POWER. How much is enough? LA2QAA Feb 2006
There could be many answers to that question but the correct one regarding amateur satellite communications is:
"Just enough to maintain effective communications".
For instance, how many people reduce their power as the satellite they're operating on approches TCA (time of closest approach). A good operator will, because they know that the use of excessive power is *not* good for the transponder. Case in point. When AO-7 first comes up over the horizon you'll probably need "X" amount of power to communicate effectively.
However, after 10-15 minutes, as the range decreases you'll find that a 3dB (50%) reduction of power will have no effect whatsoever on the signal. A *VERY* sensitive S-meter might show a difference but your ears certainly won't. Hands up those that actually regulate their power to maintain effective communications. (No, I didn't think so). You should try it sometime, you might get a surprise.
By the way, we do know (don't we?) why most satellites have a beacon?. The principal reason for a beacon is so that you can regulate your power to be consistent with that beacon, it's your reference. No signal should ever be more powerful than the beacon. That's what it's there for. Naturally, it will also serve as your propagation reference.
The basic principles of aerial gain are explained at ... Antenna Systems
73 John
LA2QAA@AMSAT.ORG