AM Modulation

The LDR voltage divider is a time-variant gain. That's all you need to produce modulation, and clearly this circuit does deliver an amplitude-modulated sine wave.

You could feed a signal generator into an audio amplifier and turn the volume control manually, up and down in a roughly sinusoidal way, and you'd hear the volume going up and down. And if you spectrum analyzed that, you'd see the sidebands. Same thing.

John

Didn't someone on here post a simulation of a pot with the shaft programmed to go back and forth at about 1kHz? ;-)

Tim

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

"Don Bowey"

** Bowey = a pig arrogant, congenital moron who thinks ONLY in cliches.

IOW - a septic tank "ham".

....... Phil

Speaking for myself, I hate the way you pollute this forum by changing the SUBJECT: headings to carry your putrid messages. Even if we chose not to click on your ugly posts, we're still required to read your filth. Kindly cut it out.

--
 Thanks,
    - Win

"Winfield Hill"

** The only thing Win ever does.

** Entirely appropriate and my privilege any time the subject matter of the post becomes un-related to the original heading.

If you examine the prior post I am replying to you can see why.

It is also correct usenet practice.

** So Win prefers to see no longer relevant technical headings on posts that contain no tech info ??

Maybe I should post my favourite Pizza recipe under:

"Planar Multi-Component Fabrication with Thermal Fusing" ?

** Dunno how your newsreader presents a NG thread - but what you say is simply NOT true of most including OE.

BTW

You are nothing but a whining, posturing ass - Win.

You have no clue what a open, public forum is about.

Go find a moderated "electronics design" forum if your sensibilities are so damn delicate.

....... Phil

Sheeeesh! I'll post one at ~1+ Ghz

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

--
Yes, it is.

--
The LDR is the multiplier which provides the product.

It's amazing how when people call others foul names, they are actually describing themselves.

--
 Thanks,
    - Win

"Winfield Hill"

** The only thing Win ever does.

** Entirely appropriate and my privilege any time the subject matter of the post becomes un-related to the original heading.

If you examine the prior post I am replying to you can see why.

It is also correct usenet practice.

** So Win prefers to see no longer relevant technical headings on posts that contain no tech info ??

Maybe I should post my favourite Pizza recipe under:

"Planar Multi-Component Fabrication with Thermal Fusing" ?

** Dunno how your newsreader presents a NG thread - but what you say is simply NOT true of most including OE.

BTW 1

You are nothing but a whining, posturing ass - Win.

You have no clue what a open, public forum is about.

Go find a moderated "electronics design" forum if your sensibilities are so damn delicate.

BTW 2

"Winfield" is a brand of fag made famous in a series of slightly OTT magazine and TV ads featuring that Aussie icon - Paul Hogan (aka Crocodile Dundee).

Kinda hilarious ain't it?

....... Phil

Ummm? Just filter on "author" ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

In article , Rich Grise wrote: [... cilantro ...]

No, cilantro does not taste like soap and it is much easier to grow than either parsley or oregano.

It tastes like gasoline.

--
--
kensmith@rahul.net   forging knowledge

Alton Brown, on "Good Eats" last night, said that Coriander SEEDS grow to be Cilantro LEAVES.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Question for you analytical types: what would the spectrum look like for a sine wave that is ever, linearly increasing in amplitude?

v = t * sin(w*t)

John

When it's in a voltage divider, it multiplies. ;-)

--
  Keith

I don't know about that, but if you modulate a TWT with a sawtooth, it's called "serrodyne modulation", and it makes a little baby spectrum (which in jamming transmitters is called the "package") split off and march up the band, confusing Doppler radar.

Cheers! Rich

Of course the integral doesn't converge, but by analytic continuation you can do it--you just chuck in a factor of exp(-epsilon*t) and let epsilon go to 0 after taking the integral--the net result is to chop off all the contributions from the t=infinity limit. I assume you want it to turn on at t=0, so the amplitude is t*H(t), where H(t) is the unit step function.

g'(t) = H(t) has transform G'(f) = i/(2*pi*f), so g(t) = t*H(t) has transform G(f) = -1/(2*pi*f)**2,

and sin(2*pi*F*t) has transform 0.5*(delta(f+F)-delta(f+F)),

so theoretically (by the convolution theorem)

v(t) = t sin(wt) has transform 1 ( 1 1 ) -------- ( ------- - -------- ) 8*pi**2 ( (f-F)**2 (f+F)**2 )

(Modulo a possible sign.)

Cheers,

Phil Hobbs

I did it graphically (the MIT method), and I agree with your result... "circus tent" skirts ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Has you mother never taught you not to swear or to use foul language?

Meindert