Satellite antennas--when do you need a dish?

Factual Questions
1

People with the first satellite TV receivers had those big honking dishes in their back yard (I guess these are still around in more remote areas). One guy famously disguised his as a deck umbrella.

DirectTV uses a much smaller dish.

My GPS processes satellite signals and has no dish at all. Same for satellite radio, and the handheld satellite phones (like from defunct Iridium).

This doesn’t even cover the big arrays that scientists use that cover football fields.

So what is the difference, when do need a dish, and when do you need a really big dish?

2

AFAIK, the older dishes were so large because the signal from the satellite was much weaker than the signal that comes from the Dish Network or DirecTV satellites. GPS signals are literally everywhere so I would guess that the parabolic dish is not needed.

About 12 years ago when our family was still living in Minnesota a friend of my father came over to dinner and he had one of the small Dish Networkesque dishes with him. He wanted my father to invest, get in on the ground floor so to speak. For whatever reason, my father decided against it. It is one of the few regrets he has ever had.

3

I don’t know if the signals were weaker in the past. But I’m pretty sure antenna/dish sizes have decreased for two primary reasons:

  1. Higher frequency. As frequency goes up, the amount of signal area the antenna needs to intercept decreases for a given amount of gain.

  2. Lower noise front-end amplifiers. A low noise spec means you can decrease the power of the incoming signal, which means you can get by with a lower gain (and thus smaller) antenna.

4

Dish antennas are highly directional. So in general they are only useful for communicating to satellites in geo-synchronous orbit. There are exceptions where big dish antennas move to track the satellites but people at home generally don’t have these. GPS satellites are not in geo-synchronous orbit so directional antennas are not useful in listening to their signals.

5

Bandwidth is an issue as well. GPS requires much less data than a TV signal.

6

I know that DirecTV is a digital signal. Did the old large dishes work for an analog signal? Perhaps that affects the antenna design.

7

Those big dishes are available for both digital and analog. Probably the biggest visible difference (aside from the size) between those and the little DirecTV dishes is that the big ones are steerable. They can be moved among a collection of geosynchronous satellites, each carrying different programming.

8

Oh yeah, they are very directional. I bumped into my large one while mowing the lawn and it was totally useless. That is when I switched to DISH.

Those huge antennas the government has are for listening for signals from space.