---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 12/09/18: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:30 AM - Re: Bob Archer comm antenna dimensions ? (GTH) 2. 07:25 AM - Re: Bob Archer comm antenna dimensions ? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 04:30:19 AM PST US Subject: Re: AeroElectric-List: Bob Archer comm antenna dimensions ? From: GTH /Le 09/12/2018 06:26, The Kuffels a crit: / > // > // > // > /What model Archer antenna does your friend have. Archer offers a > compressed dipole (looks like a weird "3") model SA006 which is 26.5" > tall by 12" wide./ > // > // Hi all, Thank you to all who answered. My friend's model is the SA001A. He just mentionned the SA006 which could have been used, but he has already received the SA001A. Here are some info about the present project : It is a very small airplane, in the 100hp/140kt cruise category. The fuselage is carbon fiber, with the fin, rudder post and rudder intentionally made of glass fiber (shown in red below) : We will try to "unbend" the radiating element to have it more perpendicular to the base/ground element and fit in the tail fin, and as advised I'll borrow a SWR-meter to verify this does not harm the antenna efficiency. Our intention is to use the same principle as in our first project to connect the antenna ground element to the carbon fuselage. Concerning this first project, still flying - and transmitting - great after 15 years. At the time Bob Archer kindly answered our many questions, and here is how we installed the antenna with great success : The antenna is located in the right wingtip, intentionally made of glass instead of carbon as the rest of the airplane : saumon Mr Archer told us that would could "unbend" the radiating element to match the wingtip shape. He also gave his advice on how to connect the ground element to the wing carbon skin : http://contrails.free.fr/images/instruments/Alum_Foil.gif Thank you for your help, -- Best regards, Gilles http://contrails.free.fr http://lapierre.skunkworks.free.fr ________________________________ Message 2 _____________________________________ Time: 07:25:06 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Bob Archer comm antenna dimensions ? At 11:46 AM 12/8/2018, you wrote: >Hi all, > >Some 15 years ago we ordered a Bob Archer comm antenna for >installation in our wingtip, and have been very satisfied with it. > >Here is a sketch of our 15 year old antenna : > >[] > > >A buddy of mine launches into another project and just received a >new Archer antenna to install in his tail fin, but the dimensions >and shape seem different, and the rivets prevent the upper segment >from being swept up to fit into the tail. > >Although the antenna is labelled "Comm", we are finally not sure the >model is a VHF one. > >Does any of you gentlemen have any information as to the shape and >dimensions of the present time Archer comm antennas - or VOR >antennas - so we could clarify the matter ? > Antennas come in a constellation of shapes and sizes tailored FIRST to be efficient at the transmission/reception of radio energy. The antenna you've cited was originally a VOR antenna designed to mount under the wing tip of an RV. [] The short, horizontal section riveted to the close-out rib of the wing. It's essentially a bent, 1/4 wave radiator with a 'gamma match'. Further, due to it's operational orientation wtih the earth, it's fundamentally a horizontally polarized antenna. https://tinyurl.com/ycxlsd4d Later in Bob's OBAM aviation efforts, he offered a slightly smaller (Comm frequencies) version (1A) https://tinyurl.com/y9xenkj6 but it too was intended for use on METAL aricraft with non-metallic fin/tip caps. When this antenna is installed on the wing, it's deficiencies as a horizontally polarized antenna are partially offset by attaching the base in the lowest practical orientation on the rib and deflecting the radiating element upward until flush with the upper, inside surface of the wing tip fairing. Many builders have reported good results with this compromised configuration as a COMM antenna. Nonetheless, this antenna is not suitable for use on a totally composite aircraft as it depends on metallic structure for a ground plane. 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