Date: Fri, 22 Jan 2010 10:10:29 +0100
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
In-Reply-To: <fc7eccec1001220032n479948e0r952ce47d5420acbd@mail.gmail.co
 m>
References: <9afca2641001210904h7d2b276dv503b55075ce9313@mail.gmail.com>
 <007501ca9acc$e78e29a0$0301a8c0@your91hoehfy9g>
 <fc7eccec1001211127p577825c4m2b4007edd1503dd8@mail.gmail.com>
 <38A51B74B884D74083D7950AD0DD85E82A1AA1@File-Server-HST.hst.e-technik.tu-darmstadt.de>
 <fc7eccec1001220032n479948e0r952ce47d5420acbd@mail.gmail.com>
Mime-Version: 1.0
Message-Id: <20100122091028.4953C31E702@smtps01.kuleuven.be>
Subject: Re: LF: ERP<>EMRP
Content-Type: multipart/alternative;
	boundary="=====================_92078544==.ALT"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


--=====================_92078544==.ALT
Content-Type: text/plain; charset="iso-8859-1"; format=flowed
Content-Transfer-Encoding: quoted-printable

Andy, Stefan,

the theoretical values are:
isotropic antenna: 0dBi / -2.15dBd (directivity =3D 1)
half wave dipole: 2.15dBi / 0dBd (directivity =3D 1.64)
short dipole: 1.76dBi / -0.39dBd (directivity =3D 1.5)
quarter wave vertical monopole: 5.16dBi / 3dBd (directivity 3.28)
short vertical monopole: 4.77dBi / 2.64dBd (directivity 3)
This values assume free space for the dipoles and=20
a perfect (conductive) ground plane for the=20
monopoles. And no losses (greenery, buildings).
For a certain area in north-east England these values are +/- 100dB

For calculating the (theoretical) EIRP one need=20
to take the dBi values or the directivity
For calculating the (theoretical) ERP one need to=20
take the dBd values or divide the directivity by=20
1.64 (there comes Stefan's 1.83 =3D 3/1.64)
For calculating the (theoretical) EMRP the=20
reference is a short monopole, one need to take=20
the dBi-4.77 or dBd-2.62 values or divide the directivity by 3.

So EIRP gives the "best" values, that's why=20
manufacturers of inferior antennas often give dBi=20
values on their prospects but mention just dB ;-)
An easy way to add a good 2dB to the gain.

73, Rik  ON7YD

At 09:32 22/01/2010, you wrote:
>Well, yes it is I suppose if you lump antenna directivity into the equati=
on.
>I^2.R is the actual power radiated.
>Which direction it then goes is a different issue.
>
>Anyway, what is the true directivity figure to use for a monopole ?
>A very short dipole has 1.5 times=20
>directivity.  Therefore a short monopole over=20
>perfect ground ought to have 3 times.  Neither of which is 1.83
>
>Andy
><http://www.g4jnt.com>www.g4jnt.com
>
>This email has been scanned for damaging=20
>side-effects by the health and safety police, is=20
>guaranteed to contain no substances hazardous to=20
>health, but may contribute to dissolving the nether and polar regions
>
>
>2010/1/21 Stefan Sch=E4fer=20
><<mailto:schaefer@hst.tu-darmstadt.de>schaefer@hst.tu-darmstadt.de>
>Hi Andy,
>
>Isn't it, the ERP is I^2*Rrad*1,83, if we assume a vertical antenna?
>
>73, Stefan
>
>________________________________
>
>Von:=20
><mailto:owner-rsgb_lf_group@blacksheep.org>owner-rsgb_lf_group@blacksheep=
.org=20
>im Auftrag von Andy Talbot
>Gesendet: Do 21.01.2010 20:27
>An: <mailto:rsgb_lf_group@blacksheep.org>rsgb_lf_group@blacksheep.org
>Betreff: Re: LF: Re: M0BMU - any chance of some new ERP estimates please?
>
>
>So go on:  argue against the Rrad (an exact=20
>figure derived from basic electromag theory) and=20
>Rloss (easily measurable, called Ohms law) way of getting antenna efficie=
ncy.
>
>Or  ERP =3D   I^2 . Rrad   where I is measurable.
>
>Only uncertainty in any of these techniques is=20
>the effective height of the antenna used to get=20
>Rrad, but absolute worst case, can only ever=20
>lead to 6dB error.  The difference between no top hat and an infinite top=
 hat
>
>Andy
><http://www.g4jnt.com/>www.g4jnt.com <http://www.g4jnt.com/>
>
>

--=====================_92078544==.ALT
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<html>
<body>
Andy, Stefan,<br><br>
the theoretical values are:<br>
isotropic antenna: 0dBi / -2.15dBd (directivity =3D 1)<br>
half wave dipole: 2.15dBi / 0dBd (directivity =3D 1.64)<br>
short dipole: 1.76dBi / -0.39dBd (directivity =3D 1.5)<br>
quarter wave vertical monopole: 5.16dBi / 3dBd (directivity 3.28)<br>
short vertical monopole: 4.77dBi / 2.64dBd (directivity 3)<br>
This values assume free space for the dipoles and a perfect (conductive)
ground plane for the monopoles. And no losses (greenery, buildings).<br>
For a certain area in north-east England these values are +/-
100dB<br><br>
For calculating the (theoretical) EIRP one need to take the dBi values or
the directivity<br>
For calculating the (theoretical) ERP one need to take the dBd values or
divide the directivity by 1.64 (there comes Stefan's 1.83 =3D 3/1.64)<br>
For calculating the (theoretical) EMRP the reference is a short monopole,
one need to take the dBi-4.77 or dBd-2.62 values or divide the
directivity by 3.<br><br>
So EIRP gives the &quot;best&quot; values, that's why manufacturers of
inferior antennas often give dBi values on their prospects but mention
just dB ;-)<br>
An easy way to add a good 2dB to the gain.<br><br>
73, Rik&nbsp; ON7YD<br><br>
At 09:32 22/01/2010, you wrote:<br>
<blockquote type=3Dcite class=3Dcite cite=3D"">Well, yes it is I suppose=
 if you
lump antenna directivity into the equation.&nbsp; <br>
I^2.R is the actual power radiated. <br>
Which direction it then goes is a different issue.<br>
&nbsp;<br>
Anyway, what is the true directivity figure to use for a monopole ?<br>
A very short dipole has 1.5 times directivity.&nbsp; Therefore a short
monopole over perfect ground ought to have 3 times.&nbsp; Neither of
which is 1.83<br><br>
Andy<br>
<a href=3D"http://www.g4jnt.com">www.g4jnt.com</a><br><br>
This email has been scanned for damaging side-effects by the health and
safety police, is guaranteed to contain no substances hazardous to
health, but may contribute to dissolving the nether and polar
regions<br><br>
<br>
2010/1/21 Stefan Sch=E4fer
&lt;<a href=3D"mailto:schaefer@hst.tu-darmstadt.de">
schaefer@hst.tu-darmstadt.de</a>&gt;<br>

<dl>
<dd>Hi Andy,<br><br>

<dd>Isn't it, the ERP is I^2*Rrad*1,83, if we assume a vertical
antenna?<br><br>

<dd>73, Stefan<br><br>

<dd>________________________________<br><br>

<dd>Von:
<a href=3D"mailto:owner-rsgb_lf_group@blacksheep.org">
owner-rsgb_lf_group@blacksheep.org</a> im Auftrag von Andy Talbot<br>

<dd>Gesendet: Do 21.01.2010 20:27<br>

<dd>An:
<a href=3D"mailto:rsgb_lf_group@blacksheep.org">
rsgb_lf_group@blacksheep.org</a><br>

<dd>Betreff: Re: LF: Re: M0BMU - any chance of some new ERP estimates
please?<br><br>
<br>

<dd>So go on:&nbsp; argue against the Rrad (an exact figure derived from
basic electromag theory) and Rloss (easily measurable, called Ohms law)
way of getting antenna efficiency.<br><br>

<dd>Or&nbsp; ERP =3D&nbsp;&nbsp; I^2 . Rrad&nbsp;&nbsp; where I is
measurable.<br><br>

<dd>Only uncertainty in any of these techniques is the effective height
of the antenna used to get Rrad, but absolute worst case, can only ever
lead to 6dB error.&nbsp; The difference between no top hat and an
infinite top hat<br><br>

<dd>Andy<br>

<dd><a href=3D"http://www.g4jnt.com/">www.g4jnt.com</a>
&lt;<a href=3D"http://www.g4jnt.com/" eudora=3D"autourl">
http://www.g4jnt.com/</a>&gt;<br><br>
<br>

</dl></blockquote></body>
</html>

--=====================_92078544==.ALT--