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<DIV><!-- Converted from text/plain format --><FONT face=Verdana><STRONG><FONT
size=2><EM> </EM></FONT><FONT
face="Verdana, Arial, Helvetica, sans-serif">LOW NOISE ANTENNA USING THE
UNIVERSAL MAGNETIC BALUN* AND THE ANTENNA FEEDER ISOLATOR
</FONT></STRONG></FONT></DIV>
<DIV><STRONG><FONT face=Verdana></FONT></STRONG> </DIV>
<DIV>
<P align=left><FONT face=Verdana>Longwire Antenna:<FONT size=1><FONT size=3>
<U>The Longwire and the UMB should be positioned far away from sources of
interference such as fluorescent lights, TVs, computers and electrical
wiring</U>. </FONT></FONT></FONT></P>
<P align=left><FONT face=Verdana><FONT size=1><FONT size=3>In most cases
satisfactory results can be obtained by <U>mounting the antenna 6-10m above
ground level</U> and at least <U>6m from any buildings</U>. <U>The antenna's
length should be a minimum of 12m</U>. The UMB should be placed near the ground
at the rear of the garden. Using a sloping or "Inverted L" antenna will ensure
that the connection to the earth rod will be as short as possible.</FONT>
</FONT></FONT></P></DIV>
<DIV><FONT face=Verdana></FONT> </DIV>
<DIV><FONT face=Verdana></FONT><FONT face=Verdana></FONT><FONT
face=Verdana></FONT><BR></DIV>
<P><FONT face="Verdana, Arial, Helvetica, sans-serif"></FONT></P><B><FONT
face=Helvetica,Arial size=4>
<P></P>
<P align=center></FONT><FONT face=Helvetica,Arial><FONT
face="Verdana, Arial, Helvetica, sans-serif" size=2>THE WRONG WAY TO INSTALL A
LONGWIRE ANTENNA/BALUN:</FONT></P></FONT></B>
<P align=center><FONT face="Verdana, Arial, Helvetica, sans-serif" size=2><IMG
height=165 src="http://www.wellbrook.uk.com/images/antwrong.gif"
width=367></FONT></P>
<P align=center><FONT face=Verdana></FONT> </P>
<P align=center><FONT face="Verdana, Arial, Helvetica, sans-serif" size=2><B>THE
CORRECT WAY TO INSTALL A LONGWIRE ANTENNA/BALUN:</B></FONT></P>
<P></P>
<P align=center><FONT face="Verdana, Arial, Helvetica, sans-serif" size=2><IMG
style="WIDTH: 390px; HEIGHT: 142px" height=121
src="http://www.wellbrook.uk.com/images/antright.gif" width=392></FONT></P>
<P align=center><FONT face=Verdana><FONT size=1></FONT></FONT> </P>
<P><FONT face="Verdana, Arial, Helvetica, sans-serif">The Isolator would
normally be placed near to the receiver with a short connection to the earth
rod. </FONT></P>
<P></P>
<P><FONT face="Verdana, Arial, Helvetica, sans-serif">The above installation
will ensure that the antenna is outside the local noise zone which extends up to
5m around the house. Also the noise pickup is lower with the feeder close to the
ground. </FONT></P>
<P><FONT face="Verdana, Arial, Helvetica, sans-serif">The earth return path for
the antenna is a separate earth rod and not the feeder/noisy mains earth as with
most other "Baluns". This can reduce noise by up to 20dB compared to other
"Baluns". </FONT></P>
<P></P>
<P><FONT face="Verdana, Arial, Helvetica, sans-serif">Using the Isolator will
ensure that mains borne noise cannot enter the feeder and couple noise to the
antenna either directly or by the feeder radiation. The Isolator can reduce
noise at low frequencies by up to 40dB. Without an Isolator the feeder is
connected to the receiver/mains earth and is effectively an extension of the
house mains wiring as far as noise is concerned. Connecting the receiver
directly to earth does not generally lower the noise because it is very
difficult to achieve a low impedance earth.</FONT></P>
<DIV><FONT face=Verdana></FONT> </DIV>
<DIV><FONT face=Verdana><STRONG>Fonte</STRONG>: <FONT size=2><EM><FONT
size=3>Wellbrook Communications.</FONT></EM></FONT></FONT></DIV>
<DIV><EM><FONT face=Verdana></FONT></EM> </DIV>
<DIV><FONT face=Verdana></FONT><FONT face=Verdana></FONT> </DIV>
<DIV><FONT face=Verdana><STRONG>BALUN* -</STRONG> tecnicamente nas
antenas de fio comprido aleatório (vulgarmente conhecidas
por "random Longwire" ou somente "Longwire") a denominação
correcta é <STRONG>UNUM </STRONG>( antena "unbalanced" / cabo coaxial
"unbalanced") e não <STRONG>Balun </STRONG>( antena "balanced" / cabo coaxial
"unbalanced") como no caso dos dipolos. Especificamente e neste
caso pode-se prescindir do "Line Isolator AFI 5030" que é
projectado para recepção, ou utilizar um para transmissão, por exemplo os
conhecidos T4 e T5 Line Isolators da Radio Work ( <A
href="http://www.radioworks.com/nliinfo.html">http://www.radioworks.com/nliinfo.html</A> ). </FONT></DIV>
<DIV><FONT face=Verdana></FONT> </DIV>
<DIV><FONT face=Verdana></FONT> </DIV>
<P><FONT face=Verdana>João Costa, CT1FBF</FONT><BR></P></BODY></HTML>