Author Topic: "What's all this AM-PM stuff all about, anyway?"  (Read 1775 times)

Gen. Dreedle

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"What's all this AM-PM stuff all about, anyway?"
« on: October 04, 2011, 04:47:02 PM »
This isn't intended to start a food fight about PIM, TIM, SID, and all that stuff. I am merely curious how many folks know anything about it.

Not whether or not it has any merit to amp design (we can argue about that in another thread), but how folks out there learned about stuff like this.

Did you learn about it at university? If so, where?

Did you learn about it at work. if so, what kind of work were you doing at that time?

If you learned it at university, what are the chances that it is still being taught? Most EE programmes are now Computer Eng. programmes. So, you would be exposed to it there in the future. No need for it. The world is all digital now, and we all know that it will be (bit) perfect. Forever.

What about where you worked? How many folks there still know anything about it? When they (or we!) are all gone, who is going to pass it down? They ran all the "microwave cowboys" off where I used to work. Does the video industry still care about it? It is all "digital", at least it is supposed to be as of one week ago. What about semicon companies? They got rid of Bob Pease, so what is their future? All they seem to care about these days is rail-rail operation, all the way down to 5 V (or 3.3 V, even worse). With so little headroom to work with, who can be bothered with such trivial details as AM-PM and AM-AM? Low voltage operation and low power consumption seem to the driving force in all new design. OK, they can make transistors smaller all the time, and most likely faster as a result. But at what cost? I would like to think that places like AD, Linear, and National have some pretty clever guys, who are coming up with innovative ways around those limitations. But what happens when the guys that learned from Bob Pease go the way of Bob Pease?

Bottom line is, no matter how you came about working with it, it will probably be one more form of analogue "art" that will go the way of the typewriter when all the old farts like me are gone.

Anyway, your thoughts, if any.
"Major Danby, sir."
"Danby. D-A-N-B-Y."
"Take him out and shoot him."
"Sir?"
"I said take him out and shoot him. Can't you hear?"

Gen. Dreedle

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Re: "What's all this AM-PM stuff all about, anyway?"
« Reply #1 on: October 04, 2011, 04:47:54 PM »
Oh, my turn: differential phase and gain measuring knobs on H-P microwave link analysers. Fall, 1973.

We never carried video traffic, but it told us other stuff about how the network was working.

Anyway........the day we got our 3577 network analyser, it didn't take me long to figure out that it would measure AM-PM. The first thing that I thought of was measuring a stereo amp.

Never did. Forget why.

Now that I have one, I don't. I forgot how to do it! (Maybe someday I will track down an operator's manual, and figure out how to do it. Too lazy to rack what little grey matter that I have left (due to insomnia) to figure out myself.)

That, and I am now too old to care!

(More about this subject in another thread. We'll give this one a day or so to rot, then move on.)
"Major Danby, sir."
"Danby. D-A-N-B-Y."
"Take him out and shoot him."
"Sir?"
"I said take him out and shoot him. Can't you hear?"

Gen. Dreedle

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Re: "What's all this AM-PM stuff all about, anyway?"
« Reply #2 on: October 04, 2011, 04:48:50 PM »
I can tell he doesn't go where I did.

The word "RF" did not even exist.
"Major Danby, sir."
"Danby. D-A-N-B-Y."
"Take him out and shoot him."
"Sir?"
"I said take him out and shoot him. Can't you hear?"

Gen. Dreedle

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Re: "What's all this AM-PM stuff all about, anyway?"
« Reply #3 on: October 04, 2011, 04:49:50 PM »
Where I went.....stinking dump that it was and probably still is...........unless you were interested in control theory, you were SOL. None of those other disciplines were available, even at the graduate level. I did have one decent course on IC electronics, taught by the only prof who had real-world experience. The rest were weenies that went on to take grad course as soon as they could, and somehow parlayed that into becoming an associate professor. One of them is still only an "associate" professor! 40 years later. The rest made it to full professor.

I see from the alumni crap that I can not un-subscribe from, that they have gone over the world of computer engineering. Even changed the name of the Dept. to ECE. (Figure out what that stands for.) In a nutshell, they were too busy trying to 'splain the benefits of joining the IEEE than they were 'splaining anything of value.

Typical day in control theory class. (Any year, any course, on any given day.)

"So, how do I tell if my amp has poles in the right-hand plane or not?"
"That is beyond the scope of this course."
"You said that last course. When will it be the scope of a course?"
"We have been over this before, and............"
"And we are going to go over it again. I want to know how I can tell if my amp is going to blow up before I turn it on. Not after I smoke a bunch of $5 output devices."

During one of my more heated tirades, I blurted out "Have you ever actually worked on anything electronic in your life, or just theorised about it?"

You can imagine the response that I got.

"Like the one above about the potato latke stand?"

Yeah.....something like that. The only reason why I graduated is because they counted on my tuition money.

That reminds me..................how many times have we heard about the "engineering shortage"????????? If you research who is putting out that crap, you find out that it is really a projected shortage of incoming engineering students.

Yeah, I had figured that scam out sometime in my sophomore year at university. They weren't going to flunk us out, because by that point they had weeded out the ones that needed to be weeded out, and the rest of..........

No matter what we did..........(and boy, did I do it!).......we were there for the next 2+ years.

They had already budgeted and spent that tuition money. Ergo, "So, are you ever going to tell me how to find out if I have poles in the right-hand plane?"

No, of course not. But I had paid for the privilege of asking it, and dammit, I was going to continue to ask it. Knew I was never going to get the answer, but they weren't going to get any peace, either.

And you guys wonder why I am so bitter. Tsk, tsk!
"Major Danby, sir."
"Danby. D-A-N-B-Y."
"Take him out and shoot him."
"Sir?"
"I said take him out and shoot him. Can't you hear?"

Gen. Dreedle

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Re: "What's all this AM-PM stuff all about, anyway?"
« Reply #4 on: October 04, 2011, 04:50:47 PM »
CG:

A book referenced in one of those AM-PM app notes is in my collection. Probably just for stating of modulation definitions and equations. I actually used it once at my real job, to verify BERT vs C/N on a system.

Fours years of sitting around, bored silly, finally paid off. Only took around 12 years.
"Major Danby, sir."
"Danby. D-A-N-B-Y."
"Take him out and shoot him."
"Sir?"
"I said take him out and shoot him. Can't you hear?"