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billhuntersemail(at)gmail
Guest

Posted: Sun May 22, 2016 12:03 pm Post subject: Ground Plane Question

I have a question about the “Ground Plane” design and the antenna mounting within that ground plane in a composite aircraft:

 

The SkyView manuals states “When a conventional aircraft monopole antenna is used it relies on a ground plane for correct behavior. For ideal performance the ground plane should be very large compared to the wavelength of reception, which is 305 mm. In a metal skinned aircraft this is usually easy to accomplish, but is more difficult in a composite or fabric skinned aircraft. In these cases a metallic ground plane should be fabricated and fitted under the antenna.

 

As the ground plane is made smaller, the actual dimensions of the ground plane become more 

critical, and small multiples of the wavelength should be avoided, as should circles. Rectangles 

or squares are much less likely to create a critical dimension that resonates with the 

transmissions. The smallest practical ground plane is a square around 130 mm per side; as the 

size increases the performance may actually get worse, but will be better by the time the 

ground plane is 780 mm on each side. Anything much larger than that size is unlikely to show 

significant further improvement.

 

So I get that the metal foil/piece needs to be a square that is larger than 130 MM X 130 MM however where should the antenna be mounted in that square?  At the edge, outside corner, or in the exact center?  I would think that the center would not be better than the edge or corner because the wavelength 

..

 

Cheers!!!

 

Bill  Hunter

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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Sun May 22, 2016 4:45 pm Post subject: Re: Ground Plane Question

Mount the antenna in the center of the square.  The numbers that I read on the Dynon website are 120 mm and 700 mm, 120 being ideal.  I could be wrong but do not think that the size is going to make a whole lot of difference, practically speaking.  Sensitive test equipment might see a difference using different sizes of ground planes, but will it make a difference to a radar receiver?

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_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Sun May 22, 2016 5:02 pm Post subject: Ground Plane Question

On 5/22/2016 2:52 PM, William Hunter       wrote:

     

      	  Quote: 	
		                         <![endif]-->   <![endif]-->                

I have a               question about the “Ground Plane” design and the antenna               mounting within that ground plane in a composite aircraft:         

          

The SkyView             manuals states “When a conventional aircraft monopole             antenna is used it relies on a ground plane for correct             behavior. For ideal performance the ground plane should be             very large compared to the wavelength of reception, which is             305 mm. In a metal skinned aircraft this is usually easy to             accomplish, but is more difficult in a composite or fabric             skinned aircraft. In these cases a metallic ground plane             should be fabricated and fitted under the antenna.         

          

As the ground             plane is made smaller, the actual dimensions of the ground             plane become more          

critical, and             small multiples of the wavelength should be avoided, as             should circles. Rectangles          

or squares are             much less likely to create a critical dimension that             resonates with the          

transmissions.             The smallest practical ground plane is a square around 130             mm per side; as the          

size increases             the performance may actually get worse, but will be better             by the time the          

ground plane is             780 mm on each side. Anything much larger than that size is             unlikely to show          

significant             further improvement.         

          

So I get that the             metal foil/piece needs to be a square that is larger than             130 MM X 130 MM however where should the antenna be mounted             in that square?  At the edge, outside corner, or in the             exact center?  I would think that the center would not be             better than the edge or corner because the wavelength                     

..           

            

Cheers!!!           

            

Bill                Hunter         

                    

          

       

     	
     

Hi Bill,     

That text is a bit surprising to me; it's in conflict with stuff       I've read about 1/4 wave antennas and ground planes. There are       surely HAM operators on this list that can give you the formula       for ground plane size, but IIRC, it's approximately the same       radius as the length of the radiating element (antenna). If the       ground plane 'legs' droop, it changes their length slightly. The       stuff I've read seems to say that once you go beyond the       "radius=element" size, there's not a lot of benefit. Check out       these images.     

https://www.google.com/search?q=1/4+wave+ground+plane&espv=2&biw=1920&bih=993&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjDwL2u8O7MAhVW4mMKHQL4DlYQ_AUIBygC#imgrc=_     

The only thing that makes sense to me is the 130x130 dimension,       which would yield roughly the average radius to match a 1/4 wave       aircraft comm antenna.     

The antenna should be at the center of whatever you use for a       ground plane. To use some very non-physics terms, the ground plane       'mirrors' the 1/4 wave antenna, making it think it's a 1/2 wave       antenna. If the antenna is way off-center, it will mess with the       radiation pattern. Meaning it will transmit stronger (farther) in       one direction and weaker in another.

          

Kitplanes Magazine has had several good articles recently about       doing just what you are trying to do. If you're not a subscriber,       I'd suggest you check it out. The current editor is a former NASA       mission control guy who's a homebuilding repeat offender, and the       contributors are getting more impressive almost every issue.     

Charlie

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wdaniell.longport(at)gmai
Guest

Posted: Sun May 22, 2016 5:29 pm Post subject: Ground Plane Question

Cant you use a bob archer antenna. As i understand it these do not require a ground plane

 Will On 22 May 2016 21:13, "Charlie England" <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote: 	  Quote: 	
		                     On 5/22/2016 2:52 PM, William Hunter       wrote:

     

      	  Quote: 	
		                                       

I have a               question about the “Ground Plane” design and the antenna               mounting within that ground plane in a composite aircraft:         

          

The SkyView             manuals states “When a conventional aircraft monopole             antenna is used it relies on a ground plane for correct             behavior. For ideal performance the ground plane should be             very large compared to the wavelength of reception, which is             305 mm. In a metal skinned aircraft this is usually easy to             accomplish, but is more difficult in a composite or fabric             skinned aircraft. In these cases a metallic ground plane             should be fabricated and fitted under the antenna.         

          

As the ground             plane is made smaller, the actual dimensions of the ground             plane become more          

critical, and             small multiples of the wavelength should be avoided, as             should circles. Rectangles          

or squares are             much less likely to create a critical dimension that             resonates with the          

transmissions.             The smallest practical ground plane is a square around 130             mm per side; as the          

size increases             the performance may actually get worse, but will be better             by the time the          

ground plane is             780 mm on each side. Anything much larger than that size is             unlikely to show          

significant             further improvement.         

          

So I get that the             metal foil/piece needs to be a square that is larger than             130 MM X 130 MM however where should the antenna be mounted             in that square?  At the edge, outside corner, or in the             exact center?  I would think that the center would not be             better than the edge or corner because the wavelength                     

..           

            

Cheers!!!           

            

Bill                Hunter         

                    

          

       

     	
     

Hi Bill,     

That text is a bit surprising to me; it's in conflict with stuff       I've read about 1/4 wave antennas and ground planes. There are       surely HAM operators on this list that can give you the formula       for ground plane size, but IIRC, it's approximately the same       radius as the length of the radiating element (antenna). If the       ground plane 'legs' droop, it changes their length slightly. The       stuff I've read seems to say that once you go beyond the       "radius=element" size, there's not a lot of benefit. Check out       these images.     

https://www.google.com/search?q=1/4+wave+ground+plane&espv=2&biw=1920&bih=993&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjDwL2u8O7MAhVW4mMKHQL4DlYQ_AUIBygC#imgrc=_     

The only thing that makes sense to me is the 130x130 dimension,       which would yield roughly the average radius to match a 1/4 wave       aircraft comm antenna.     

The antenna should be at the center of whatever you use for a       ground plane. To use some very non-physics terms, the ground plane       'mirrors' the 1/4 wave antenna, making it think it's a 1/2 wave       antenna. If the antenna is way off-center, it will mess with the       radiation pattern. Meaning it will transmit stronger (farther) in       one direction and weaker in another.

          

Kitplanes Magazine has had several good articles recently about       doing just what you are trying to do. If you're not a subscriber,       I'd suggest you check it out. The current editor is a former NASA       mission control guy who's a homebuilding repeat offender, and the       contributors are getting more impressive almost every issue.     

Charlie

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rlborger(at)mac.com
Guest

Posted: Sun May 22, 2016 5:48 pm Post subject: Ground Plane Question

William,

I too was going to suggest the Bob Archer transponder antenna.  It is a full dipole requiring no ground plane and can be mounted inside your composite (assuming it is fiberglas and not carbon fiber) fuselage at a location of your choice.  The only requirement is that it be mounted in a vertical plane.  I use it for my transponder antenna and it sure seems to work well.



http://www.aircraftspruce.com/catalog/avpages/archer_antenna5.php



Blue skies & tailwinds,Bob BorgerEuropa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP3705 Lynchburg Dr.Corinth, TX  76208-5331Cel: 817-992-1117rlborger(at)mac.com (rlborger(at)mac.com)

On May 22, 2016, at 8:28 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:



Cant you use a bob archer antenna. As i understand it these do not require a ground plane Will

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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Sun May 22, 2016 6:01 pm Post subject: Re: Ground Plane Question

I agree with Charlie.



  And the ADS-B receiver antenna can be mounted in any convenient place away from the transponder antenna.  How about inside of that center tunnel?  It can even be pointed up.  Garmin's GDL 39 is designed to sit on the dash pointed up.

This one does not even have a ground plane.

http://tinyurl.com/120-ADS-B

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_________________
Joe Gores

wrmaxwell(at)bigpond.com
Guest

Posted: Sun May 22, 2016 10:13 pm Post subject: Ground Plane Question

As a 40-year ham, I           endorse Charlie's comments. I can add that placing the           vertical radiator off centre will distort the antenna's           radiation pattern, favouring the ground plane's longest           dimension. Not exactly what you want for best all-round           performance, so best place it in the centre. Drooping the           ground plane's legs below horizontal will slightly increas the           antenna's feed point impedance. I find a 30 degree "droop"           gives close to the desired 50 ohms.     

I also concur with           Charlie's comments about the increasing quality of "kitplanes"           magazine.     



              

Bill

          

     On 23/05/2016 11:03 AM, Charlie England       wrote:

     

      	  Quote: 	
		                On 5/22/2016 2:52 PM, William Hunter         wrote:

       

        	  Quote: 	
		                               <![endif]-->   <![endif]-->                    

I have a                 question about the “Ground Plane” design and the antenna                 mounting within that ground plane in a composite                 aircraft:           

            

The SkyView               manuals states “When a conventional aircraft monopole               antenna is used it relies on a ground plane for correct               behavior. For ideal performance the ground plane should be               very large compared to the wavelength of reception, which               is 305 mm. In a metal skinned aircraft this is usually               easy to accomplish, but is more difficult in a composite               or fabric skinned aircraft. In these cases a metallic               ground plane should be fabricated and fitted under the               antenna.           

            

As the ground               plane is made smaller, the actual dimensions of the ground               plane become more            

critical, and               small multiples of the wavelength should be avoided, as               should circles. Rectangles            

or squares are               much less likely to create a critical dimension that               resonates with the            

transmissions.               The smallest practical ground plane is a square around 130               mm per side; as the            

size increases               the performance may actually get worse, but will be better               by the time the            

ground plane is               780 mm on each side. Anything much larger than that size               is unlikely to show            

significant               further improvement.           

            

So I get that               the metal foil/piece needs to be a square that is larger               than 130 MM X 130 MM however where should the antenna be               mounted in that square?  At the edge, outside corner, or               in the exact center?  I would think that the center would               not be better than the edge or corner because the               wavelength                         

..             

              

Cheers!!!             

              

Bill                  Hunter           

                        

            

         

       	
       

Hi Bill,       

That text is a bit surprising to me; it's in conflict with         stuff I've read about 1/4 wave antennas and ground planes. There         are surely HAM operators on this list that can give you the         formula for ground plane size, but IIRC, it's approximately the         same radius as the length of the radiating element (antenna). If         the ground plane 'legs' droop, it changes their length slightly.         The stuff I've read seems to say that once you go beyond the         "radius=element" size, there's not a lot of benefit. Check out         these images.       

https://www.google.com/search?q=1/4+wave+ground+plane&espv=2&biw=1920&bih=993&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjDwL2u8O7MAhVW4mMKHQL4DlYQ_AUIBygC#imgrc=_       

The only thing that makes sense to me is the 130x130 dimension,         which would yield roughly the average radius to match a 1/4 wave         aircraft comm antenna.       

The antenna should be at the center of whatever you use for a         ground plane. To use some very non-physics terms, the ground         plane 'mirrors' the 1/4 wave antenna, making it think it's a 1/2         wave antenna. If the antenna is way off-center, it will mess         with the radiation pattern. Meaning it will transmit stronger         (farther) in one direction and weaker in another.

              

Kitplanes Magazine has had several good articles recently about         doing just what you are trying to do. If you're not a         subscriber, I'd suggest you check it out. The current editor is         a former NASA mission control guy who's a homebuilding repeat         offender, and the contributors are getting more impressive         almost every issue.       

Charlie

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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