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Antenna radiation pattern - RF Cafe Forums

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Mr.Whatever
 Post subject: Antenna radiation pattern
Posted: Mon Aug 14, 2006 1:07 pm 
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Joined: Fri Apr 07, 2006 6:10 pm
Posts: 18
Hello folks,

I was reading this website: http://www.qsl.net/aa3rl/ant2.html. It got me thinking. In general, does the term "above ground" refer to the actual Earth ground or does it refer to an antenna's ground plane (not necessarily Earth ground)?

I was looking at the radiation patterns, and I got curious what would happen if we actually have a dipole antenna that is attached to a bird (for example). Will the radiation pattern change as the bird's flying height changes? Or will the flying antenna maintain the same radiation pattern as a "normal" antenna that is mounted on a mast at the same height?


 
   
 
languer
 Post subject:
Posted: Mon Aug 14, 2006 3:57 pm 
 
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Location: Earth
Cool question,

Can't say I've tried it (antenna-on-a-bird that is), but as the distance from the bird (thus the antenna) to the ground changes so will the radiation (for the antenna example suggested in the link). Response of course changes with antenna types. And if somehow you could fit the bird with a counterpoise, then this would act as the image plane and the effects of earth ground proximity would be lessened.

Do you have some application in mind?


 
   
 
Mr.Whatever
 Post subject:
Posted: Tue Aug 15, 2006 9:49 am 
 
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Joined: Fri Apr 07, 2006 6:10 pm
Posts: 18
:-)

There are several application that can benefit from a "levitated" antenna / transmitter setup. Now, if we change the bird to a balloon, then many applications come to mind. I guess the main thing that I'm trying to picture is that how to go about predicting a signal coverage. That is why I asked about if it changes the radiation pattern.

This came to mind because from what I read many antenna setups are limited by the laws governing its area of installation. I don't think anyone wants to see a 500ft mast on their backyard. Also, materials would be expensive.

Thanks!


 
   
 
languer
 Post subject:
Posted: Tue Aug 15, 2006 4:17 pm 
 
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Joined: Sun May 14, 2006 8:53 pm
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That's a pretty cool application. There's a small company I know off that works with weather balloons and communication devices. Pretty interesting use of technology.

As far as the antennas, using "groundless" (not technical term) antennas (such as a dipole) will be ok if you maintain some reasonable distance form the ground (far-field comes to mind). The same applies to "grounded" antennas (e.g. monopoles, patches, any "image" antenna), the antenna requires a close ground so you keep the "real" ground away not to disturb the patterns (again far-field comes to mind).

This are the premises for antennas used in aviation, maritime, and pretty much any other elevated type. Good distances become much more manageable with higher frequencies.


 
   
 
Mr.Whatever
 Post subject:
Posted: Wed Aug 16, 2006 10:58 pm 
 
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Speaking of balloon antennas, is the company you have in mind named Floatograph? I've seen some of their products before and it looked very interesting.


 
   
 
sag
 Post subject
Posted: Sun Nov 26, 2006 8:21 am 
 
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Joined: Wed Apr 05, 2006 3:34 pm
Posts: 6
accually, as long as the ground is outside the 3rd order FRESNEL zone the pattern will not change...





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