AM Modulation

"John Larkin"

** ROTFL

Larkin is one of the worst offenders !

The turd blusters & bullshits wildly and pretends no mistake exists.

Far worse than that - he tries to "shoot the messenger "as well.

Complete arse wipe.

....... Phil

On Mon, 20 Mar 2006 10:29:14 +1100, "Phil Allison" Gave us:

You're an idiot, Phil. You will never achieve escape velocity from your little world of idiocy either, even though the gravity is quite low.

I don't make a lot of mistakes in newsgroups because I qualify stuff I'm not sure about (use words like "maybe" when I'm not 100% sure), or just pose questions. Not that making mistakes in a newsgroup matters squat; it doesn't.

One way to separate people here is "those who sometimes ask questions" and "those who never do." Interesting correlation to personality: fatheads never ask questions.

Hey, show us some of the stuff you've designed.

John

Another classic is installing PVC pipe for an old style hot tub blower and blowing the piping all to hell with the brush sparking when the blower turns on.

--
Many thanks,

Don Lancaster                          voice phone: (928)428-4073
Synergetics   3860 West First Street   Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml   email: don@tinaja.com

Please visit my GURU\'s LAIR web site at http://www.tinaja.com

"John Larkin"

** Complete red-herring to never publicly admitting them. ** Whaaaaaaaaatttttt ??

That is the opinion of a egomaniac ARSEHOLE !!

Not only does the scum bag dish out BAD info in public forum - Larkin then does his utmost to stop others from correcting it or supplying useful advice.

Peeeeuuukeeeee ......

......... Phil

A requirement of multiplication in AM, is a non-linear device. That is what the Class C stage provides. In a properly biased class C stage current will flow during less than 180 degrees. If you try to modulate a Class A RF stage it will not be non-linear unless you overdrive it, so multiplication will not occur.

Don

Hmm, I think that's making an assumption about the class A stage. Local voltage feedback, or high PSRR (where the "supply" rail is modulated), for instance. If you have a circuit that amounts to a variable resistor, however, the output signal must be some factor of the supply voltage, no?

Seems to me, the important thing about class C amplifiers is they're typically running full out, so the supply voltage has a big effect on signal level, thus allowing amplitude modulation. Outside of saturation, constant current devices such as pentodes and transistors will tend to have less modulation (higher PSRR) than triodes or transistors wired for a resistive characteristic.

The extreme case would be a class D inverter where the output is either 0V or +V: always saturated. By varying +V, you clearly modulate the output amplitude. Yeah, seems to me saturation is a big part of it. It isn't required, though.

Tim

-- Deep Fryer: a very philosophical monk. Website:

"Roy L. Fuckwit "

** Poor Roy L has no idea who his dad or grandad even were.

Just some anonymous, desperate customers of a pox ridden, $2 w**re.

( Sorry for the previous over-estimate on the dollar value.)

...... Phil

In fact the perfect example is the quintessential analog voltage multiplier circuit, a FET in the "linear" range (typically fractional volts Vdss). Id is jointly proportional to Vds and Vg, not counting nonlinearities, which can be smoothed out with a little help.

That's an example of a class A device (current always flowing), high-level modulated (by varying Vds) and multiplies two signals, hence capable of producing AM. Viola ;-)

Tim

-- Deep Fryer: a very philosophical monk. Website:

"Don Bowey" = a MORON

** What a pile of absolute crap !!

Try reading this wiki ALL the way through - f*****ad.

You might learn a bit.

But I doubt it.

........ Phil

True. The problem was that the secondary school trigometry answers the OP's question rather neatly, but loses the carrier. If I had dug around long enough to find the wikipedia article (which essentially begs the questions that the OP was asking and is thus pretty much useless as an answer to the question) I could have dealt with matter more neatly.

As it was, I did know about suppressed carrier AM transmissions, and tried to save time by guessing that what the OP was seeing was just carrier break-through in such a system (I done enough work on analog multipliers to know that some cariier breakthrough is pretty much inevitable, and moist modulators/mixers are crap multipliers). So I got that bit of it wrong.

--
Bill Sloman, Nijmegen

By which one should understand that Phil can't follow it. If I dumbed down my posts to his level, the rest of the user-group would be bored silly.

Phil does seem to be projecting his own problems here.

--
Bill Sloman, Nijmegen

** What bit is being admitted here as true ?

That Da Slow Man posts asinine drivel all the time ?

That he is not acting like a "grown up" ?

That he refuses to face the real issue of his brain defect and stop posting his wacky misconceptions on usenet ?

** That trig explains nothing to a mental midget like the OP. ** This does not tally with the OP's actual Q one bit.

" when v see the o/p of a AM Modulated signal in frequency domain ,why there r three frequencies ? in spite of modulating signal is made of single frequency? "

** Da Slow Man f****it got it ALL wrong.

Then turned a simple error into a CRIME.

That is what ARSEHOLES like him do.

....... Phil

In fact when were at MickyWorld they told us that "MagicMountain" was the third highest "mountain" in the state. No, I didn't appreciate FL much.

--
    Keith

That's supposed to be impressive? That's normal much of the year 'round here.

--
  Keith

Show us some of the stuff you've designed.

John

Really, Phil, if you spend any significant amount of time as angry as you seem to be, not only will your life be shortened, the brief time you do have on Earth will be much less rewarding.

John

"John Larkin"

** First learn how to trim - arsehole.

Then learn to stick to the point/s in hand.

Don't make any asinine assumptions.

Don't give out f****it advice to anyone.

........ Phil

If we define a class A stage as having the active device always conducting, as most people do, the output (drain, plate, collector) signal swing is pretty much determined by input signal level, transconductance, and output load. So unless transconductance changes with Vcc, output amplitude is independent of Vcc. Gm *does* change with Vcc for triodes, but not a whole bunch, and changes very little for fets and bipolars.

A class C device is overdriven, saturates on the negative swings and cuts off on the positive ones. So p-p output into a tuned plate load is approximately 2*Vcc, which is why a class C stage makes a good, pretty linear modulator. Not to mention efficient.

As Clem would say, if you swing Vcc far enough to really modulate a class A stage, it jest ain't class A any more.

John