I started off with the Garmin GTX 330ES transponder. It did what it was supposed to do, mostly staring back at me with with a "1200". It also provided TIS-B to my GTN 650 and my GRT HXr EFIS.
What it didn't do was provide FIS-B to my GTN 650, although I have the SkyRadar DX providing that to my HXr screens. But, wouldn't it be nice to use the 650 for FIS-B info too? Enter my new transponder, the GTX 345.
What it didn't do was provide FIS-B to my GTN 650, although I have the SkyRadar DX providing that to my HXr screens. But, wouldn't it be nice to use the 650 for FIS-B info too? Enter my new transponder, the GTX 345.
Functionally, the user experience between the two is essentially identical. The 345 has a white display rather than the green display of the 330ES. It can stream TIS-B and FIS-B info via its Bluetooth transceiver (to a limited group of Garmin-only apps, all but one of which costs money) and includes an integrated AHRS (available only to apps that must be purchased). It's also 1.01" less in length and 0.03" shorter than the 330, thus requiring a tray swap. And cruelly, it has a different pinout scheme than the 330 family. So it's not a plug-and-play replacement.
Here's the new wiring map I made for the 345. It requires an ethernet connection to the 650 (what Garmin calls HSDB, or high speed data bus), something the 330 family didn't offer. I also wanted to connect an additional RS-422 line to my left HXr EFIS and a RS-232 line to my right HXr EFIS. This is for both redundancy and testing to see if the 345 can send full TIS-B and FIS-B info to the EFISs.
Just for giggles, here's what the wiring change would look like if I were to rewire my current 330 harness for the 345. As you can see, it's a mess.
So rather than risk breaking things, I decided to fashion a little dongle that rewires things for me. I had to buy some parts (62-pin female d-sub receptacle, hood and female HD pins) and keep the dongle as short as possible so as not to cause undue strain on the existing wiring. I also needed to pull new wires for the ethernet connection to the 650 and through to the EFISs to support the additional RS-422 and -232 connections previously described. Here's the dongle.
Here's the 345's new tray in place. Since it's 1.01" shorter than the 330ES' try, I had to drill new holes for the forward screws. Thus, I could not attach the tray to the forward pair of tray supports angles I put in back in 2016 (bottom of this post).
Here's the 345 in place (EFIS was off, so no SAT and DALT info available) and my happy 650 with FIS-B info.
