Subj : Satellite Antenna To : Spaceman Spiff From : Angus Mcleod Date : Mon Aug 23 2004 04:09 pm Re: Satellite Antenna By: Spaceman Spiff to All on Mon Aug 23 2004 10:24:00 > I am planning to make a NOAA orbital satellite receiving station to capture > some of those great satellite images. I will be using WX Sat for my computer > software, run the audio from a ICOM R7000 receiver. > > I am looking into what the best antenna would be. You have to make certain compromises. The best performance will utilize a high-gain antenna like a yagi, quagi, quad or axial-mode helix, but you will need to track the bird in AZ and EL with realtime positional updates on your rotors, most probably from realtime tracking software running through an interface. I went this route with a Yaesu G5400 twin-axis rotor connected to my PC through a Kansas City Tracker and driven by InstantTrack software. Dated stuff now, but state-of-the-art at the time. A friend who was into WX birds (as opposed to Ham) came over and said "I think is due soon". I fired up the system, selected that bird and tuned the radio to the downlink, and when David heard the signal he had to put ice on his head, because he'd *never* heard the signal that loud'n'clear before. On the other hand, that is an expen$ive way to go. If you can get acceptable signal quality with a fixed antenna, then go for it. It's much less complex, cumbersome, expensive, and high-maintainance. A pre-amp can boost a weak signal at a far lower cost than a two-axis positioning system, and since you don't need to switch it out-of-circuit for transmitting, it should be comparably less pricy than a switched one. There are a number of fixed antenna designs such as turnstile, crossed dipoles (with or without a groundplane) discone, and so forth that people have used with some success. One thing to consider is the maximum elevation your birds of interest are likely to show at your location. LEO birds can fly right over your head (90 deg EL) and be at just about any AZ. If you are interested in geosync birds they will appear in only a small section of the sky as seen from your site. This can influence the choice of antenna. In fact, if you are interested in only one particular bird geosync bird (or a small number) you can construct one (or a small number of) high gain antennas and fix them on the AZ/EL of the bird(s) of interest. --- þ Synchronet þ CQ DX! The ANJO BBS calling on 56K dial-up... .