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From: Markus Vester <markusvester@aol.com>
Message-Id: <8D07CEDAFCE2EF1-16C4-7AA@webmail-m212.sysops.aol.com>
Date: Wed, 11 Sep 2013 06:06:15 -0400 (EDT)
Subject: Re: LF: Radio signals
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Edgar,
=C2=A0
straightforward linear addition of voltages. If both transmitters had same =
power and phase you will get + 6 dB on the receiver.
=C2=A0
If you had two equally (in)efficient LF antennas on the same premises (ie. =
within a wavelength) and=C2=A0drove both=C2=A0equally,=C2=A0you'd need doub=
le TX power in total but achieve four times ERP.=C2=A0This is equivalent to=
 a larger antenna with double efficiency.=20
=C2=A0
The trick won't work that way at HF or VHF, where antennas are alraedy near=
ly 100% efficient, and mutual=C2=A0resistance will increase the required in=
put power for one antenna when the other is activated.=C2=A0Then=C2=A0induc=
ing directivity is the only way to increase gain.

=C2=A0
Best 73,
Markus (DF6NM)

=C2=A0
=C2=A0
-----Urspr=C3=BCngliche Mitteilung-----=20
Von: edgar &lt;edgarjtwining@virginbroadband.com.au&gt;
An: 600m &lt;600m@yahoogroups.com&gt;; rsgb_lf_group &lt;rsgb_lf_group@blac=
ksheep.org&gt;
Verschickt: Mi, 11 Sept 2013 7:05 am
Betreff: LF: Radio signals


Hi Group,=20
 =20
 What is the mechanism for the way radio signals combine in the air?=20
 =20
 For example=20
 =20
 1.There are two transmitters each sending out the same fixed frequency =20
 sine wave signal.=20
 =20
 2. There are no other signals in space, and no background noise.=20
 =20
 3. There are no propagation factors modifying the signals.=20
 =20
 e.g. buildings, ionosphere layers.=20
 =20
 4. Both transmitters are the same distance from the receiver.=20
 =20
 5. Both signals have the same polarisation.=20
 =20
 How have the signals combined when they reach a receiving antenna at a =20
 reasonable distance from both transmitters?=20
 =20
 It the process addition, multiplication or some other process?=20
 =20
 Regards, Edgar=20
 Moonah, Tasmania.=20
 =20
 =20
=20


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<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><FONT colo=
r=3Dblack face=3Darial></FONT><SPAN style=3D"DISPLAY: inline-block" content=
Editable=3Dfalse></SPAN><FONT color=3Dblack face=3Darial>Edgar,</FONT></div=
>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><FONT colo=
r=3Dblack face=3Darial></FONT>&nbsp;</div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><FONT colo=
r=3Dblack face=3Darial>straightforward linear addition of voltages. </FONT>=
If both transmitters had same power and phase you will get + 6 dB on the re=
ceiver.</div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">&nbsp;</di=
v>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">If you had=
 two equally (in)efficient LF antennas <SPAN style=3D"DISPLAY: inline-block=
"></SPAN>on the same premises (ie. within a wavelength) and&nbsp;drove both=
&nbsp;equally,&nbsp;you'd need double TX power in total but achieve four ti=
mes ERP.&nbsp;This is equivalent to a larger antenna with double efficiency=
. </div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">&nbsp;</di=
v>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">The trick =
won't work that way at HF or VHF, where antennas are alraedy nearly 100% ef=
ficient, and mutual&nbsp;resistance will increase the required input power =
for one antenna when the other is activated.&nbsp;Then&nbsp;inducing direct=
ivity is the only way to increase gain.</div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><br>
&nbsp;</div>


<div>Best 73,</div>


<div>Markus (DF6NM)<br>
</div>


<div>&nbsp;</div>


<div>&nbsp;</div>


<div>-----Urspr=C3=BCngliche Mitteilung----- <br>
Von: edgar &lt;<A href=3D"mailto:edgarjtwining@virginbroadband.com.au">edga=
rjtwining@virginbroadband.com.au</A>&gt;<br>
An: 600m &lt;<A href=3D"mailto:600m@yahoogroups.com">600m@yahoogroups.com</=
A>&gt;; rsgb_lf_group &lt;<A href=3D"mailto:rsgb_lf_group@blacksheep.org">r=
sgb_lf_group@blacksheep.org</A>&gt;<br>
Verschickt: Mi, 11 Sept 2013 7:05 am<br>
Betreff: LF: Radio signals<br>
<br>
<br>
</div>


<div style=3D"BACKGROUND-COLOR: #fff; MARGIN: 0px; FONT-FAMILY: Tahoma, Ver=
dana, Arial, Sans-Serif; COLOR: #000; FONT-SIZE: 12px" id=3Daolmail_AOLMsgP=
art_0_05d390d3-29a9-4e7e-a547-ae2919e77412><br>
<br>
<PRE style=3D"FONT-SIZE: 9pt"><TT>Hi Group, <br>
  <br>
 What is the mechanism for the way radio signals combine in the air? <br>
  <br>
 For example <br>
  <br>
 1.There are two transmitters each sending out the same fixed frequency  <b=
r>
 sine wave signal. <br>
  <br>
 2. There are no other signals in space, and no background noise. <br>
  <br>
 3. There are no propagation factors modifying the signals. <br>
  <br>
 e.g. buildings, ionosphere layers. <br>
  <br>
 4. Both transmitters are the same distance from the receiver. <br>
  <br>
 5. Both signals have the same polarisation. <br>
  <br>
 How have the signals combined when they reach a receiving antenna at a  <b=
r>
 reasonable distance from both transmitters? <br>
  <br>
 It the process addition, multiplication or some other process? <br>
  <br>
 Regards, Edgar <br>
 Moonah, Tasmania. <br>
  <br>
  </TT><br>
 </PRE></div>

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