On Tuesday, December 3, 2002, at 11:09 AM, Steve Schear wrote:
In the late 70s, I was at TRW we built inflatable (beach ball) antennas for a black project. About 1/3 of the balloon's inside surface was aluminized and the feed was simply snapped into place at the opposite side. The antenna could either be used hand-held or place in a ring mount on a flat surface. This sort of approach could work well for cell phones and WiFi cards with external antenna port. For cell phones the entire instrument could be placed in at the reflector's focus and operated via a mic/headset adapter (some older Nokia models have an external antenna port behind a small rubber plug on the rear.)
Clever, but a section of a sphere is not a section of a paraboloid, so how did you deal with the focus issues?
Perhaps the feed part had a secondary antenna (like a secondary mirror in a telescope to correct aberrations in the larger primary).
A spherical antenna is better than nothing, but not by much.
--Tim May
