antenna guru's

gereed75 · #1 08-16-2011, 09:46 PM

Looking for a good place to mount my new 406 ELT antenna that has a good ground plane ---

OK, I know this must be a bad idea, or everyone would be doing it.... but please tell me why it would not be possible to hook a 406 ELT into the comm antenna mounted on the turtle deck using a splitter?????

It appears to be the right length, and it has a good ground plane.

Why not??? Thanks

SkywayCaptain · #2 08-17-2011, 07:45 AM

A couple reasons this will not work well are...

1. The com antenna is not tuned for the frequencies that your 406 ELT operates at. This means there will be a large impedance mismatch between the antenna and the coax. Most of the ELT's transmit signal will be reflected back to the ELT and not transmitted. This could possibly damage the ELT in addition to having an extremely weak output signal.

2. Depending on what type of "splitter" you used, the ELT transmit signal could very possibly damage the com radio by sending a much stronger signal than the com radio was designed to receive.

3. You will not meet the TSO requirements for the ELT install.

fmarino1976 · #3 08-17-2011, 08:48 AM

I think that besides the reasons given above, the first time you transmit on your com, it will most likely damage the ELT. Remember that the Com puts out several watts of RF. If you pipe this into the ELT that was not designed to receive any signals, you might not like the results.

gereed75 · #4 08-17-2011, 09:36 AM

Kinda figured that those would be the reasons. never thought of the TSO issue.

So next question - what is the minimal ground plane size that such an antenna needs (the supplied ant is about 20" length) and or what are the ramifications of running the antenna with a small or non -exsistent ground plane (like many do with an under the tail fairing installation)????

Thanks