[AMPS] High Voltage at Antenna Ends
Mike Sawyer
kc4slk@csrlink.net
Mon, 11 Sep 2000 20:32:45 -0400
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Remember too, Colin, that it also cuts down on the efficiency.
Mike(y)
W3SLK
----- Original Message -----=20
From: Colin Lamb=20
To: Amps reflector=20
Sent: Monday, September 11, 2000 12:18 PM
Subject: [AMPS] High Voltage at Antenna Ends
One way to prevent high voltage at the ends of an antenna is to reduce =
the Q. The easiest way to do this is to use a lossy wire for the =
antenna. This will also reduce the SWR variations as you change =
frequency. =20
Galvanized Iron electric fence wire is cheap and reduces Q nicely. =
Since losses are high, it reduces noise pick up on receive - especially =
from stations a long distance away.=20
For the ultimate in Q reduction, nichrome works very well. With at =
least a quarter wave of nichrome, the end insulators can be made of =
silver and they will not introduce appreciable losses.
Lossy antennas eliminate the need for antenna tuners and eliminate the =
need to calculate 1/4 waves. They also allow you to tune up on the =
actual antenna without having to bother with the dummy load - a real =
boon to contest operators who like to tune up on frequency. =20
For quiet reception, the ultimate antenna is created by removing the =
center conductor from 1/4 wave coax and replacing it with 1/4 wave of =
nichrome. =20
The cubical quad was invented to eliminate corona effect of high power =
antennas. Beams and dipoles in the Andes had the corona effect and kept =
destroying themselves. Apparently the designer did not know about =
nichrome. Instead, he built a quad to eliminate ends of the antenna. =20
Colin K7FM
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<DIV><FONT face=3D"BellGothic Blk BT">Remember too, Colin, that it also =
cuts down=20
on the efficiency.</FONT></DIV>
<DIV><FONT face=3D"BellGothic Blk BT">Mike(y)<BR>W3SLK</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A href=3D"mailto:k7fm@teleport.com" title=3Dk7fm@teleport.com>Colin =
Lamb</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
href=3D"mailto:amps@contesting.com"=20
title=3Damps@contesting.com>Amps reflector</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Monday, September 11, =
2000 12:18=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [AMPS] High Voltage at =
Antenna=20
Ends</DIV>
<DIV><BR></DIV>
<DIV><FONT face=3DArial size=3D2>One way to prevent high voltage at =
the ends of an=20
antenna is to reduce the Q. The easiest way to do this is to use =
a lossy=20
wire for the antenna. This will also reduce the SWR variations =
as you=20
change frequency. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Galvanized Iron electric fence wire =
is cheap and=20
reduces Q nicely. Since losses are high, it reduces noise pick =
up on=20
receive - especially from stations a long distance away. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>For the ultimate in Q reduction, =
nichrome works=20
very well. With at least a quarter wave of nichrome, the end =
insulators=20
can be made of silver and they will not introduce appreciable=20
losses.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Lossy antennas eliminate the need for =
antenna=20
tuners and eliminate the need to calculate 1/4 waves. They =
also=20
allow you to tune up on the actual antenna without having to bother =
with the=20
dummy load - a real boon to contest operators who like to tune up on=20
frequency. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>For quiet reception, the ultimate =
antenna is=20
created by removing the center conductor from 1/4 wave coax and =
replacing it=20
with 1/4 wave of nichrome. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>The cubical quad was invented to =
eliminate corona=20
effect of high power antennas. Beams and dipoles in the Andes =
had the=20
corona effect and kept destroying themselves. Apparently the =
designer=20
did not know about nichrome. Instead, he built a quad to =
eliminate ends=20
of the antenna. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Colin =20
K7FM</FONT></DIV></BLOCKQUOTE></BODY></HTML>
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