Helix Feedhorn for 2.4GHz

This very simple 2.4 GHz dish feed is a helix with a cupped ground plane/feedhorn, it is based on a design by Jerry, K5OE (Brown, Gerald R. K5OE. A Helix Feed For Surplus MMDS Antennas, Proceedings of the AMSAT-NA 19th Space Symposium) Jerry's paper is available also on-line. I strongly advise you to read this excellent paper before attempting to do your own feed. The dish has a f/D of 0.34, that's why I opted for a 3.25 turn helix. The porpoise of the can (by the way, it is made with a 11 OZ /311g coffee can, diameter is 10 cm) is two fold, first to act as a cupped ground plane to increase the helix gain and second to act as a feedhorn to limit the spillover form the dish edge. The edge-of-dish-cutoff angle in my antenna is 16 degrees so the theoretical cup edge -for a cup with its base at the focus of the dish- is about 15 mm. In this case the base of the cup is 30 mm away from the dish focus, that's why the height as seen in the pictures is about 45 mm (the offset from focus plus the anti-spillover flange).

Copyright  � 2001 Antonio Fern�ndez