Triplexer for Nav/GS & Com?

[hish747]

Hi All,
I have the AV-571 Triplexer in the first picture installed in my Piper Cherokee 140. The newer AV-571 now omits the Com label and only mentions Nav & GS as shown in the second picture.

Does anyone know why these units changed? Did they find out it doesn't work after all? Is it even proper to run a Nav, Com and GS off the same antenna? I'm trying to get a second com installed and am trying to figure out if I need another antenna installed or if I can connect into the available com rec port on the unit. I assume that if it works, it will mean weaker signals for everything, right?

What about sending? Would sending require another antenna even if tapping into the triplexer works for receiving?

Thanks for any thoughts.
Hish

 

[Witmo]

It's funny that the older one says Nav Com but doesn't include the Com frequencies as it just lists 108-118 which are nav, but the newer one that omits "Com" does include the com freqs 108-(118)-136. I'd definitely go with separate comm antennae for each comm transceiver for the best performance.

 

[Ravioli]

I think it is customary to have a 1 comm antenna for each radio but the nav radios can share a third antenna.

Com's are usually vertically oriented and Nav's are more horizontally oriented.

Your shop can tell you more, since your installing in a certificated airplane.

 

[Piloto]

I have one on my Mooney and it works really well. It was wrong to include COM on the labeling since these are strictly for receiving only.
José

 

[weirdjim]

I have one on my Mooney and it works really well. It was wrong to include COM on the labeling since these are strictly for receiving only.
José

You are correct, Jose. It is theoretically possible but practically IMpossible to multiplex two COM transceivers onto a single antenna.

Jim

 

[hish747]

Thanks for all the responses. So should it not be used even to join the single com?

 

[bnt83]

Hi All,
I have the AV-571 Triplexer in the first picture installed in my Piper Cherokee 140. The newer AV-571 now omits the Com label and only mentions Nav & GS as shown in the second picture

You NEED an additional comm antenna. I have never seen ANY multi VHF comm equipped aircraft share a single antenna. I bet you can't even find VHF comm radio manufacturer that suggests it's an option. Each comm radio gets a dedicated antenna. Read the manuals.

 

[hish747]

You NEED an additional comm antenna.

I'm going to be installing an additional antenna when I get the second radio. But the radio that was installed when I bought the plane was connected through this triplexer and has been working reliably. The question is whether there's an electrical reason why this needs to be changed. Thanks again.

 

[bnt83]

Looks to me like that connects two nav receivers and a glide slope receiver to one antenna. If true, it doesn't have anything to do with voice VHF comm transceiver. What readios are in the airplane?

 

[hish747]

Just one radio installed, a King KX 155. But, I'd like to get a second Com radio.