Ground plane foldable antenna 120-470 MHz 1/4 Wave

thingiverse

This an attempt to create a foldable 1/4 wave ground plane antenna for frequency range 120 - 470 MHz.The range of the frequency depends on how much do you stretch the antennae. After unfolding six of antennae it keeps the 135 degrees angle between the vertical monopole and radials. This means that it has 50Ω impedance.The construction does not need soldering. It is designed to be printed WITHOUT any support. Use PET filament, 20% infill if you're planning to handle it gently or 100% (or even try to remelt in salt) in any other case :)To connect the cable you need to strip at least 15 cm of the shield and thread it through the side hole from the bottom and connect all six radials with mounting screws around one after another .The center cable needs to be threaded via the center hole upwards and then the center antenna needs to be pressed down from the top and tightened with a screw. See pictures.This in not designed to work outdoor in various weather conditions. The construction is not water resistant, it also won't resist the strong winds. I wanted to test my handheld transceiver outside with something better than the stock rubber duck antenna but easy to carry.BOM (including modifications described at the end):6x 7mm diameter telescopic antenna with joint (type 158 19-60cm),1x 6mm diameter telescopic straight antenna (type 150 15-64cm).Both antennae types have flat mounting plates at the end and 3mm hole.6x M3x10 bolt3x M3x15 bolt1x M3x10 bolt6x M3x5 boltPVC 20-20.5 mm water pipe (at least 2 meters)50Ω cable with a plug suitable for you transceiver.Here you can copy and modify the model for your needs:the basehttps://www.tinkercad.com/things/886NDRdj20W-ground-plane-antenna-base?sharecode=HJL9dK4pzkOMVV75jUCzjvnM3CQ11QcwpFiapIP4IBothe lockhttps://www.tinkercad.com/things/cAaOMDskmav-ground-plane-antenna-base-lock?sharecode=nfUZ7h-hZ_hCWEDG3UoeIzizCbUc9gS7DazIrGlKNV4Refer to: https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/Tests passed - this antenna is able to receive AIS signals from the distance ~30 km at 161,975 MHz (A channel) and 162,025 MHz (B channel). 01/03/2024 Added "a lock" which is designed to keep radials unfolded. It goes underneath the base and it locks radials when you slightly turn it left after unfolding radials. The additional tube keeps the lock in place on the pole, it's mounted with two M3x5 bolts.05/03/2024 Added a simple antenna tripod. Just cut three pieces of PVC pipe 45 degrees on both ends 40 cm long and connect it with the main pole using the tripod printed part. Use four M3x5 bolts.08/03/2024 Added a simple cable hook. Print two copies and mount it on the pole with about 40 cm distance between, lower upside down. It allows to wind up the cable. Use two M3x5 bolts.