ELT Antenna location

Fred Fagan · Post by **Fred Fagan** » Fri Aug 10, 2007 6:59 am

I am building the RV-9 TD, with sliding canopy and I am installing an Ameri-King model AK-450 ELT in the left side of my baggage area under the the cover between the floor stiffeners. My question is has anyone installed this ELT in your RV-9 or RV-7 in the same location and if you did where did you install the external antenna?

Thanks for the help

Fred Fagan
Wings,Empannage complete
Fuselage working

captain_john · Post by **captain_john** » Fri Aug 10, 2007 7:23 am

Hi Fred!

I haven't installed it yet, but I do plan on putting it in similar to what you have explained. Installation between the floor ribs is a good idea, IMHO. I have made some access panels there and will probably do the same. If not, I will simply place it behind the passenger.

As for the antenna, I am doing the tip up. I plan on installing the antenna along the back of the roll bar and clipping it to the roll bar as it curves along the canopy.

CJ

Post by **Spike** » Fri Aug 10, 2007 9:11 am

That seems to be a popular place for the antenna.

cjensen · Post by **cjensen** » Fri Aug 10, 2007 9:28 am

That's where my antenna will go as well! The box will go behind the seat, on top of the floor.

The other popular spot for the antenna is at the intersection of the horizontal and vertical stabilizers.

Fred Fagan · Post by **Fred Fagan** » Fri Aug 10, 2007 10:14 am

The antenna will work well behind the roll bar on the sliding canopy ( one advantage of the tip up canopy) but will not work on the sliding canopy. I did like the idea of location between the Horizontal and Vertical stabilizers. Can the antenna be located inside an enclosed area like that?

Post by **Spike** » Fri Aug 10, 2007 10:17 am

I have a good friend that located it there on his 8A. Its right underneath the fiberglass emp. fairing.

John

tmbg · Post by **tmbg** » Fri Aug 10, 2007 10:18 am

just out of curiosity, has anyone looked into the performance of the antenna with the proximate coupling of the steel roll bar it's clipped to? The roll bar is longer than the antenna, making it a reflector, which could direct the radiation pattern back toward the interior of the airplane and the ground.

captain_john · Post by **captain_john** » Fri Aug 10, 2007 6:33 pm

Ian, that is exactly right!

I prefer the loss of performance over having it on the exterior skin.

As far as locating it under the emp fairing, if you do that it has to be oriented horizontally. I have heard that some DAR's will not allow that.They tell me that there is something written somewhere that says it has to be vertical so that in the event it has to work, it will properly emanate it's signal in the upwards direction. Well... I suppose that is fine of you end up right side up after all is said and done!

CJ

tmbg · Post by **tmbg** » Fri Aug 10, 2007 9:02 pm

that would probably have more to do with vertical polarization of the signal.

man, all that antenna design crap I learned years ago is finally becoming useful.

OH btw, while we're talking about antennae, I have an antenna analyzer if anyone is doing work fabricating antennae and needs to borrow one

jim_geo · Post by **jim_geo** » Fri Aug 10, 2007 9:15 pm

Well... it aint a steel roll bar. It's aluminum.

By the way for QB this is not a straight forward piece of work.

tmbg · Post by **tmbg** » Fri Aug 10, 2007 10:56 pm

aluminum makes just as fine a reflector as does steel

captain_john · Post by **captain_john** » Fri Aug 10, 2007 10:58 pm

Yup, it do!

Very eloquently stated, Ian!

RF don't care! Metal is metal!

CJ

tmbg · Post by **tmbg** » Sat Aug 11, 2007 2:22 am

don't get carried away there, CJ, RF doesn't get along with some metals too well.... like lead or mu-metal

captain_john · Post by **captain_john** » Sat Aug 11, 2007 4:15 pm

Okay, you got me now. What is mu-metal?

CJ

tmbg · Post by **tmbg** » Sat Aug 11, 2007 6:35 pm

High nickel alloy that has very high permeability, which makes it an effective screen for magnetic and electromagnetic fields. It's used for shielding.

jim_geo · Post by **jim_geo** » Sat Aug 11, 2007 7:49 pm

Frankly if you need the ELT probably where ever you put the antenna will be the wrong place. Since I have a nose wheel I'm going to put mine on the bottom of the fuse. Ya pays yo money and ya takes yo chances.

captain_john · Post by **captain_john** » Sat Aug 11, 2007 8:29 pm

jim_geo wrote:Since I have a nose wheel I'm going to put mine on the bottom of the fuse.

Jim, now THAT is FREAKIN' FUNNY!!!

You made me laugh out loud!

CJ

svanarts · Post by **svanarts** » Sat Aug 11, 2007 11:43 pm

My antenna runs up one side of the rear passenger seat. I asked the real-live FAA inspector who inspected my plane if that's okay or not. He said it didn't really matter where I put the antenna because if I hit something hard enough to make it go off it wouldn't really matter how long it took to find me. Nice guy.

Dan A · Post by **Dan A** » Sat Aug 11, 2007 11:51 pm

I put my ELT antenna in the empenage under the verticle stab. LIke has been just stated, If I go down and it goes off it probably won't matter!

Dan