40M Loading Coil for AT-271 folding antenna.

thingiverse

UPDATE: Two new variations on the coil are added for someone who wants to use it for a screwdriver antenna. The coil should measure about 50uh. A plain interior is designed because it's believed that the center should contain supporting structure such as ABS plumbing pipe or a wooden dowel epoxied in place. The bending load on something this long will be considerable, so better interior support will definitely be required. NOTE: Updated information removes Glue Together assembly instructions. If you downloaded the files before midnight on Monday May 29th, you may want to re-download the files to get the latest version. Please read the instructions below for the latest assembly instructions. A loading coil is designed for the fold-up PRC Antenna pictured. This antenna is very lightweight and when horizontal it only droops about 4 inches. It's 113.5 inches long (2.88M). The AT-271 "Fishing Pole" antenna was used on the PRC-25 and PRC-77 Squad Radios, also on the PRC-104 HF radio. A number of commercial radios use the AT-271. See http://www.prc68.com/I/AT271.shtml for more details. The antenna, with all 7 sections extended, operates at 25Mhz. The loading coil at 22uh brings the operating frequency into the 40M band (7Mhz). It was designed to be 25uh total, so it can easily be fine-tuned by shorting out a few coils with a clip to one end.