The remaining cables to be routed under the rear seats before the floors are permanently installed are the COM Antenna cables.
I had previously riveted doublers to the bottom skin in the area of the second most outboard bay under the rear seats on each side of the cabin, so now it was a matter of running a coax cable from there to the cabin side and forward towards the panel area.
I purchased about 75ft of RG400 coax cable which I estimate should be enough for all the coax cable runs needed for my setup, and cut two 10ft lengths for the COM Antenna runs. Prior to running the coax cables, I crimped female BNC connectors onto one end of each cable. This was relatively straightforward using a suitable crimper and taking care to keep the shield and conductor separated.
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| Female BNC connectors crimped onto one end of each RG400 cable |
Each COM Antenna cable passes through a hole punched in the second most outboard rear seat rib, and then up through the rear seat floor where it then continues forward through lightning holes in the Bulkhead Side Channel and Seat Rib Intercostal.
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| RG400 cable runs through the rear seat rib and will then pass upwards through the floor once that is in place |
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| Same setup on the right side of the cabin for the COM2 Antenna Cable |
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| Cable exits the bottom skin through the doubler. Access panels in the rear seat floors will later be used to secure the COM Antenna to the skin/doubler |
To support the RG400 cable through the seat rib intercostals, I 3D printed a cable bracket sized for the diameter of the RG400 cable. This gets riveted to the Seat Rib Intercostal web next to the lightning hole through which the cable passes.
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| I also fabricated a bracket from a piece of angle so that I could use an adel clamp to secure the RG400 as it passed through the bulkhead side channel. I wanted to use an adel clamp here to prevent the cable from moving and provide some strain relief where the cable connects to the antenna |
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| With the rear seat floors in place the COM Antenna cable passes nicely through grommets up through the seat floor (left) |
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| Access panel in the rear seat floor giving full access to the antenna cable where it exits through the bottom skin |
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| COM Antenna cable passing under and up through the right rear seat floor. The cable was wrapped in protective sleeve where it passes through the grommet. |
Dates: April 7 - May 1 2026
