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bcollinsmn

Joined: 17 Aug 2008
Posts: 23
Location: St. Paul, MN.

Posted: Sat Nov 15, 2008 2:33 pm Post subject: ARTEX 406 ELT in a 7A

I'm interested in seeing pix of people's installations of the Artex 406 ELT in a 7A. Where it's mounted, for example. Also, if I read this correctly, the antenna requires a 24" ground plane. Seems to me I've seen people use the whip antenna around the back of the rollbar. I assume it's mounted on the gusset that connects the 705 bulkhead to the longerons (with the gizmo for the tip-up latch.) But how are you accomodating a 24" ground plane there?



Thanks



Bob Collins

RV Builder's Hotline

http://rvbuildershotline.com/

_________________
Bob Collins
St. Paul, Minn.
RV-7A - Running wires
http://rvbuildershotline.com
Day job: http://minnesota.publicradio.org/collections/special/columns/news_cut/

Charles Heathco

Joined: 10 Jan 2006
Posts: 201

Posted: Sun Nov 16, 2008 5:12 am Post subject: ARTEX 406 ELT in a 7A

Bob, read your question with interest. Sounds like  this 406 takes a different setup than the current ones being used? You cant  install it same as the ones we are using? Chalrie H

   [quote][b]

bcollinsmn

Joined: 17 Aug 2008
Posts: 23
Location: St. Paul, MN.

Posted: Sun Nov 16, 2008 7:25 am Post subject: Re: ARTEX 406 ELT in a 7A

Yeah, I think you can. According to the instructions, the mounting bracket will exchange properly with the existing setups. I'm just curious how people are installing. When you read the instructions, it sounds like they want it as far in the tail as possible with the antenna having this 24" ground plane. But when I've seen various installations, it's tucked under the baggage compartment quite often with the whip antenna bent around the aft side of the rollbar.



According to the instrx, whatever is used, the ELT and the antenna should be in the same "bay". Van's sells that combo ELT/Strobe power supply bracket (which I used for the strobe) that fits on the stringers, but  that will only fit directly behind the 706 bulkhead.



It's not big deal, I'm just interested in seeing various permutations before I dive in.

_________________
Bob Collins
St. Paul, Minn.
RV-7A - Running wires
http://rvbuildershotline.com
Day job: http://minnesota.publicradio.org/collections/special/columns/news_cut/

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Sun Nov 16, 2008 10:52 am Post subject: ARTEX 406 ELT in a 7A

Bob, I am hoping that this thread actually expands and becomes a Big

Deal, or at least bigger.



I have felt for some time that the location, mount orientation, ground

plane and attempt at concealing the antenna actually leads to an

ineffective or nearly worthless electronic device.  That premise was

based on the 121.5 variant not the 406 however, because one build might

have mounted it incorrectly, scores follow suit and then  the masses

drink the Kool-Aid.  I have always concluded the function might not be

important, only its presence for the DAR signoff.



I have remained curious how many rescues rather than recoveries "after

the fact" are attributed to a properly functioning signal and a

responsible response by the parties that monitor the frequency (either

121.5 or 406.



As a ham (amateur) radio license holder this pursuit of concealing the

antenna has always been fascinating.  Do any of the readers have signal

propagation graphs on signal strength radiating from inside the tin can?



John Cox

Aurora, OR



--

acepilot(at)bloomer.net
Guest

Posted: Sun Nov 16, 2008 11:11 am Post subject: ARTEX 406 ELT in a 7A

Well, I don't have data to back me up, but as a fellow ham who dabbles 

in the world above 50 MHz (actually, I have stuff for our microwave 

bands) and can say that a fuselage would make a "decent" waveguide at 

VHF and UHF.  Waveguide is made to contain RF.  I think putting antennas 

INSIDE of a metal container is just asking for it not to radiate to the 

outside world when you need it most   I've often wondered why some 

folks get so bent over an external antenna that may cost them a knot or 

two.  For God's sake, you're going 160 knots in an RV, what's 158 

knots?  How fast does one need to go?  Take it from me, my present ride 

cruises at 65 knots or so...I'd be more than happy with 158 



Scott



John Cox wrote:



[quote]



Bob, I am hoping that this thread actually expands and becomes a Big

Deal, or at least bigger.



I have felt for some time that the location, mount orientation, ground

plane and attempt at concealing the antenna actually leads to an

ineffective or nearly worthless electronic device.  That premise was

based on the 121.5 variant not the 406 however, because one build might

have mounted it incorrectly, scores follow suit and then  the masses

drink the Kool-Aid.  I have always concluded the function might not be

important, only its presence for the DAR signoff.



I have remained curious how many rescues rather than recoveries "after

the fact" are attributed to a properly functioning signal and a

responsible response by the parties that monitor the frequency (either

121.5 or 406.



As a ham (amateur) radio license holder this pursuit of concealing the

antenna has always been fascinating.  Do any of the readers have signal

propagation graphs on signal strength radiating from inside the tin can?



John Cox

Aurora, OR



--

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Sun Nov 16, 2008 11:37 am Post subject: ARTEX 406 ELT in a 7A

My premise remains that after the first ineffective install, others

followed by copying, Kool-Aid was passed, really large numbers of

installs supported lack of viable research.  The device is aboard, which

meets the letter of the law - Chapter Closed.  Practical value - Zilch.

With 406 the discussion deserves to be opened to location within the

aircraft, purpose of the device, mounting technique, ground plane

effectiveness and strong signal propagation (on freq) from a good

distance from the aircraft fuselage regardless of location, orientation

or condition of the airframe.



Bob can give this topic the light that needs to be shed on the issue.



W7COX



--

bcollinsmn

Joined: 17 Aug 2008
Posts: 23
Location: St. Paul, MN.

Posted: Sun Nov 16, 2008 12:49 pm Post subject: Re: ARTEX 406 ELT in a 7A

 	  AV8ORJWC wrote: 	
		  Bob, I am hoping that this thread actually expands and becomes a Big

Deal, or at least bigger.



I have felt for some time that the location, mount orientation, ground

plane and attempt at concealing the antenna actually leads to an

ineffective or nearly worthless electronic device.  That premise was

based on the 121.5 variant not the 406 however, because one build might

have mounted it incorrectly, scores follow suit and then  the masses

drink the Kool-Aid.  	




I spent about $900 on this thing. I was awoken by the crash of Steve Fossett, so I want to make sure I get it right.

_________________
Bob Collins
St. Paul, Minn.
RV-7A - Running wires
http://rvbuildershotline.com
Day job: http://minnesota.publicradio.org/collections/special/columns/news_cut/

stein(at)steinair.com
Guest

Posted: Sun Nov 16, 2008 1:02 pm Post subject: ARTEX 406 ELT in a 7A

This is a question I have that is really a question...and I'm not trying to

be fececious....I truly want to know:



Does anyone know of (or ever heard of) any pilot who crashed and died whilst

awaiting a rescue - someone who lived through the crash but died because

rescuers didn't get there?  What I mean is, does any of you know anyone who

crashed, and then waited for CAP or whomever to find them?  Typically I

usually see two results from a crash.  1) Death.  2) Non Death - people live

through the crash and crawl/walk/run away.  Perhaps there are examples, I've

just been trying for years to find any credible for first hand accounts of

where an ELT did or even could have saved a life....  I'm not interested in

hearing hangar stories or "I heard of", but truly credible instances.  They

certainly must be there or we wouldn't have this whole ELT discussion to

begin with. I'm just trying to find such examples.



If you know, please share!



Thanks,

Stein



do not archive



[quote]--

bcollinsmn

Joined: 17 Aug 2008
Posts: 23
Location: St. Paul, MN.

Posted: Sun Nov 16, 2008 1:19 pm Post subject: Re: ARTEX 406 ELT in a 7A

[quote="stein(at)steinair.com"]This is a question I have that is really a question...and I'm not trying to

be fececious....I truly want to know:



Does anyone know of (or ever heard of) any pilot who crashed and died whilst

awaiting a rescue - someone who lived through the crash but died because

rescuers didn't get there? 

 	  Quote: 	
		  -- 	




First let me say, I don't GET putting DO NOT ARCHIVE on that message, Stein. It's a good question that, it seems to me, will be valuable for people who want to follow this in the future.



But the answer to your question is, yes, I'm familiar with one case that happened in my old neck of the woods, Monterey, Massachusetts. A family flew into Great Barrington where there wer eno services, it was night, winter, so they took off again headed toward Westfield and iced up and went down.



Three boys survived. The father survived but died later in the hospital. Three boys survived. The wife and another boy were killed. It took 18 hours to find them.



Here's a link:



http://forum.keypublishing.co.uk/archive/index.php?t-10828.html



Here's one from Canada:



http://www.cbc.ca/canada/north/story/2007/01/08/plane-survivor.html

I'm sure it's not the only case.



I understand your point -- I guess .  Still, if it's a required piece of equipment, why not install it correctly?



For that reason, let's not go into a big debate -- at least in this thread -- on whether ELTS are needed or need to be installed correctly. It's up to each builder. and my choice is it WILL be installed correctly.



Doing some more reading here, it looks to me like I can put a whip antenna topside, 30 inches (at least) forward of the vertical stabilizer. I don't have a problem with antennae in the wind. II presume the skin itself is the ground plane. I do have some concern about whehter there'd be any interference with the GPS antenna but I guess I'll worry about that later.



As far as the mounting is concerned,  I'm starting to wonder if under the turtle deck might make some sense?  Other than that, I'm kinda digging Mike Hoover's installation which he documents here:



http://www.aclog.com/rv-9a/index.php?c=3#909

_________________
Bob Collins
St. Paul, Minn.
RV-7A - Running wires
http://rvbuildershotline.com
Day job: http://minnesota.publicradio.org/collections/special/columns/news_cut/

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sun Nov 16, 2008 1:34 pm Post subject: ARTEX 406 ELT in a 7A

There was a Cherokee 6 that crashed in western Mass in a snowstorm in evening with family on-board, returning from FL. Pilot had been participant in a Piper list. Wife and I think one of the kids died soon after crash. Father survived the night and into morning until he and three surviving kids were found. He died shortly after being rescued. Kids survived.

 http://www.ntsb.gov/recs/letters/2007/A07_51.pdf

 

 NSTB is recommending 406 Mhz ELT's and is using Ron Ferris's accident in

 support of their recommendation

 

 SteinAir, Inc. wrote: [quote]    	  Quote: 	
		  --> RV-List message posted by: "SteinAir, Inc." <stein(at)steinair.com> (stein(at)steinair.com)



This is a question I have that is really a question...and I'm not trying to

be fececious....I truly want to know:



Does anyone know of (or ever heard of) any pilot who crashed and died whilst

awaiting a rescue - someone who lived through the crash but died because

rescuers didn't get there?  What I mean is, does any of you know anyone who

crashed, and then waited for CAP or whomever to find them?  Typically I

usually see two results from a crash.  1) Death.  2) Non Death - people live

through the crash and crawl/walk/run away.  Perhaps there are examples, I've

just been trying for years to find any credible for first hand accounts of

where an ELT did or even could have saved a life....  I'm not interested in

hearing hangar stories or "I heard of", but truly credible instances.  They

certainly must be there or we wouldn't have this whole ELT discussion to

begin with. I'm just trying to find such examples.



If you know, please share!



Thanks,

Stein



do not archive



  	
   

 [b]

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Sun Nov 16, 2008 1:35 pm Post subject: ARTEX 406 ELT in a 7A

--

ronlee(at)pcisys.net
Guest

Posted: Sun Nov 16, 2008 1:52 pm Post subject: ARTEX 406 ELT in a 7A

 	  Quote: 	
		   Does anyone know of (or ever heard of) any pilot who crashed and died 

 whilst

 awaiting a rescue - someone who lived through the crash but died because

 rescuers didn't get there? >

 Thanks,

 Stein


	


Interesting question.  Personally I have ZERO faith in my ELT "saving" me. 

With

121.5 MHz units, a lot of crashes do not activate the ELT.  Is there any 

proof that

406 MHz units are any better?  Not that they are more accurate.  Are they 

more

reliable in activating when they should?



I have a 406 MHz PLB (GPS model) and intend to install an APRS system 

(requires

a ham license) in the future.  Along with avoiding pilot error situations 

that down the

aircraft, I am not worried nor do I intend to get a 406 MHz ELT.



A Spot system offers far better rescue/recovery functionality (similar to 

APRS) than

any ELT in my opinion.



Ron Lee

d-burton(at)comcast.net
Guest

Posted: Sun Nov 16, 2008 3:28 pm Post subject: ARTEX 406 ELT in a 7A

Does anyone know of (or ever heard of) any pilot who crashed and died whilst

awaiting a rescue - someone who lived through the crash but died because

rescuers didn't get there?  



Partner in one of our planes went down trying to cross a local 4000'

mountain pass.  He survived the landing in the woods, organized the contents

of the cockpit and certainly could have activated the ELT if it hadn't

deployed.  He died trying to walk out through the snow.



DaveB

bcollinsmn

Joined: 17 Aug 2008
Posts: 23
Location: St. Paul, MN.

Posted: Sun Nov 16, 2008 3:31 pm Post subject: Re: ARTEX 406 ELT in a 7A

I don't really see any reason for either-ors here. You outfit your plane for whatever you want. If safety is a concern -- and it is for me -- that means traffic avoidance systems, 406 ELTS (yes, they are more accurate than 121.5s), it means an emergency checklist that includes manually activating the ELT before ditching, having the mechanism to use the ELT as a radio, it means SPOT, it means APRS, it means Hooker Harnesses with a crotch strap, it means Oregon Aero seats, it means having a survival kit, it means having a mechanism to break the canop and on and on and on.



Now, then, back to the original question...

_________________
Bob Collins
St. Paul, Minn.
RV-7A - Running wires
http://rvbuildershotline.com
Day job: http://minnesota.publicradio.org/collections/special/columns/news_cut/

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Sun Nov 16, 2008 3:57 pm Post subject: ARTEX 406 ELT in a 7A

Sorry about the previous blank message. I have a friend who is the former

head of the Washington State CAP. I just got an email back from him telling

me that he will tell me the whole story of a CAP member who was lost a few

years ago after crashing in the Cascades in bad weather. He was not

seriously injured but died before the rescuers got to him due to exposure

and apparently also because he had left his survival kit in his car.



OK, I found the report:



Terry



NTSB Identification: ANC95GA048 . 

The docket is stored in the Docket Management System (DMS). Please contact

Records Management Division 

Accident occurred Wednesday, April 12, 1995 in BUMPING LAKE, WA

Probable Cause Approval Date: 9/3/1996

Aircraft: Cessna 182Q, registration: N97843

Injuries: 1 Fatal.

The private pilot, a civil air patrol (CAP) volunteer, was on a CAP flight

for proficiency training and to conduct business. The VFR cross-country

flight was planned over mountainous terrain. The pilot obtained a weather

briefing that included information about icing conditions along the planned

route. During the flight, no communication was received from the pilot other

than activation of his flight plan after departing the airport. The airplane

was reported overdue, but a search was hampered due to IFR conditions and

snow. No transponder code was issued to the airplane, and no discrete radar

data was located in stored radar data to assist in locating the airplane. By

0900 on 4/15/95, analysis of the primary target radar returns helped in

locating the accident airplane. Also, only an intermittent signal was

transmitted from the airplane's emergency locator transmitter (ELT). The

wreckage was located 3 days later, where the airplane had crash landed on

snow covered mountainous terrain. Investigation revealed the pilot initially

survived the accident, but succumbed to hypothermia. He was wearing a flight

suit over dress clothes, a flight jacket, and dress shoes. No survival

equipment was required to be carried in the airplane. The pilot had a

personal survival kit, but had left it in his vehicle at the departure

airport. A note found in the wreckage indicated that the engine lost power.

After recovery, the engine operated normally. The transponder switch was

found in the "standby" position; inspection of the ELT revealed a faulty

tuning crystal. The pilot had received training in survival skills and was a

CAP survival skills instructor. 



The National Transportation Safety Board determines the probable cause(s) of

this accident as follows: 



A loss of engine power for an undetermined reason. Factors relating to the

accident were: lack of suitable terrain for a forced landing in mountains,

low ambient temperatures that contributed to hypothermia, the lack of

survival equipment, an erratic ELT signal due to a faulty tuning crystal,

and the lack of discrete transponder data to assist in the search. 



Full narrative available

Index for Apr1995 | Index of months   






This is a question I have that is really a question...and I'm not trying to

be fececious....I truly want to know:



Does anyone know of (or ever heard of) any pilot who crashed and died whilst

awaiting a rescue - someone who lived through the crash but died because

rescuers didn't get there?  What I mean is, does any of you know anyone who

crashed, and then waited for CAP or whomever to find them?  Typically I

usually see two results from a crash.  1) Death.  2) Non Death - people live

through the crash and crawl/walk/run away.  Perhaps there are examples, I've

just been trying for years to find any credible for first hand accounts of

where an ELT did or even could have saved a life....  I'm not interested in

hearing hangar stories or "I heard of", but truly credible instances.  They

certainly must be there or we wouldn't have this whole ELT discussion to

begin with. I'm just trying to find such examples.



If you know, please share!



Thanks,

Stein

stein(at)steinair.com
Guest

Posted: Sun Nov 16, 2008 3:59 pm Post subject: ARTEX 406 ELT in a 7A

The do not archive was because this was to settle my personal curiosity more

than anything else.  I didn't have anything to add to the technical part of

the discussion, so I guess I just didn't want my weird question filling up

the already bloated archives.  I really wasn't trying to make any sort of

point at all (in either direction), I was simply trying to find out some

data that I hadn't seen/heard/read....I get asked questions like that a lot

of times here in my work, so any additional info at least helps me try to

answer peoples questions.  That's  it, plane and simple - no alterior motive

to start the "should you shouldn't you" debate all over again! 



Cheers,

Stein



do not archive (just to make Bob shake his fist at me) !!!



[quote]--

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Sun Nov 16, 2008 5:40 pm Post subject: ARTEX 406 ELT in a 7A

Stein, can you post here whether you have the equipment to measure and graphically depict the effectiveness of the RF signal transmitted by a properly mounted and functioning 406 device?  Seeing the strength and radiation pattern degradation as a result of a roll bar, a plexiglas canopy, a composite shell or inside an aluminum empennage to save a knot and a half might go a long way for the audience.

  

 Or, if not, can you advise how owners can have the tranmitting pattern graphed for their illumination?

  

 My kool-aid pitcher here in the Pacific NW where rescue can turn to recovery quite quickly is empty.  I interpretted Bob's original post to involve the ARTEX 406 installation instructions for current installation.  Instructions for effective 121.5 signal transmission were lost some 30 years ago.  Steve Fossett's loss just drives the point home.

  

 John Cox

 W7COX

 Aurora, OR



 

  From: owner-rv-list-server(at)matronics.com on behalf of SteinAir, Inc.

Sent: Sun 11/16/2008 12:59 PM

To: rv-list(at)matronics.com

Subject: RE: Re: ARTEX 406 ELT in a 7A

  

--> RV-List message posted by: "SteinAir, Inc." <stein(at)steinair.com>



This is a question I have that is really a question...and I'm not trying to

be fececious....I truly want to know:



Does anyone know of (or ever heard of) any pilot who crashed and died whilst

awaiting a rescue - someone who lived through the crash but died because

rescuers didn't get there?  What I mean is, does any of you know anyone who

crashed, and then waited for CAP or whomever to find them?  Typically I

usually see two results from a crash.  1) Death.  2) Non Death - people live

through the crash and crawl/walk/run away.  Perhaps there are examples, I've

just been trying for years to find any credible for first hand accounts of

where an ELT did or even could have saved a life....  I'm not interested in

hearing hangar stories or "I heard of", but truly credible instances.  They

certainly must be there or we wouldn't have this whole ELT discussion to

begin with. I'm just trying to find such examples.



If you know, please share!



Thanks,

Stein



do not archive





 [quote][b]

Dick Sipp

Joined: 11 Jan 2006
Posts: 215
Location: Hope, MI

Posted: Sun Nov 16, 2008 7:14 pm Post subject: ARTEX 406 ELT in a 7A

I mounted the 406 antenna on the right longeron at  the aft end of the fiberglass top inside the baggage compartment.  It  follows the bend of the top.

  

 My to do list includes an item to try and determine  if I can arrange an actual test activation with the appropriate agencies to  verify reception of the signal.

  

 I report if and when that is done.

  

 Dick Sipp

 N110DV 90 hours

 [quote]   ---

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Mon Nov 17, 2008 1:41 am Post subject: ARTEX 406 ELT in a 7A

John as a fellow HAM, you know the answer, external, vertical polarization with a good ground plane. No one has tested these creative internal ELT antenna installations. It may be fine in a Lancair or Glasair but a all metal RV is not a good canadate for internal antennas. I can tell you the VHF wing tip com antenna's are really piss poor. Any one who has one and is honest will tell you. Some say the wing tip VHF com antenna works. The definition of work is flying 1000' agl towards the airport tower 5 miles infront of you. Forget long distance omni directional communications at max theoretical range of an airborne 5-10 watt VHF transmitter.

   

  One popular hidden ELT antenna location on RV's is laying the antenna horizontal in the vertical/horz stab intersection fairing area, under the vertical stabilizer. It is pretty popular and makes no sense to me from a technical stand point. I DON'T KNOW OF ANY ONE WHO HAS TESTED IT  FORMALLY or INFORMALLY. I personally think its a bad idea. Hidden use but affective range limited.

   

  The other idea is in the wing but that is a LONG coax run unless you put the ELT in the wing tip as well. The wing tip is also really terrible for propagation and practical reasons, like the wing tip rips off. Also access is not great unless you install an access panel.

   

  The Artex 406 has one antenna for both 406/121.5Mhz about the same dimensions as current ELT antennas.

   

  The EBC has two antennas, one short 406Mhz antenna and a seperate 121.5 Mhz antenna. Of course the 406Mhz is very short. 

   

  HERE IS SOME FOOD FOR THOUGHT. The DRAG from one typical (20") ELT antenna is  1/8th mph, 0.125 mph penalty (at 200 mph). Is it worth it to hide antennas?  

   

  If you are talking  about a 406 Mhz only antenna that is a short antenna with negligible drag. When I raced my RV-4 I took off the Com, VOR antennas for about 1/2 mph to 2/3rds mpg gain. I did put the ELT antenna under the bubble canopy.

   

  Some hide antenna for eye appeal. I think it's not worth it but that is a hard sale with many builders I consult with.

   

  I think the best NON standard is mounting the antenna or antennas inside the canopy/cockpit area. The down side is getting a proper ground plane. The old EBC elts had an internal antenna and the unit was always mounted in the cabin. The new EBC uses two remote antennas as I mentioned above.

   

  I did a informal survey of RV accidents that where off field and survivable; many end up on their back, so the belly is not totally a horrible area. That does not follow the common ELT instructions for mounting the ELT  on top of the aircraft.

   

  Of course any thing that does not follow the ELT's instructions violates the FAR / STC approved instructions.

   

  Almost all approved ELT installations call for the following:

   

  - Mount ELT as far aft as possible

  - Antenna'(s) be mounted close by, no excessive long coaxial run

  - Mount the antenna externally.

  - Provide maintence access & access after accident

   

  So the approved ideal location is ELT in the tail cone far aft with the antenna'(s) mounted directly above on the back top, just forward of Vert stabilizer.

   

  The old transmitter was only 100mw and now the new 406 ELT's have 5 watt burst, so that is better regardless of antenna. Still of the antenna is shielded from the satellites than you are invisible even with 5 watts. We also still  need 121.5 Mhz and 100mw for local DF steer to find us. How far can can 100mw get out with an antenna buried inside of metal structure? I think you are talking feet not miles in range.  

   

  I just can't stand to see such a violation of good antenna installation practices for the sake of looks and a tenth of a mph. 

   

  Cheers George

   

   

   

  *************************************************************************************************

Subject: RE: Re: ARTEX 406 ELT in a 7A

From: "John Cox" <johnwcox(at)pacificnw.com>

Bob, I am hoping that this thread actually expands and becomes a Big

Deal, or  at least bigger.



I have felt for some time that the location, mount orientation, ground

plane and attempt at concealing the antenna actually leads to an

ineffective or nearly worthless electronic device.  That premise was

based on the 121.5 variant not the 406 however, because one build might

have mounted it incorrectly, scores follow suit and then  the masses

drink the Kool-Aid.  I have always concluded the function might not be

important, only its presence for the DAR signoff.



I have remained curious how many rescues rather than recoveries "after

the fact" are attributed to a properly functioning signal and a

responsible response by the parties that monitor the frequency (either

121.5 or 406.



As a ham (amateur) radio license holder this pursuit of concealing the

antenna has always been fascinating.  Do any of the readers have signal

propagation graphs on signal strength radiating from inside the  tin

 can?



John Cox

Aurora, OR

             [quote][b]

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Nov 17, 2008 5:18 am Post subject: ARTEX 406 ELT in a 7A

Well just some random musings. I know of TC aircraft with the ELT 

antenna bent back under fiberglass ventral fin in otherwise all metal 

aircraft..but don't know whether any feds cared about it. I know that my 

121 ELT activated on its own in my all metal hangar, and was satellite 

detected. Only the weird propagation pattern made it a little difficult 

to ascertain it was coming from my hangar and not an ajacent row. So, 

not so sure how critical this is, especially at 406 where your radiating 

element is approx 1/4 the length of 121 element. Ever look at a police 

supervisor car? They often have 5 or 6 UHF antennas around the roof and 

trunk, not very far apart. Wonder what issues they have.



gmcjetpilot(at)yahoo.com wrote:

 	  Quote: 	
		   John as a fellow HAM, you know the answer, external, vertical 

 polarization with a good ground plane. No one has tested these 

 creative internal ELT antenna installations. It may be fine in a 

 Lancair or Glasair but a all metal RV is not a good canadate for 

 internal antennas. I can tell you the VHF wing tip com antenna's are 

 really piss poor. Any one who has one and is honest will tell you. 

 Some say the wing tip VHF com antenna works. The definition of work is 

 flying 1000' agl towards the airport tower 5 miles infront of you. 

 Forget long distance omni directional communications at max 

 theoretical range of an airborne 5-10 watt VHF transmitter.

  

 One popular hidden ELT antenna location on RV's is laying the antenna 

 horizontal in the vertical/horz stab intersection fairing area, under 

 the vertical stabilizer. It is pretty popular and makes no sense to me 

 from a technical stand point. I DON'T KNOW OF ANY ONE WHO HAS TESTED 

 IT FORMALLY or INFORMALLY. I personally think its a bad idea. Hidden 

 use but affective range limited.

  

 The other idea is in the wing but that is a LONG coax run unless you 

 put the ELT in the wing tip as well. The wing tip is also really 

 terrible for propagation and practical reasons, like the wing tip rips 

 off. Also access is not great unless you install an access panel.

  

 The Artex 406 has one antenna for both 406/121.5Mhz about the same 

 dimensions as current ELT antennas.

  

 The EBC has two antennas, one short 406Mhz antenna and a 

 seperate 121.5 Mhz antenna. Of course the 406Mhz is very short.

  

 HERE IS SOME FOOD FOR THOUGHT. The DRAG from one typical (20") ELT 

 antenna is  1/8th mph, 0.125 mph penalty (at 200 mph). Is it worth it 

 to hide antennas? 

  

 If you are talking about a 406 Mhz only antenna that is a short 

 antenna with negligible drag. When I raced my RV-4 I took off the Com, 

 VOR antennas for about 1/2 mph to 2/3rds mpg gain. I did put the ELT 

 antenna under the bubble canopy.

  

 Some hide antenna for eye appeal. I think it's not worth it but that 

 is a hard sale with many builders I consult with.

  

 I think the best NON standard is mounting the antenna or antennas 

 inside the canopy/cockpit area. The down side is getting a proper 

 ground plane. The old EBC elts had an internal antenna and the unit 

 was always mounted in the cabin. The new EBC uses two remote antennas 

 as I mentioned above.

  

 I did a informal survey of RV accidents that where off field and 

 survivable; many end up on their back, so the belly is not totally a 

 horrible area. That does not follow the common ELT instructions for 

 mounting the ELT on top of the aircraft.

  

 Of course any thing that does not follow the ELT's 

 instructions violates the FAR / STC approved instructions.

  

 Almost all approved ELT installations call for the following:

  

 - Mount ELT as far aft as possible

 - Antenna'(s) be mounted close by, no excessive long coaxial run

 - Mount the antenna externally.

 - Provide maintence access & access after accident

  

 So the approved ideal location is ELT in the tail cone far aft with 

 the antenna'(s) mounted directly above on the back top, just forward 

 of Vert stabilizer.

  

 The old transmitter was only 100mw and now the new 406 ELT's have 5 

 watt burst, so that is better regardless of antenna. Still of the 

 antenna is shielded from the satellites than you are invisible even 

 with 5 watts. We also still need 121.5 Mhz and 100mw for local DF 

 steer to find us. How far can can 100mw get out with an antenna buried 

 inside of metal structure? I think you are talking feet not miles in 

 range.  

  

 I just can't stand to see such a violation of good antenna 

 installation practices for the sake of looks and a tenth of a mph. 

  

 Cheers George

  

  

  

 *************************************************************************************************

 Subject: RE: Re: ARTEX 406 ELT in a 7A

 From: "John Cox" <johnwcox(at)pacificnw.com 

 <http://us.f431.mail.yahoo.com/ym/Compose?To=johnwcox(at)pacificnw.com&YY=17621&y5beta=yes&y5beta=yes&order=down&sort=date&pos=0&view=a&head=b>>

 Bob, I am hoping that this thread actually expands and becomes a Big

 Deal, or at least bigger.



 I have felt for some time that the location, mount orientation, ground

 plane and attempt at concealing the antenna actually leads to an

 ineffective or nearly worthless electronic device.  That premise was

 based on the 121.5 variant not the 406 however, because one build might

 have mounted it incorrectly, scores follow suit and then  the masses

 drink the Kool-Aid.  I have always concluded the function might not be

 important, only its presence for the DAR signoff.



 I have remained curious how many rescues rather than recoveries "after

 the fact" are attributed to a properly functioning signal and a

 responsible response by the parties that monitor the frequency (either

 121.5 or 406.



 As a ham (amateur) radio license holder this pursuit of concealing the

 antenna has always been fascinating.  Do any of the readers have signal

 propagation graphs on signal strength radiating from inside the tin

 can?



 John Cox

 Aurora, OR



 *



 *

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

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