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Transponder antenna - blade vs stub monopole



 
 
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  #21  
Old June 15th 08, 07:39 PM posted to rec.aviation.soaring
COLIN LAMB
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Posts: 94
Default Transponder antenna - blade vs stub monopole

At 1,000 MHz, RG-58 has a loss of about 15 db per 100 feet. So, a 10 foot
run would represent 1.5 db. That is an acceptable loss. It will reduce the
range a bit.

Generally, if the control cables are not resonant and not in the same plane
as the antenna (horixontal controls, vertical antenna), there should be
minimal interference. There are a number of antenna plotting programs arund
that would allow you to plot the potential interference. to determine the
possible interference.

Colin Lamb


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  #22  
Old June 15th 08, 10:26 PM posted to rec.aviation.soaring
Martin Gregorie[_3_]
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Posts: 28
Default Transponder antenna - blade vs stub monopole

On Sun, 15 Jun 2008 11:39:22 -0700, COLIN LAMB wrote:

At 1,000 MHz, RG-58 has a loss of about 15 db per 100 feet. So, a 10 foot
run would represent 1.5 db. That is an acceptable loss. It will reduce the
range a bit.

Generally, if the control cables are not resonant and not in the same plane
as the antenna (horixontal controls, vertical antenna), there should be
minimal interference. There are a number of antenna plotting programs arund
that would allow you to plot the potential interference. to determine the
possible interference.

That's exactly what I wanted to know. Many thanks.

--
[email protected] | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot


  #23  
Old July 2nd 08, 10:39 PM posted to rec.aviation.soaring
Eric Greenwell
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Posts: 1,096
Default Transponder antenna - blade vs stub monopole

Alan wrote:
In article brianDG303 writes:
Is there a downside to mounting on a ground plane inside the fuselage
of a non-carbon glass glider?


Since the ground plane should extend at least 23 inches in each
direction around the antenna, it is probably hard to get that inside
the glider.


That sounds like a dimension for the aircraft communication radio,
working in the 120-130 mhz range. The transponder uses 1090 mhz, about
10 times higher. That indicates a 2.3" radius ground plane would be
adequate, or the 6" diameter Marc points out as commonly used.

--
Eric Greenwell - Washington State, USA
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