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How does a tracking antenna work? - RF Cafe Forums
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| Mr.Whatever
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Post subject: How does a tracking antenna work?
Posted: Tue Mar 20, 2007 3:45 pm
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| Captain |
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Joined: Fri Apr 07, 2006
6:10 pm
Posts: 18 |
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Good day everyone!
I am curious about the
inner-workings of a tracking antenna. How exactly
does it track a signal and what issues does it have?
I've read somewhere that they may have some polarization
issues and such.
Thanks!
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nubbage |
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Post subject:
Posted: Wed Mar 21, 2007 11:12 am
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| General |
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Joined: Fri Feb 17, 2006
12:07 pm
Posts: 218
Location: London UK
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Hi Mr Whatever. It is me again.
The antenna is
usually configured as an array of a minimum of 4
elements. The signals are fed into a matrix of hybrids
in such a way that there is a sum of the element
patterns for the horizontal plane, and for the vertical
plane, and there is a difference port for each.
The difference port produces a deep null along the
array boresight for each plane. To one side of boresight
the phase is positive, but when the source is to
the other side of antenna boresight the phase reverses,
the sum ports providing the phase reference. Detectors
on the difference ports can be connected to a servo
mechanism that drives the antenna so that it oscillates
very slightly either side of boresight in each plane
ie azimuth and elevation.
I have the hybrid coupler
configuration I could upload if anyone is interested.
Polarization purity is important only to the extent
that if severe cross-polarization occurs, the null
in the difference channel is not so deep. At least
I seem to recall that was the argument when I was
involved in tracking radars.
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Mr.Whatever |
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Post subject:
Posted: Fri Mar 23, 2007 2:55 pm
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| Captain |
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Joined: Fri Apr 07, 2006
6:10 pm
Posts: 18 |
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Thanks again, nubbage! Hopefully, that propagation
stuff has been taken care of already.
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nubbage |
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Post subject:
Posted: Mon Mar 26, 2007 5:19 am
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| General |
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Joined: Fri Feb 17, 2006
12:07 pm
Posts: 218
Location: London UK
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Hi Mr Whatever
My pleasure. Do you need the coupler
configuration up-load?
Ref the OTH propagation
issue: thanks for your help. I sorted out the typos
and other inconsistencies in the article, and derived
a value for Over The Horizon Loss. It differs again
from all the others, which all differ from each
other.
I realize now what the problem is: it
is statistics, not science.
"There are estimates,
rough estimates and statistics".
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Mr.Whatever |
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Post subject:
Posted: Mon Mar 26, 2007 8:52 pm
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| Captain |
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Joined: Fri Apr 07, 2006
6:10 pm
Posts: 18 |
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Hi nubbage,
Yeah, if you can upload it or
send me a quick email.
Thanks!
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Posted 11/12/2012
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