my spreadsheet now - excellent !
<= br clear=3D"none">
A= lan, I take measurements in open fields to the south of Biggleswade and at = about 1 - 1.5 km distance from the transmitter.
N= oted about the advantages of higher ground measurement but we're fairly fla= t around here - HI !
I= 'll look at the O/S map and see what I can do.
<= br clear=3D"none">
T= ransmitting 56 watts my ERP was calculated as being 0.38 watts which just s= eemed rather low.
M= y aerial is a 40 m long inverted 'L' at 9m mean height with a reasonable gr= ound system.
<= br clear=3D"none">
M= aking measurments of G4GIR's transmissions with his 260 watts at 16 km retu= rned a value of 0.88 watts ERP
<= br clear=3D"none">
7= 3
C= hris G3XIZ
<= br clear=3D"none">
<= br clear=3D"none">
=


On Friday, 8 April 2016, 0= :24, Alan Melia <alan.melia@btinternet.com> wrote:


Chris two other points
1.  How far from the aerial are y= ou taking the measurement .....you need to be at least 300 to 500 metres aw= ay
2   Because of ground loss p= roblems even the best (fully in the clear) amateur short aerials measu= re around 5 to 6 dB low.(that is a 136kHz observation.) Often a better read= ing is taken say a mile away on slightly elevated ground to the aerial site. Jim Moritz did tests in a field adjacent to the Pucker= idge Decca mast, with a 10m high inverted L.
 
Alan
G3NYK
 
 
----- Original Message -----
Sent: Thursday, April 07, 2016 11:24= PM
Subject: LF: RE: Field Strength Meas= urements

Hello Chris,
 
(1) will give you the EMRP (Effective Monopole Radiated Power)
(2) will give you the EIRP (Effective Isotropic Radiated Power)
The formula P =3D 0.0203252(Ed)^2 will give you the ERP (Effective Rad= iated Power)
 
73, Rik  ON7YD - OR7T
 
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org]= namens Chris Osborn [g3xiz@yahoo.co.uk]
Verzonden: donderdag 7 april 2016 23:58
Aan: LF Group
Onderwerp: LF: Field Strength Measurements

LF,

I've recently= resurrected my old RF field strength meter as designed by PA0SE and publis= hed in the LF Experimenters' Handbook.
I've modifed = it to measure signals in the MF band and have calibrated it with a home mad= e Helmholtz coil arrangement.

This question= may have been raised before but PA0SE gives the formula for deriving the t= ransmitter power as

P =3D 0.0111 = (Ed)^2  . . .   (1)

where E is th= e electrical field strength and d the distance

I've read in = other places that the power from an isotropic radiator is

P =3D (Ed)^2 = / 30

i.e.  0.= 0333 (Ed)^2  . . . . (2)

My calculated= radiated power seems rather low so I'm wondering whether I should be using= formula (2)

Any clarifica= tion would be most welcome.

73
Chris G3XIZ











------=_Part_3243242_762761116.1460190027579--