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A new idea for ELT antenna placement

Some Grumman Yankees actually did something similar, but it's more like a 2" spacing between the radiating element and the V-stab.

I'm not sure what the radiation pattern looks like. If I had to guess, I'd say cardioid.

You also run into issues with TSOs and required impedance matching networks. Closer spacings would likely mean significantly reduced efficiency.
 
Careful mounting it too close to the VS on the top of the fuselage. I know of one -8 that has done this and has nice scratches on both sides of the VS where it has blown back in flight and whipped the VS on both sides.
 
How about a retractable antenna, when the canopy closes the antenna goes up :eek:

c3-corvette-power-antenna.jpg
 
Why can't it be mounted on the canopy skirt at the very aft end and grounded to the canopy frame? It's vertical, semi-protected by roll bar and vert stab. Wiring run? Yea, a potential challenge, but someone here can solve that.
Clay Cook
 
A composite V-stab might be the simplest solution electrically and mechanically if you are trying to achieve strict compliance with TSOs.
 
N941WR said:
Careful mounting it too close to the VS on the top of the fuselage. I know of one -8 that has done this and has nice scratches on both sides of the VS where it has blown back in flight and whipped the VS on both sides.
Click to expand...

I should probably add that the Grumman design supported the antenna with spacers between it and the V-stab.

1971_Grumman_AA-1ALR.jpg
 
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Thought I would show how it turned out. Still need to make and rivet in the skin doubler. Hopefully it will be stiff enough not to whip back and hit the stab.

Canopy closed:

IMG_5981.JPG


Canopy open:

IMG_5979.JPG


Will put some foam in under the skirt when I glass it up, will need to cut a notch in the fairing as well. The forward sweep does look a bit odd, but probably about as good a radiation pattern as anybody gets on a 8. Hopefully never need to find out.
 
revisiting antenna placement on the RV-8

With the recent announcement about Ameri-King raising the possibility that it will be followed by an AD dictating removal from service of existing equipment, I thought I would explore what my ELT options are. Looks like pretty much the 406/121.5 ELTs are all that are available. ACK being the most reasonable.

But that renews the antenna dilemma.

Question for everyone: Does the requirement from the ACK installation manual that: "The antenna must be mounted
within 30 degrees of vertical, when the aircraft is in normal flight attitude" really preclude mounting on the bottom? Isn't it still "vertical" even if it is upside down?

In previous threads many have observed that if I'm upside down, I probably need help more than if I am right-side up, and I would want my antenna performing best then. But that is still rationalization when it is required to comply with the TSO. But being oriented vertical, on the belly, doesn't that meet the letter of the requirement?
 
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ELT Antenna Placement

Here are three photos of how I located my ELT Antenna under the canopy of my RV8.

I fabricated a small bracket that mounts between the members of the mid cabin cross bar.


The bracket is angled slightly as can be seen in this photo. While it does momentarily touch the front bow of the canopy as it's closed it does not contact the inside of the canopy at any point so there is no danger of scratching the surface.


The rear passenger when entering the aircraft does need to be careful not get hung up on it but that's the only drawback I see.
 
Can you post a pic

Hi Gary,

Your installation sounds like a good idea. Can you post a pic so we can see it?

Thanks for your real world feedback!
 
I was going to mount mine similar to Burke's but maybe put the bracket in the center of the back of the pilot's seat. Any reason that's a bad idea other than the passenger having to negotiate around it getting in and out?
 
I know the aesthetics are not great but a small doubler plate and a simple installation that is out of the way and meets the ACK installation instructions meets my needs:



I've hardly thought about this antenna since installed and have had no issues with it at all.
 
Antenna wiring

I was planning on putting the antenna under the empenage fairing. However, the new 406 antenna's are too long to mount on the aft bulkhead. So, now thinking about installing on the passenger armrest. My question is how to get the antenna coax from inside the cockpit back to the ELT unit without penetrating a bulkhead?:confused:
 
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