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Antenna radiation pattern - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


 Post subject: Antenna radiation pattern
Posted: Mon Aug 14, 2006 1:07 pm 
Captain
User avatar

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?


 
   
 
 Post subject:
Posted: Mon Aug 14, 2006 3:57 pm 
 
Captain
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Joined: Sun May 14, 2006 8:53 pm
Posts: 17
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?


 
   
 
 Post subject:
Posted: Tue Aug 15, 2006 9:49 am 
 
Captain
User avatar

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!


 
   
 
 Post subject:
Posted: Tue Aug 15, 2006 4:17 pm 
 
Captain
User avatar

Joined: Sun May 14, 2006 8:53 pm
Posts: 17
Location: Earth
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.


 
   
 
 Post subject:
Posted: Wed Aug 16, 2006 10:58 pm 
 
Captain
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Joined: Fri Apr 07, 2006 6:10 pm
Posts: 18
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.


 
   
 
 Post subject
Posted: Sun Nov 26, 2006 8:21 am 
 
Captain

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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