I spent yesterday morning with a group of students studying some properties of antennas, as part of one of our courses. One of the things we did was to measure the beamwidth of a typical satellite receiver – the sort of thing you stick on the roof of your house to get all the decent TV chanels.
Now, we had the dish, but the problem was to find the satellite. There are two ways of doing this.
Method A (Kind of)
1. Look up in a data-book the latitude and longitudes of the various TV satellites strewn around the earth.
2. Look at their positions with respect to your latitude and longitude and work out which ones you have a hope of actually seeing from your location.
3. Knowing the satellite’s position, and your position, work out the azimuth and elevation you’d expect to see the satellite at.
4. Position the dish outside and move it up to the appropriate elevation
5. Find yourself a compass. Locate magnetic north.
6. Go to another data-book, and look up the deviation of magnetic north from true north from your location.
7. Point the dish to the correct azimuth, and receive your signal.
Alternatively there is method B.
1. Look up http://www.dishpointer.com/, use the world map to find your exact location, select your satellite and, hey presto, it calculates azimuth and elevation for you, and even corrects for magnetic north so you can just set the bearing directly on your compass. Go find your satellite.
Where is the fun in that? Is Google breeding a generation of people unable to do useful tasks like account for deviation of true north from magnetic north, or looking up data in a book?
Anyway, we found our satellite, and got a nice signal from it, and even measured the antenna’s beamwidth by wiggling it around and looking at how much the signal dropped by. That bit at least was fun.