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Antenna placement - RF Cafe Forums
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| Mr.Whatever
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Post subject: Antenna placement
Posted: Fri Apr 07, 2006 6:13 pm
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| Captain |
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Joined: Fri Apr 07, 2006
6:10 pm
Posts: 18 |
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Hello,
Does antenna placement
significantly
affect the radiation pattern of an antenna?
For example, I have a dipole connected to a
metallic box. Will the dipole pattern change? Or
say I have one of those TV antennas, if I place
it on a different section of the roof or a different
part of the house, will that affect the radiation
pattern?
Thanks!
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fred47 |
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Post subject: Antenna positioning
Posted: Fri Apr 07, 2006 8:36 pm
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| General |
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Joined: Wed Feb 22, 2006
3:51 pm
Posts: 104 |
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In a word, yes.
Yes, any nearby conductor
will affect your radiation pattern. That's why AM
broadcasting stations put their antennas over damp
ground - it acts like a reflector does for light.
Near enough, and it also affects the impedance
the antenna presents to the transmission line and
transmitter.
Good Luck!
Fred
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Mr.Whatever |
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Post subject:
Posted: Sat Apr 08, 2006 10:12 am
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| Captain |
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Joined: Fri Apr 07, 2006
6:10 pm
Posts: 18 |
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Thanks! I got into this discussion because a classmate
wanted to have a transmitter installed in his car.
He said he was going to get this antenna that showed
an omnidirectional pattern at his transmitting frequency.
I told him that he should not go with the given
pattern because the car's body will change the actual
pattern. He said that he does not think that the
car frame's frequency response is not the same as
his transmitting frequency so he it should not affect
the pattern.
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fred47 |
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Post subject: Antenna pattern
Posted: Sat Apr 08, 2006 4:29 pm
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| General |
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Joined: Wed Feb 22, 2006
3:51 pm
Posts: 104 |
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Hi again!
The effect of mounting an omnidirectional
antenna on a vehicle depends on the type of antenna,
and where you mount it. A vertical dipole, in the
center of the roof,
will
be omnidirectional. But most dipoles for lower frequencies
are mounted on the fenders or the bumpers, and as
a result will have a preferred direction. It's difficult
to quantify without a lot of details and an analysis
program. Still, bumper mounts are common among the
amateur radio HF users.
Good luck,
Fred
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Posted 11/12/2012
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