phase angle convention

Given the consequences of hooking the phases up wrong in a power plant, I'm sort of glad they do!

Cheers,

Phil Hobbs

Joerg snipped-for-privacy@removethispacbell.net posted to sci.electronics.design:

Collector of drain impedances of even small RF amplifiers are rather small, but they usually use a transformer of some kind to get to antenna feed line impedances. I still believe in the maximum power transfer theorem.

The transformer is used to achieve the desired power output at a given voltage and use the current capabilities of the device to a healthy extent and not beyond. You can easily double the output power of a modern RF amp and then one of three things happen:

a. Nothing but the circuit breaker trips all the time. b. The federales come because you exceeded the licensed limits. c. The overtemp warning light comes on, followed by a shut-down or a loud bang.

Impedance matching, or the need for it, is probably one of the most widely misunderstood pieces of EE theory. Remember the thread in here around July

Usually in the opposite order :-(

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

Yes, I was thinking about the tube days. Red -> cherry red -> orange -> white -> KABLAM! (then the sound of flying glass)

With transistor amps the kablouie often comes first. But at least there is no glass flying about.

Yep, he sure did. There was actually an assistant professor who still kept disagreeing with me. Me being the lowly student. Then I asked him whether he could calculate the final amp stage of a modern AM transmitter at greater than 85% efficiency. I gave him a datasheet of a really big one so he would believe me that this was state-of-the-art. Well, he stared at the stuff, sweat beads showing up on the forehead ...

I've seen bits of plastic flying around. Well, I didn't actualy see it, but we found it after turning the power off. The +12 and -12 supply wires were swapped. A 1488 had a neat conical hole in the top of the package. There wasn't any smoke, but there was a loud snap, loud enough so that neither of us had any question that something bad had happened.

If I was going to do that on a production line, I think safety glasses would be a good idea.