So here's the mod. I'm posting this primarily for feedback and to pay it forward to anyone else who may want to attempt this. It is an easy mod. The hardest part was removing the gimbal and connecting the uf.l. connectors and that was more tedious than it was difficult.
My motivation here was threefold:
1) replace the stock directional plate 2.4 GHz antennae with something better (hopefully).
2) allow easy replacement of various rp-sma antennae to experiment with different types.
3) in the undesired event of blunt trauma causing the gimbal to once again separate from the mother ship, the repairs should be limited to an inexpensive replacement of uf.l. to rp-sma cables (I have a spare set).
Right, so here are the steps.
1) Remove the gimbal from the bird. I didn't get any pics of this, but it is well documented and you can see videos on you toob. To get to the uf.l. connectors it will be necessary to remove those two little plates. There are two screws holding each one on as in this photo:
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2) once the uf.l. to rp-sma cables are connected to the gimbal we can focus on drilling a couple holes in the legs. I chose to use the legs which do not have the 5.8G antennae in them. One leg is empty and the other has the compass cable in it. Be sure this cable is out of the way before you drill! In the pic below you can see the location I've used. It's about 1/2" down and about 3/8" from the left side. Make sure you drill low enough that you do not drill into the top 1/8" which is used to hold the legs to the body. Also in the photo you can see the bits I am using here. These are brad points and are ideal for drilling into plastic. The tip will keep you centered on your mark and it will tend to cut the hole clean.
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3) I drilled a 1/8" pilot hole first and then finished with a 1/4" bit.
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Notice how I've kept the compass wire out of the way!
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4) Now just insert the rp-sma connector with the washers and tighten her up.
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5) A view from behind showing that the compass wire is safe and sound.
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6) Attach the antenna. For now I have left the wires outside. I may look at routing these through the shell for better protection, but for now I like the clean look.
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7) These are 6dbi antennae and are 6" long so they can't hang straight down. Here is how I orient them for flight. I would appreciate hearing from anyone with RF experience if there is a better orientation.
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Next will be the DBS mod. If that is half as successful as what I have read on here I may try smaller 3dbi antennae. Feedback appreciated in advance.