Do any of you oldtimers remember the spherical dishes that the homebrewers were building when Bob Cooper was just a teenager? For those not so old, TVRO (Television Receive Only) was the term used to describe the first backyard satellite dishes. Just about everyone involved in it was an electronics buff that had built ham equipment. The plans and construction article I read were in a Popular Electronics project written by Coop himself.
The spherical dish could be thought of as a section cut out of a big basketball 50 feet in diameter and supported by a stationary wooden framework. It looked to the untrained eye (today's HOA) like a flower trellis. It was tilted back at the top so as to reflect the satellite signal to an LNA about 25 feet away on a post about 6' tall. Each satellite had it's own LAN or you moved the post to what satellite you wanted to watch. The post locations, or additional posts were marked to simplify the positioning of a single LNA. You mowed your yard very carefully because of the coax running across he backyard.
The dish's reflective surface was 1/4" square mesh hardware cloth (C band). Today you'd have to cover it with 1/16" mesh aluminum screen wire for Ku band. The only Ku band around back then were the radar guns that the local Police used for speed limit control The hardware cloth was stapled or tacked to thin strips of redwood or cedar that were suspended above the framework on allthread rods that could be adjusted in or out to fit the radius of the sphere. The center of the sphere was the focal point. During construction, or later tweaking and retuning, a string was tied at the focalpoint and stretched towards the screen surface. The allthread was threaded in or out to make the wood strip touch the free end of the string, which might have a plumb bob or something similar on the free end.
Don't know how many of these were built, but for several years there weren't many surplus or used dishes around.
Harold
The spherical dish could be thought of as a section cut out of a big basketball 50 feet in diameter and supported by a stationary wooden framework. It looked to the untrained eye (today's HOA) like a flower trellis. It was tilted back at the top so as to reflect the satellite signal to an LNA about 25 feet away on a post about 6' tall. Each satellite had it's own LAN or you moved the post to what satellite you wanted to watch. The post locations, or additional posts were marked to simplify the positioning of a single LNA. You mowed your yard very carefully because of the coax running across he backyard.
The dish's reflective surface was 1/4" square mesh hardware cloth (C band). Today you'd have to cover it with 1/16" mesh aluminum screen wire for Ku band. The only Ku band around back then were the radar guns that the local Police used for speed limit control The hardware cloth was stapled or tacked to thin strips of redwood or cedar that were suspended above the framework on allthread rods that could be adjusted in or out to fit the radius of the sphere. The center of the sphere was the focal point. During construction, or later tweaking and retuning, a string was tied at the focalpoint and stretched towards the screen surface. The allthread was threaded in or out to make the wood strip touch the free end of the string, which might have a plumb bob or something similar on the free end.
Don't know how many of these were built, but for several years there weren't many surplus or used dishes around.
Harold