Transponder & ADS-B

Time: 4 Hours

I installed the transponder and ADS-B units today that arrived from Aircraft Spruce. I had done most of the legwork for this install several years ago by installing the Dynon cables as well as the antennas. I had also created a shelf that I installed both COM radios that would also hold the transponder and the ADS-B units. For those of you that are reading this and unfamiliar, the transponder is the unit that sends a discreet signal to air traffic control for their radar identification. The ADS-B Is a fairly new required system that provides much more detail to air traffic control about where your aircraft is, its movement and information. It also has the ability to receive more information, such as weather radar and airport weather reports.

To start this project I need to remove the shelf which sits just behind the aft baggage compartment.Before I did that I crawled back and laid out where the transponder and ADS-B would go so that the wires and antenna cable’s would not interfere with items like the rudder cables or elevator push/pull tube.

With those spots marked I could remove the shelf and take it to the workbench to install nutplates to hold both units down.I decided long ago to use net plates for all of these so that would make it easy to remove with just a screwdriver for future repairs and maintenance.

A test fit looks great!

I then returned the shelf back to its position and bolted it down with the 4 AN-3 bolts. I connected the Dynon working harnesses to each of the four units. I connected the COM antennae cables to the units. Now that the shop was in place and all the units were secured I could measure for the antenna cables for the transponder and ADS-B units. These require RG-400 coax cable like the COM radios. has helpful videos online including how to crimp BNC & TNC type connectors you RG-400 coax cable. I did a review since it’s been some time since I did the COM cables. It’s not hard especially if you have the correct crimper. I made the transponder cable the correct length and only had to add a TNC end on the transponder side as I had the antennae side done when I installed the antennae.

I planned on doing the ADS-B cable from the remaining length cut from the transponder cable which means I would need two BNC connectors. One for each end…I only had one remaining in my stock. So I could finish that cable and will get to it next week when it arrives from Aircraft Spruce. Here is what the shelf with the units in place looks like in the tail. I just need to add the antennae cable next week.

I could still finish up the computer side of the install without that cable installed. Dynon makes it pretty simple with step by step instructions. I did have to go back into my notes to remember which serial pins I used for each of the units as you need to tell the SkyView system what’s connected to what. Once that’s done there are just a few settings you need to add like your tail number, aircraft dimensions etc. Once that’s done it was time to test everything and see how it looked on screen. I won’t be able to check the ADS-B until I get the cable installed and I may not get a signal on the ground even with that. So inflight testing will be required then. Here are a few screen grabs of the Dynon. You can see several cool things like the pink “cross hairs” that’s my flight director that having two autopilot Serbia allows for. You can also see the green transponder code of 1200 at the very top of the screen in the first screen grab. The second screen grab the transponder is in the standby mode and the autopilot is engaged, the flight director bars get balls added to the end of the flight director bars to indicate that the autopilot is engaged.

I love build days like this and you get to see some cool stuff come to life. I can’t wait to use all this cool tech in the air!

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