C

Chappyd

Well Known Member
I bought my ELT, an EBC unit from AFS a while back, and have now gotten to the point where I'm doing the install. Since the whole 406/121.5 thing is going on, I decided there was no point in getting the old style 121.5 and sprung for a new 406 unit. Not knowing much about ELT's, I bought the EBC-406AP becuase it was the least expensive of the units listed for sale on AFS's web site.

http://www.aircraftspruce.com/catalog/avpages/ebc406.php

(at the time it was one of the cheapest :) ) I really like the ability to remove it and take it with me should I need to exit the aircraft, and it looks really robust. However, it must be mounted in the cabin, so after thinking about different locations, I came up with this one in the baggage area. I fabricated a mount that ties into the longeron and skin stiffners. I think I should still be able to install the Classic Aero interior I want to. Hard to tell by just the pictures. The black arrow indicates proper orientation for the direction of flight


elt.jpg


My dilemma at this point is where do I want to put the external antenna. I've done searches on this site, and read about folks different choices for antenna location. Since apparently the antenna can "see" through non metallic parts, ie the tail fairing, canopy, etc. I'm thinking about placing it in the baggage area also behind the flap motor area. The top of the antenna would stick up a few inches over the seat back rail/crossmember, but would easily bend out of the way for loading stuff if need be.


ant.jpg


I would fabricate a mount that would put the base of the antenna a couple of inches above the baggage floor. Would this work ok? Do I need to have a ground plane as mentioned in the manual? How big would the ground plane need to be? It's either here or mounted on the top of the fuse behind the canopy. The antenna cable is 6' and they say to keep it this length or shorter.

Thoughts & suggestions welcome :)
 
What if you flip upside down?

This is something I've stewed about a lot. There doesn't seem to be a good answer.

They say it is supposed to be mounted vertically with access to the sky, but if you flip upside down, its going to be badly shielded. I figure, if the plane stops right side up, I'd like help eventually. If the plane stops upside down, I need help NOW.
Putting it in the tail fairing means its not vertical, and still has better sky visibility right side up than upside down.
Heck I don't know, I've heard stories of ELT signals being traced to discarded units with NO antenna, buried in a land fill.

This shows fiberglass airplanes are good for something!:D
 
Yep....

scsmith said:
....Heck I don't know, I've heard stories of ELT signals being traced to discarded units with NO antenna, buried in a land fill.

This shows fiberglass airplanes are good for something!:D
Click to expand...

We had the CAP show up at our airpark when a passing CAP Cessna picked up a weak ELT signal.

After a long search, we worked out it was a local A&P doing an annual walking about with an "on" ELT in his hand (no antenna) - he should have known better, since he was ex-CAP...:rolleyes:

Signal strength on 121.5 is low with no antenna, but it does radiate....:)

However a loose "on" ELT in a Bonanza parked under a metal shade port got no attention for 12 hours until our airpark manager returned to his house and noticed it on his scanner - at 500 ft range.
 
I can appreciate that nobody wants extra antennas sprouting from their sleek airframes, but if you have to have just one antenna protuding, the ELT antenna should be the one. Here's why...

Firstly, metal structure causes the ELT signal to be reflected, causing an omni-directional antenna to sometimes become quite directional. Installing the antenna in the baggage compartment or other similar area is simply not a good idea for this reason alone. Same goes for a fancy installation hiding it under fibreglass fairings near the tail. The metal structure of the tail will cause it to be very directional. If the search party happens to be approaching from the direction where metal structure has caused a null in the radiation pattern then you're not going to be found. Years ago I conducted a series of tests on a helicopter in an attempt to determine where we could mount an antenna. The effect of metal structure on radiation pattern was much more extreme than I would ever have thought it to be.

A ground plane is an absolute necessity if you want the antenna to effectively deliver signal to the sky.

The second reason why you want the antenna mounted atop the fuselage is that it actually gets pretty good protection there in the case of a nose-over, thanks to that nice big vertical fin acting as a roll bar.

I wish the particular 406MHz ELT you've selected was approved for use in Canada as it is what I would like to have installed. As it is, I ended up going with the Artex ME406, one of only two "inexpensive" 406MHz ELT's certified for use in Canada. The other one, the Kannad Compact, wasn't certified at the time I did my installation, so I had a field of exactly one approved ELT to choose from. Gotta love tough decisions like that!
 
Kannad ELT antenna

Dear fellow builders,

I have the Kannad Integra installed in my Vans RV8.
Months ago I contacted Kannad to find out for the best suitable antenna. The recommendation was the ELT10-773-3. The version I have is S/N 10363.
After performing the self test, the radio starts with a long beep (according manual) followed by three short beeps and another 5 short beeps, indicating a VSWR problem with the antenna (as far as I understood the manual).
The antenna cable between the unit and the antenna measures 130 cm.
I tried the portable antenna for the Integra, directly installed on the unit. That antenna worked properly, no alerts. I changes the antenna cable, no result. I tried the 10-773-3 with a different antenna cable, same fault.

Ideas, solutions, faults????

Best Regards from Bavaria

Thanks for answering
Stephan
 
Dave,
I just dealt with this issue a few days ago. Just like everyone else, I did not want another antenna sticking out of my airframe. But after it was all said and done. The requirements said to properly work, it had to be on the outside of a metal aircraft. I did not want to spend $600 on a 406 ELT and then negate the benefits by mounting the antenna in the wrong place.

My advice (free, and worth that much) you spent the money for the 406, mount the antenna in a location that meets the installation requirements.

Good luck.
 
OK... some thoughts. The 406 emits a high power pulse. Very brief. Like a transponder sort of. If you look at the current draw of a transponder, it is low. But puts out 200 watts. My Sandia STX 165 just measured 997 watts effective radiated power on a $60K Aeroflex tester yesterday.
The new ELT's do the same. They spit the ID and the LAT LONG as well, if GPS equipped. Civil Air Patrol cadets are going to be walking around with a 1920's directional antenna. So, the question is: Do you want to be saved? Do you just want your body parts to get back to your spouse for proper burial?
If you are dead... no hurry. They found Steve Fossett eventually.
The antenna mounted externally can and will break in some crashes. Consider that if you are conscious... you can flip the switch on an EPIRB in your pocket. Deploy the spring antenna and turn it right side up. The pulse WILL hit a the rescue sat. most likely.
IF your onboard 406 has an in-cabin antenna... it probably is intact also.
They are a high freq. signal... a ground plane for the little antenna can come from the metal surrounding it. Signal will be in excess of 5 watts. Thousands of times stronger than your old 121.5 pumping out millwatts. If you choose an external antenna, mount it where you think it might survive.
All ELT's now require a panel mounted activation switch. We are most relluctant, (males anyway) to ask for directions or help. In the case of a gliding RV, I respectfully suggest you reach over and turn that switch on.
Get your tax monies worth from the government. You are more effective than any G switch. If it turns out that muddy slug of rainwater goes on through and the fan starts making noise again... just switch the ELT off.
Better to explain than rot while the coyotes circle. You folks have a Merry Holiday. PEACE
 
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