ELT Antennae Mounting

[Tucky Bourbon]

Hi all, I recently mounted my ELT antennae in my RV8. I didn't like the location/antennae mounted in the empennage so I wanted to try to mount mine in the cockpit above the rear seater's shoulder. I got it all installed and was a bit proud until I thought about the p-clamps themselves. Will the metal in the p-clamps interfere with the antennae performance? I already have some nylon ones on order and I plan to do some testing but I want to poll the brains out there. Am I over thinking this or have I degraded the performance of the antennae by wrapping it in loops of metal?

Appreciate any insight for a first-time builder,

Chris

 

[Webb]

Overthinking. The flat piece of aluminum the clamps are mounted on will have more influence on the radiation pattern than the cushion clamps.

Of course you could always turn it on and see if you are located………

 

[Carl Froehlich]

I don’t recommend mounting it in the cabin like this, but if you really want to replace the adel clamps with stand off insulators that provide at least 1” from any metal. You can make them out of plastic hangars, wood dowels and such.

The down side is the rear passenger will likely break them off from time to time.

Carl

 

[Webb]

I suspect there are a few others out there that mounted this way.

 

[RV7 To Go]

I found no good by the book places to mount the ELT antenna on an 8. Another builder at our field mounted his the same way but used plastic clips instead of the metal ones. Not sure it matters. I bought the Artex with the short 15" antenna and mounted it in the same location. The short antenna clears the canopy without a bend. Shouldn't be an issue for the passenger but we'll see.

 

[bjdecker]

Hi all, I recently mounted my ELT antennae in my RV8. I didn't like the location/antennae mounted in the empennage so I wanted to try to mount mine in the cockpit above the rear seater's shoulder. I got it all installed and was a bit proud until I thought about the p-clamps themselves. Will the metal in the p-clamps interfere with the antennae performance? I already have some nylon ones on order and I plan to do some testing but I want to poll the brains out there. Am I over thinking this or have I degraded the performance of the antennae by wrapping it in loops of metal?

Appreciate any insight for a first-time builder,

Chris

The clamps aren't the problem. The big metal bulkhead will interfere with the antenna's operation. At a minimum, please use a VNA or similar to verify the antenna's characteristics at 121.5MHz and 406MHz -- still 50ohms? VSWR still 2.5:1 or lower? S11?

Here's a couple of youtube videos to watch -- ignore the "Army Health Film" feel.. it's good information.

IMHO This is one of those "endless debates" -- What happens after what happens happens? Does the antenna break off in the crash? Does the antenna cable get cut by a bulkhead during the crash? Should I mount the antenna horizontally or vertically? etc. etc.