The buoy was actually the most difficult part of this project. I needed to come up with a stable, waterproof, floating unit to hold the transmitting unit. I could find nothing useful on line that I could purchase and adapt that would do the trick. There were a few projects that looked promising, but they used 3D printed components. I didn't have a 3D printer, nor the knowledge to design an appropriate model - so that was out of the picture. Eventually I decided to use ABS or PVC. They were readily available and cheap. You didn't need a lot of tools to work with it. A hacksaw pretty well covered it.

I wanted to use a small sealed battery. Ideally I wanted to used a small lead-acid battery for a power supply. I figured it would provide a lot of power - for at least 12 to 24 hours. Unfortunately I couldn't find any to fit into 3" ABS pipe. They WOULD fit nicely into a 4" ABS pipe - but they don't make the pipe in that size. The only alternative as to go to 6" PVC (white) pipe. The problem was it was hard (not impossible) to source and expensive. It also didn't have a lot of parts (like a cleanout Plug). I did purchase some, but it proved to be unwieldy to work with. So I had to abandon it and go back to working with 3" ABS(black) pipe. I found my transmitter unit - sealed in 2" ABS pipe fit nicely. I had to revert to Li-Ion battery pack - which would not provide as much power as I wanted (about 6 hours - if used carefully). A mayonaise jar full of sand provide ballast.

For stabilizing I created a ring made out of pex plumbing parts and a kid's swimming noodle.

Supplies

14 inch piece of 3 inch ABS(black) pipe.
(2) Charlotte Pipe 3" Spigot FPT Pipe adapter $ 7.13
(2) Charlotte pipe 3" pipe cleanout plug $ 5.18
(2)RP-SMA male plue to RP SMA female 4-hole panel mount RG 316 pigtail $ 5.04
Waterproof car plug connector with wire 18WG terminal - 4 connectors
(1) Stainless steel ring eye-bolt
3 inch Oatley ABS closet Flange with plastic ring $ 4.00
5 pack 1/2inch by 1/2 inch pex brass tees $ 8.54
6 feet of 1/2 inch pex pipe
Hollow kid's swimming noodle $ 2.00
ABS glue
Marine grade epoxy glue
zip ties

Step 1: The Buoy Casing

I wanted to make the buoy as "small" as possible so it would be easy to move in concert with the crab trap. Once I was limited to three inch ABS determining the length became rather easy. I needed about six inches for each of the elements: The transmitter unit in the sealed 2:ABS, the battery pack, and the mayonaise jar that would be filled with sand for ballast. The ideal length was about 18 inches.

Step 2: The Buoy Casing - the Bottom End

After determining the length, spigot FPT Pipe adapters were glued on both ends of the pipe. On the bottom end a cleanout plug with a stainless steel ring eyebolt would be inserted (Not Shown) in the "well" end of the plug. After tightening the bolt with washers on either end, I filled the "well" with liquid epoxy to ensure a water tight connection. I placed silicon sealant on the outside of the bolt. This is a good time to double check the plug has a rubber gasket just above the threads. (One I bought was missing this - and it leaked).

Step 3: The Buoy Casing - the Top End.

The top end is a bit more complicated. The top cap of the two inch ABS pipe holding the transmitting unit was epoxied onto the inside of the cleanout plug. Take care to make sure the cap is centered. Two holes were drilled through the cap and plug out to accommodate the antenna mounts.to all the two RP-SMA male plug to RP SMA Female 4-hold panel mounts to be placed on the Cleanout plug.

A hole was drilled through the center well and cap (the middle of the plug) to accommodate the harness that connects the transmitting unit to the crab trap.

the water proof connector is placed through the hole and then the four wires from the small connector are attached to the waterproof connector:

red to red

black to black

Green to green

brown to blue

Step 4: The Buoy Casing - Continued

After everything has been placed through appropriate holes. the antenna mounts were epoxied onto the outside of the plug with marine grade epoxy glue. Epoxy glue was also placed around the hole and cable to the connector. Similar to the bottom plug I put in about an eighth of inch of epoxy resin in the bottom of the cap (don't use too much or the cap won't fit on the pipe).

Step 5: The Stabilization Ring

Building the ring was actually one of the most difficult steps. To begin with I had no real plan in advance and I wanted to use whatever parts I had lying around the workshop. One of the hardest things to source was the ring that would slip over the 3 inch ABS pipe and allow me to attach spokes out to the ring. I finally settled on a Closet flange with plastic ring. This is a unit that's usually used to terminate the pipe on the floor of a bathroom. It's designed to connect to the toilet. It had a ring on top that had some holes for bolting the unit to the floor. I could use these holes to attach my spokes. The problem was there was a ring 3/4 of the way through the hole that kept the flange from slipping down the pipe. I'd have to remove that obstacle so I could slide it down the pipe. That wasn't as easy as it sounds. I finally had to use a chisel to remove it and sandpaper to smooth it down so it would slide.

I had lots of half inch pex plumbing parts left over from a plumbing project so I used pieces of pipe and flatened pieces of half inch copper pipe to attach to the ring using zap straps which allowed the spokes some flexibility to move with the waves. I put pex tees at the far end of the spokes.

I created the "ring" with pieces of pex pipe. I slid pieces of the kds noodle over the pieces of pipe. I found it was easier to bend the pipe if I filled it with sand and bent it to attach to the tees with a heat gun. That sounds easier than it was. But with a bit of persistence I managed to get it all together.