Antenna Locations. 3 installed,comm,trspdr,ADSB
Heres my update on locations for the antennas. I was in contact with a half dozen or so shops. What I learned is reciting one statement I use to myself. How did you DO that and WHY did you DO that that way. None of the shop owners would commit to HOW the antenna was mounted by WHY! Found my answer in my own thoughts. So my WHY thoughts were based on the reading material from the manufacturer of the antenna and Bob Nuckles book Aero Electric. ( buy on Amazon.com). As one owner said you need to understand the integrity of your location,that is thickness of the metal,interference from exhaust, is there flaps,gear,top of plane, does the surface block signals you are seeking? With that all said, I sat down and considered like a engineer the foundation of this project. Two of my 3 locations required doubler plates because I could push in of the bottom skin and make significant movement. What I did not want was oscillation that went into convergence. Example as I remembered in a demo where a stop sign on a post in high wind oscillation back and fourth until the failure would happened at the base of the post or at the mounting point on the sign to the post. I went with my comm antenna 5 inches right of the center line of the bottom and just behind 4" behind the rear baggage bulkhead. If I did it again I would put it in UNDER the baggage floor. ( for you new builders I would recommend putting nutplates in to hold the floor down and NOT rivets as the plans call for) Drilled out ALL the rivets in the baggage floor panel to make antenna (RG400 ) cable run to the front by installing plastic pass thru bushings. Installing these bushing when the floor is not riveted down is always a GOOD option. I would recommend that! My doubler plates were Alodined as well as the surface I riveted to.
My ADS-B location on the RV9A is forward of the spar and under the gear weldment.About 7" in from the side of the fuselage. The transponder antenna I put aft of the firewall 4" on the left side and 3" from the left side of the fuselage. Are all the locations perfect? not sure but they are secure. My comm antenna length from my paper work ( not sure if I read it in 43.13 book) recommended to not go over 10.5 feet for best coverage. I don't know and if any longer distance makes a noticeable difference.
Recently I listened on my Portable ( I-Com A-6 ) as my friend called tower for landing instructions from 40 miles from me. Mine is where his is and I called it good. Made sure connections at the doubler plates and antenna mounting screws would make the surface a good ground plane.
The other pain was making brackets to hold my cables and it was a feat at 8-10" at a time til I got to the radio. I like my installation,would I work at a avionics shop? The short of the answer would be NO, the shop would only turn a profit the first month or until the my first customer received his bill!. At which time I think I might be looking for a new employment! You just got to love building. WOOT WOOT! Thats my story and if you engineers ( RV Builders) out there can clarify or correct some of my story so be it as I would be enlightened.
Always appreciate VAF members conversations!
Ron in Oregon
