Installing an ELT antenna.

it should.......the standard antenna's supplied with most ELT's are simply
fixed length 1/4" wave antennas.....rubber duck type antennas are also fixed
length 1/4 wave they are physically shorter.......but not......with the OAL
of the antenna being simply coiled for the more "convenient" but less
efficient length
1/4 wave length can be mathematically figured by using the simple formula
One-quarter wave: 246 divided by the frequency in MHz equals the length in
feet
divide this by 12 give you antenna mast length in inches
so...ELT frequency of 121.5 is (246 / 121.5 = 24.29")
One-half wave: 492 divided by the frequency in MHz equals the length in feet
243 MHZ is the same if you use 1/2 wave 492/243.0 =24.29")
and when you consider hand held radios use only the radio itself as the
ground plane you find it does still work....though not as well or efficient
as the fixed length 1/4 wave antenna on a good ground plane..though it is
more convenient than carrying your glider around next to your ear )
tim
Please visit the Wings & Wheels website at:
www.wingsandwheels.com





"Paul Remde" wrote in message
news:EBe_e.371199$_o.9111@attbi_s71...
Hi Tim,

Good points. Do you know if the rubber duck antenna will transmit the
higher frequency signals on 243.0 MHz as from the AmeriKing AK-450 ELT OK?
I'm not an expert on antennas, but I imagine that since it is 2 x the
frequency the antenna is designed for it may work fine.

Thanks,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com

"Tim Mara" wrote in message
...
some years ago I contacted my local FSDO and asked about ELT installation
in my glider..this was long before some SSA sites required them
...knowing the glider did not "require" an ELT to be legal, the question
to the Fed's was "can I install an ELT if it doesn't meet the
manufacturers specifications (meaning antenna installation). I installed
this and several others since not because the FAA or SSA required it.but
because I considered it to be an inexpensive safety feature that I wanted
for myself, and for my loved ones should there ever be a chance it might
be needed. Essentially, the response was very favorable with them saying
"anything you do to promote safety we'll go along with".Now that response
was from MY FSDO (local office). I installed the ELT in the most
professional manner as to location, mounting, and meeting all other
manufacturers requirements, expect, installing a handheld radios rubber
duck antenna on a metal plate for ground plane.....I completed a 337 and
new wt/balance and had the local A&I sign off on the installation..I also
tested the ELT at some range and found the signal to be actually quite
excellent.....Now I never tested it beyond a few miles, and I'm quite
sure a higher performance 1/4 wave fixed mast antenna mounted external
with proper ground plane may have been better.....but this installation,
IMHO did what I wanted and expected.....it would give the S&R people
something to locate the aircraft with....
I also had concerns about externally mounted ELT antenna's being knocked
off in a crash and contacted 3 different ELT manufacturers and found that
even one manufacturer claimed they had certified their brand ELT with NO
antenna installed at all and with the ELT simply sitting on an aircraft
wing when it was tested to be certified. obviously this would not be the
highest performance set-up and not what should be.
I have noted that S-H and DG have made ELT antenna installations in some
gliders that are comprised of nothing more than this same rubber duck
antenna mounted on an angled bracket in the cockpit with essentially no
ground plane........though I do not consider this to be a high
performance set-up, it appears they also think it is
suitable......Personally I wish all glider manufacturers would spend a
bit more time and consideration to building really good antenna's into
their structures for Comm, ELT and Transponders, so far none
have.....until then, we have to improvise.and do the best with what we
have.....that is why I have made some "non-certified" antenna options
available, and though I have tried to make it known these are not
certified for use where the FAA mandates ELT use, they will IMHO work,
and simple and inexpensive "options"......if someone (anyone) has a
better option, I would like to see them....and would of course consider
offering them as well...
Best regards
Tim

Wings & Wheels
www.wingsandwheels.com

"jphoenix" wrote in message
oups.com...
Marc,

Perhaps we could have the SSA government liaison (or SRA dude) ask all
these questions directly to the FAA. Specifically:

Can a private pilot glider install his own ELT in his own experimental
glider and sign it off?
Does a TC'd glider need a 337 form completed and approved (major
alteration)?
Does a glider with an ELT installed have to meet all (or some) of the
requirements of 91.207?

With an official FAA answer to these questions, and perhaps some more I
didn't think of, we can avoid uncertainty over what rules apply and how
they apply, etc.

Jim





I think it is fairly clear that for a glider with an experimental
certificate, you can pretty much install an ELT any way you want, and
likely get away with signing it off yourself (as a non-A&P). I think
it
is also fairly clear that an ELT installation in a type certified
glider
will require at least an A&P (and possibly IA) sign off, but probably
does not require a 337. The question in my mind, however, is whether
the typical A&P (or IA) would be willing to sign off an ELT
installation
in a certified glider, that makes use of uncertified components (like a
rubber ducky). Any A&Ps out there willing to comment?

Marc

Mike the Strike wrote:

Tim's comments are very useful.

I am also wrestling with both ELT and transponder antenna installation
issues and wonder why manufacturers don't install them, at least as an
option.

Schleicher offers transponder antenna installation, as does DG (DG also
has drawings on their website for their gliders that aren't even in
production). Other manufacturers likely also offer this. Check with your
manufacturer about these antennas, if you haven't already.


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

In my ASH-26E, the ELT is located by my left elbow, and the entenna is
the wire whip installed in the baggage area above the spar, as the is
the only non-carbon skinned part of the glider.

I didn't bother with a ground plane as I figure amny chrashed airplanes
also may not have a ground plane to work with...

The antenna is mounted to an aluminum bracket behind my left shoulder,
and curves around the inside of the baggage area toward the rear and
right side. Springiness keeps it nicely pressed against the top of the
fuselage.

As for transponder, I had the factory install it, as the cost was
essentially parts - something like $120 four years ago. I still
haven't installed the transponder itself, but am running the antenna
through a regimen of abuse as it occasionally catches on the trailer.
The antenna is installed through the fuselage just aft of the wheel,
and there is no added ground plane, as I assume the carbon skin is good
enough.

-Tom