---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 09/16/19: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:12 AM - Re: Grounding radio antenna and transponder antenna (Argonaut36) 2. 10:46 AM - Re: Re: Grounding radio antenna and transponder antenna (Robert L. Nuckolls, III) 3. 07:27 PM - Re: Grounding radio antenna and transponder antenna (user9253) 4. 08:37 PM - Re: Grounding radio antenna and transponder antenna (Argonaut36) 5. 08:45 PM - Re: Grounding radio antenna and transponder antenna (Argonaut36) ________________________________ Message 1 _____________________________________ Time: 08:12:04 AM PST US Subject: AeroElectric-List: Re: Grounding radio antenna and transponder antenna From: "Argonaut36" Thanks for your reply. As far as the size of the ground plane, I am constrained by the small dimensions of the airplane. The ground plane should be larger, but there is no much that I can do about it. I try to improve everything else in order to get more range and less static. When you say that antennas do not necessarily have to be grounded to the airframe, you seem to imply that it would be better to ground the antenna, even if it is not indispensable. In my case, because of the ground plane issue, I would take any improvements, doesnt matter how small. Could you please confirm that, ideally, radio antennas should be grounded to the airframe and provide a reference for that (book, website, paper). Thanks Read this topic online here: http://forums.matronics.com/viewtopic.php?p=491316#491316 ________________________________ Message 2 _____________________________________ Time: 10:46:45 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Grounding radio antenna and transponder antenna You said tube structure . . . fabric or metal skin? If fabric, a 5.6" alum disk .060 or so thick is an appropriate ground plane. Emacs! If your fabric is 'tight' against a structural tube, then the ground plane can go on the outside surface. It would look cleaner if between skin and tube. One or more clamps should secure the ground plane to structure . . . not for electrical 'bonding' but for mechanical support. Emacs! Whether the ground is inside or outside the skin, the antenna should mount in the center with good electrical connection between antenna base and the ground plane. If metal skin, simply mount antenna to skin but consider double of any practical size to re-enforce the mounting surface to preclude cracking around mounting hole due to aerodynamic buffeting. VHF comm antennas need good support to the ship's tubular structure. If metal airplane, ground antenna base to skin. If fabric covered airplane, ground a suitable mounting plate to the ship's structure then ground antenna to the mounting plate. Ship's structure becomes the ground plane. Bob . . . ________________________________ Message 3 _____________________________________ Time: 07:27:16 PM PST US Subject: AeroElectric-List: Re: Grounding radio antenna and transponder antenna From: "user9253" Bob N. posted today "One or more clamps should secure the ground plane to structure . . . not for electrical 'bonding' but for mechanical support." In my opinion (I am no antenna expert), it is not necessary to connect an antenna ground plane to the airframe. However, the airframe could be used as a ground plane if of sufficient size and shape. Radio frequency current and DC current behave entirely differently. What is an open circuit to DC could be a short circuit for radio frequency current. An antenna ground plane does not necessarily have to be straight or flat. Nor does it have to be a sheet of metal. Curved strips of wire or metal tape that radiate outward from the antenna base could serve as a ground plane. Experiment to find something that works. http://www.aeroelectric.com/Reference_Docs/Antenna/ - "ARRL Antenna Book" The 2 meter band is close to the aviation band. - https://ia801600.us.archive.org/7/items/TheArrlAntennaBook/Hall-TheArrlAntennaBook.pdf[ -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=491322#491322 ________________________________ Message 4 _____________________________________ Time: 08:37:46 PM PST US Subject: AeroElectric-List: Re: Grounding radio antenna and transponder antenna From: "Argonaut36" Bob, Thanks for your post and for the sketch. Please note that my airplane has a standard certificate. It is not experimental. The antenna is mounted on a removable panel on the bottom of the airplane; the antenna was installed professionally on the panel and I have not had any structural problems in many years of flying. The panel is made of metal except for a plexigas window and doubles as the radio antenna ground plane, even if it is kind of small for that purpose. I have installed some metal tape that goes over the plexigas trying to improve things. The panel is attached to a vertical metal panel on each side with machine screws/anchor nuts. At the front, the panel overlaps another metal panel and connects to a little beam with sheet metal screws. At the back, the panel overlaps a fabric panel and connects to a little beam with sheet metal screws. As mentioned above, this panel is removable and needs to come out of the airplane for maintenance purposes a few times a year. It would be difficult to make modifications to this panel. I have noticed that the transponder antenna ground plane is grounded to the plane tubular frame and I am just trying to establish if the radio antenna panel should also be grounded or not and why. Thanks for your help. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=491323#491323 ________________________________ Message 5 _____________________________________ Time: 08:45:44 PM PST US Subject: AeroElectric-List: Re: Grounding radio antenna and transponder antenna From: "Argonaut36" Many thanks for the additional information provided. I will go through the documents linked to your post. Please note that I have included additional information on my antenna set up in my reply to the post of Bob. 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