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  #1  
Old 05-21-2017, 11:11 PM
cdeerinck's Avatar
cdeerinck cdeerinck is offline
 
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Location: San Marcos, CA
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Question ACK-04 in an RV-8

I reached out to Vans to get ideas on where to mount an ELT antenna in the RV-8, given the severe lack of choices. They replied that many owners put it under the tail fiberglass cowling.

I understand that it can't be within 30 degrees of vertical in that location, as called out in its manual, but I can't for the life of me figure out how to mount it or give it any ground plane for the antenna.

I have seen posts of people putting it in the cockpit, and that won't work for me, but I'm open to other ideas.

Can anyone share a picture, URL, or description on how they mounted theirs in that location?
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  #2  
Old 05-22-2017, 12:33 AM
rv8ch rv8ch is offline
 
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Default ELT antenna location in RV-8

Here is what I did:

http://www.rv8.ch/elt-antenna-placement/

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  #3  
Old 05-22-2017, 01:00 AM
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cdeerinck cdeerinck is offline
 
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Default

Quote:
Originally Posted by rv8ch View Post
Here is what I did:
Where did you get that antenna? The one that came with the ACK-04 is about 3-4 times that long.

You can see it here.
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  #4  
Old 05-22-2017, 01:28 AM
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cdeerinck cdeerinck is offline
 
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Default Maybe this?

I think maybe I found my answer here: http://www.vansairforce.com/communit...d.php?t=142810

But I would love to know if N130WN ever got it working right.
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  #5  
Old 05-22-2017, 02:52 AM
rv8ch rv8ch is offline
 
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Default Rubber ducky antenna

http://www.vansairforce.com/communit...read.php?t=451
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  #6  
Old 05-22-2017, 07:47 AM
aerovin aerovin is offline
 
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Default

This has worked just fine and complies with the ACK installation manual and uses the ACK antenna.



I added a doubler plate and restricted the aft travel of the canopy by about 3 inches. Maybe not as pretty but works.
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  #7  
Old 05-22-2017, 08:16 AM
greghughespdx greghughespdx is offline
 
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Quote:
Originally Posted by rv8ch View Post
Will that with a 406 ELT as well?
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  #8  
Old 05-22-2017, 01:57 PM
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cdeerinck cdeerinck is offline
 
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Default This is insanity

The specs as called out in the manual are crazy. They want a minimum 24" diameter grounding plane, with 48" being optimal. The book also says you can't substitute the antenna unless it complies with this:
VSWR @ 121.5 MHz <= 2.5:1
VSWR @ 406 MHz <= 1.5:1

Does anyone know of any antennas that meet that requirement, hopefully in a short whip, or a blade?

I see builders who are no doubt desperate to get their plane finished pushing it to the limits of where it won't throw an error code but probably will never reach the satellite. Many have grounding planes of a few inches. Some have installed them in the cockpit and those are not only inconvenient but don't have a grounding plane either. The closest was the last post (which the poster admits is not pretty), but it is still between the rudder and elevator, so will block 3/4 directionality. Please note, I am not criticizing any of them.

One person who swapped with another antenna in a parallel thread said "It broadcasts on Comm frequencies... ...so it should be ok", which a 406mhz is not.

ACK makes a blade, but it costs $1k (seriously!?!), but you are prohibited from putting it on the bottom.

My biggest concern is going upside down in a tail dragger, so why is the bottom bad? If I am crashing in the sticks, and end up not being able to walk away or call on the radio, or a cell, isn't it much more likely that I will be upside down?

The Search & Rescue and Civil Air Patrol guys always say to follow the book, and not to put it near the tail feathers, as it blocks transmission. And the mothership says to do what everyone else says not to do.

I understand this needs to reach a satellite (in space obviously), so I can't see a weak signal doing that, and almost everyone tests only the 121.5 frequency (even the book says not to test the satellite part).

<Ok, End RANT>

So are we all just closing our eyes and hoping for the best? I can see the accident reports saying "ELT installed not in accordance with recommended practices".

I thought maybe on top of the rudder, but there is no viable ground plane, and that will be the first thing to go if the plane flips.

Has anyone tried a mod to the tail fiberglass, to locate the antenna right in front of the rudder by an inch of so?
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  #9  
Old 05-22-2017, 06:11 PM
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RV8JD RV8JD is offline
 
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Default RAMI AV-100 ELT Antenna

Quote:
Originally Posted by cdeerinck View Post
The specs as called out in the manual are crazy. They want a minimum 24" diameter grounding plane, with 48" being optimal. The book also says you can't substitute the antenna unless it complies with this:
VSWR @ 121.5 MHz <= 2.5:1
VSWR @ 406 MHz <= 1.5:1

Does anyone know of any antennas that meet that requirement, hopefully in a short whip, or a blade?
I was looking at the RAMI AV-100 ELT antenna. 13.75" long, $210. It eliminates the long plastic part of the ACK antenna. And seems to meet the VSWR requirements:
VSWR: 121.5 MHz 2.0:1 Maximum
406 MHz 1.5:1 Maximum
http://www.aircraftspruce.com/catalo...ickkey=4224999

Specs:

http://www.aircraftspruce.com/catalo...av100specs.pdf
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Last edited by RV8JD : 05-22-2017 at 06:13 PM.
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  #10  
Old 05-22-2017, 06:19 PM
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BruceEicher BruceEicher is online now
 
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Default

Why is it so restrictive? Liability? Does a personal ELT have such an antenna with a big ground plane, no. Mine is on the GIB's armrest, curved around the seat back, like many others I believe.
My plan is not to crash...
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