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Peter Antypas 2021-11-29 07:00:07 -08:00
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@ -19,11 +19,11 @@ So with all the core functionality kept outside and under tight control, the onl
### Mechanical
The antenna casing that you see in these photos is a piece of 1" Schedule 40 "furniture" grade PVC pipe. It is simply the most inexpensive UV resistant material available, and it looks great too!
The VHF antenna whip is built using an epoxy wound filament tube coated with high grade US-made irradiated polyolefin ("heat shrink") tubing. The company that makes this tubing (and helped me with this design challenge) also built the landing gear for NASA's Ingenuity helicopter on Mars, so they definitely understand how to deal with harsh environments. The bottomline is that unlike typical fiberglass antenna masts you might see around (or have on your boat already), this antenna is not going to degrade and "blossom" under continuous sun exposure.
The VHF antenna whip is built using an epoxy wound filament tube coated with high quality, UV resistant irradiated polyolefin ("heat shrink"). The company that makes this tubing (and helped me with this design challenge) also built the landing gear for NASA's Ingenuity helicopter on Mars, so they definitely understand how to deal with harsh environments. The bottomline is that unlike typical fiberglass antenna masts, this antenna is not going to degrade and "blossom" under continuous sun exposure.
The entire outdoor assembly is held together by the same high grade heat shrink tubing, so there is no need for any adhesives! The main water seal is formed by heat shrinking around a specially designed 3D printed cap made of PLA. This part naturally softens when heated and is also compressed by the heat shrink tubin surrounding it, thus forming a permanent, watertight colar around the antenna tube. This blocks rain water and salt spray from the top. A layer of clear heat shrink in the interior forms a secondary water seal encompassing the lower part of the antenna. Finally, the PCB can be sprayed with conformal coating for an added layer of protection.
The entire outdoor assembly is held together by the same high grade heat shrink tubing, so there is no need for any adhesives! The main water seal is formed by heat shrinking around a specially designed 3D printed cap made of PLA. This part naturally softens when heated and as it's compressed by the heat shrink tubing surrounding it, it forms a permanent, watertight colar around the antenna tube. This blocks rain water and salt spray from the top. A layer of clear heat shrink in the interior forms a secondary water seal encompassing the lower part of the antenna. Finally, the PCB can be sprayed with conformal coating for an added layer of protection.
With no adhesives getting in the way, the unit can actually be opened and serviced by (carefully) cutting through the heat shrink tubing with a knife, then resealing with the same material and method as before.
With no adhesives getting in the way, the unit can actually be opened and serviced by (carefully) cutting through the heat shrink tubing with a knife, then resealing with the same material and method as before. That was one of my design goals from the beginning.
### Electrical