Amplitude Modulation (AM) can you tell me how?

I have found a bunch of sine wave ascillator circuits, I still need to go through them and see which ones I want to use.
Most of the circuits use a 555 timer IC.

I keep finding the circuit below, it's from an electronics workbook.

I don't totally understand the wiring.
On the left side, we have -15V in, would +15 go to ground?
"Carrier in" and "audio in", would the other wire go to ground?
What exactly does the potentiometer do?
My FET is a MPF102 N channel. It's designed for audio thru VHF, so I think it's right in the range.
Any help? Comments?
Thanks, you guys are great!

BeerGuy...

Are you actually looking to build a pulse generator like the one used in the Meyer water-fuel system? If so check out this link:

Pule Generator

This may be more suited to what you're trying to do.

Originally posted by Beer_Guy
On the left side, we have -15V in, would +15 go to ground?

No it's just using -15 volts no need for +15 volts...

"Carrier in" and "audio in", would the other wire go to ground?

Yes the other wire should go to ground...

What exactly does the potentiometer do?

Basically it's used to balance the signal, you adjust it for optimum AM on the output measured with an O'scope...

Hope that helps...

Jedi Master, you truly are a jedi Master! Thanks....
One question, how do you put -15 volts in without putting +15 volts in? "circuit" means literally that it runs around and return to the source. If you have a minus, you need a plus too,,,, right?
I'm too used to the normal way of making schematics, this one throws me off a bit.

jtma508, the signal in this project has to be amplitude modulated. It also uses low power input, 12A is quite a bit more than I require.
Thanks for the link though,,,, interesting.

Originally posted by Beer_Guy
One question, how do you put -15 volts in without putting +15 volts in?

Basically all you need is a -15 volt supply, here is a diag for a -12 volt, I think all you need to do is change the zener diode from a 12 volt to a 15 volt regulator...

www.play-hookey.com...

I understand that schematic, but wouldn't the ground connection be the positive side?
I mean you can't just have -12V can you? There has to be 2 connections to make a circuit. I feel like I'm being stupid on this one, but I've been fooling with circuit building for the better part of 30 years.
There is always a positive and a negative, you can't run a circuit from just one wire from a power supply.
If I'm missing something here, talk to me like I'm twelve, "this wire goes here, and this wire goes here..."
I hope you understand, I'm not bitchin, just confused.....

As it says in the link...

Set your voltmeter to measure dc voltages up to 20 volts, and connect the black ground lead of the voltmeter to a ground connection. Connect the red input lead of the voltmeter to the -12 volt output bus.

Yes you can have just a - voltage, the powersupply in your pc has a -5 and a -12 volts...

Now if you were after a positive voltage, flip the 2 rectifier diodes around, you see it's the way they're connected, as it is in the curcuit they only conduct on the negative half on the sine wave, thus producing a negative voltage ( with respect to ground )...

You have to open your eyes...and see...I can't do it for you...

You just did,,
I understand now, thanks.

Is it difficult to build a function generator? I was curious about trying different frequencies and waveforms......

Originally posted by Beer_Guy

Is it difficult to build a function generator? I was curious about trying different frequencies and waveforms......

Depends on how complicated you want...

Here is a 1hz to 20mhz, that looks pretty simple enough to build...

www.web-ee.com...

*edit*

I haven't tried this but here is a program that "supposed" to use the output of a pc sound card to act as a function gererator...

www.marchandelec.com...

[edit on 30-5-2006 by Jedi_Master]

Wow, Nice! Simple too, I think I'll use that circuit.
I also like the idea of using the computer as a function generator, I could experiment right at my desk.

Thanks for the links!

The diode is needed for non-linear amplification, it is required

Originally posted by Beer_Guy
Can anyone tell me if this would work for simple amplitude modulation?

It's simply a ring modulator with the diodes removed.

if your a novice i suggest you read this pdf first, which gives theory and circuits used for moduatinga nd demodulaing signal from AM carrier.

classes.engineering.wustl.edu/2009/fall/ese331/331Project5.pdf