ELT antenna inside sliding canopy???

Good evening fellow RVators,
I am thinking about installing my 406 ELT antenna inside the sliding canopy of my RV. Has anyone out there followed this path? I would appreciate your observations, advice, and a picture or two. Thanks.
John Van Lieshout

I did the same

I installed the ELT antenna on top of the cargo sidewall cover, where the plan calls for tie down ring storage.

We installed our under the tail vert/horiz fiberglass cover.

RV-9 installed ELT antenna through the baggage bulkhead. This points the antenna forward and up along the baggage area side.

Slider ELT antenna mount

http://www.vansaircraft.com/pdf/revisions/RV-12/Section_42.pdf
The RV12 does it. Look near the bottom of this document for the mounting drawings. Page 42-16.

Gary

My 406 ELT ant is mounted on the intersection of the left canopy rail and the seat back cross bar ( 6 slider) right behind the pilots left shoulder. I used the angle of the mount and a bit of slight bending to get it to conform to the curve of the turtle deck. I fabbed a little retainer bracket to hold the tip, using a piece of plastic tubing on the tip to hold the gentle curve and provide insulation

I know that this ant works. It was picked up once by the SAR Air Force rescue center from inside my hangar (wooden roof) during about 20 seconds of inadvertent activation during a test. ..... Nice folks to chat with but I suggest you don't unless necessary!

Chasing an unmeasureably small knot of drag reduction I don't believe is as important as building an easy-to-live-with airplane. An antenna inside the canopy is one more thing to snag when reaching around inside, potentially damaging the antenna and the snagee.

Keeping the ELT and antenna in close proximity so the antenna cable isn't passing through bulkheads is a good idea, and why many get put in the tail cone. In what orientation the wreckage will settle after cartwheeling is anybody's guess, so I'm not particular about top or underneath the saddle fairing, though the latter is obviously less visible to satellites. Put the antenna on top, behind the slider rail, paint a light coat of body color (where is says "do not paint"), you'll stop seeing it, and it's likely the best location all things considered.

John Siebold

Great info posted here so far. Here are some other things to know about 406. It is a 5 watt data burst. Sent about every 50 seconds or so depending on manufacturer. It contains the unique ID that you have registered with NOAA.
You can test any ELT in the first five minutes after the hour... for a few seconds. In the 121.5 era... these signals were common just after the hour and towers, airliners etc. ignored them.
Now, the test function... when done according to the directions, won't send any real signal out. But, it will do a software and hardware test and report the results to you. It also logs this event in most units as time used against total battery life. Enough test time is built into the battery reserve to do tests monthly until the battery expiration date. As mentioned, the antenna orientation is less important than you might think. G switch activation is still primitive. It may not activate at all. Most have a sound alert now. If you are down and conscious.... waiting for help... listen for the tone. If you don't hear it, activate with the panel switch. With built in GPS, the rescue coordination center will know who you are and where you are right away.

gereed75 said:

My 406 ELT ant is mounted on the intersection of the left canopy rail and the seat back cross bar ( 6 slider) right behind the pilots left shoulder. I used the angle of the mount and a bit of slight bending to get it to conform to the curve of the turtle deck. I fabbed a little retainer bracket to hold the tip, using a piece of plastic tubing on the tip to hold the gentle curve and provide insulation.

Click to expand...

I did the same thing but put it on the right side where the slider track and seat rest bulkhead meet. In addition, I have the ELT unit right behind the passenger seat and forward of the flap actuator tube, so the antenna cable does not need to pass through any bulkheads that could sever the cable in event of a crash. Further, FWIW, I was not convinced that the bracket Van's provides for the standard aft-of-the-baggage bulkhead position has the stiffness that my ELT manual said was required, plus I feel more comfortable having immediate access to the ELT should I become marginally incapacitated and unable to get behind the baggage bulkhead. Having said all that, I can't say whether it will transmit better or worse from that location.

Here is the picture

Here is how I mounted in a RV-7 slider.

flightlogic said:

Great info posted here so far. Here are some other things to know about 406. It is a 5 watt data burst. Sent about every 50 seconds or so depending on manufacturer. It contains the unique ID that you have registered with NOAA.
You can test any ELT in the first five minutes after the hour... for a few seconds. In the 121.5 era... these signals were common just after the hour and towers, airliners etc. ignored them.
Now, the test function... when done according to the directions, won't send any real signal out. But, it will do a software and hardware test and report the results to you. It also logs this event in most units as time used against total battery life. Enough test time is built into the battery reserve to do tests monthly until the battery expiration date. As mentioned, the antenna orientation is less important than you might think. G switch activation is still primitive. It may not activate at all. Most have a sound alert now. If you are down and conscious.... waiting for help... listen for the tone. If you don't hear it, activate with the panel switch. With built in GPS, the rescue coordination center will know who you are and where you are right away.

Click to expand...

A couple of corrections to offer here, if I may...
1) most current 406MHz ELTs do indeed transmit during the self-test. As an example, the Kannad 406Compact transmits sufficiently long on 121.5 to produce two of the characteristic audio sweeps we're accustomed to hearing. Sometimes a VHF comm radio won't break squelch fast enough to catch this brief burst so I advise to manually break squelch on your VHF receiver prior to commencing ELT self test. This way it's certain you'll hear the two audio sweeps. Just make sure the radio volume is set low enough that you can also hear the buzzer (audio alerter) on the ELT during the test.

2) 406 ELT's do indeed transmit a burst of data encoded on the 406MHz signal during self-test. This burst of data has a validity bit which is set to an invalid, or "test" state, for the purposes of self-test. This prevents scrambling of SAR assets but still produces a signal which can be used for complete end-to-end system test, right to the ground earth station. Note that if you should allow self-test to extend past 50 seconds, that validity bit will be set to "valid" and you WILL be sending a real distress message.

Canadian_JOY said:

2) 406 ELT's do indeed transmit a burst of data encoded on the 406MHz signal during self-test. This burst of data has a validity bit which is set to an invalid, or "test" state, for the purposes of self-test. This prevents scrambling of SAR assets but still produces a signal which can be used for complete end-to-end system test, right to the ground earth station. Note that if you should allow self-test to extend past 50 seconds, that validity bit will be set to "valid" and you WILL be sending a real distress message.

Click to expand...

Does the validity bit mean one could test a 406-only ELT any time, or does the 5 min past the hour rule still hold?

Also, are test transmissions logged so one can tell if the sat picked up the transmission and sent it to the ground station?

The five minute rule still applies because the 121.5 ELT signal is still transmitted.

Norman CYYJ said:

The five minute rule still applies because the 121.5 ELT signal is still transmitted.

Click to expand...

I am speculating about a 406 MHz ELT without 121.5 MHz. I guess most 406 ELTs retain 121.5 for "homing only".

Does that mean when and if an FCC "ban" on 121.5 MHz ELT's goes into effect, early adopters get to replace their dual 406/121.5 units? Or figure out how to disable the 121.5 transmitter without also disabling the requisite technically standard orderliness required, even for Experimentals....

I sort of answered my other question myself. There's at least one web-based service to confirms that 406 MHz self-test bursts were received by a satellite and ground stations. But it's 30 bucks to set up and another 30 annually.

I doubt very much that the 121.5 will be eliminated. The SAR guys need a signal to home in on, the 121.5 is what they need and use. The 405 is done in bursts that you can't home in on because they are not a continuous transmitted signal.

A few more thoughts...
1) Test ELT's in the first 5 minutes of the UTC hour, irrespective of their primary operating frequency. (I just learned something new today. I work in the telecoms industry and discovered that 911 testing in one Canadian province can only be done at a specified time on one day of the week. Seems aviation isn't the only world where this kind of limitation exists.)

2) Yes, absolutely, the 406 test signal can be used to do end-to-end testing. I've given thought to subscribing to one of the web-based services for that very purpose.

3) 121.5 is still used for "homing", whether it's by airborne or foot search. The last notes I have from RTCA don't show any movement on inclusion of the 121.5 signal - it looks like it's here for quite a while to come.

4) The FCC "ban" is intended to limit the "primary" transmitting frequency of the ELT, not the secondary which is currently how the 121.5 signal is classified on 406MHz ELTs

5) Between 15 & 20 years ago I worked for a company which produced several working prototypes of man-pack 406MHz homing devices for use by ground searchers. Having seen the results of testing conducted on hidden 406 test beacons I can say with certainty that a 406 homing device not only is possible but should be widely developed for field deployment. The problem is that governments don't want to spend any $$ for new homing equipment. It's much easier for them to pass regulations which require rich airplane owners to re-equip!