Now onto our continuing story.......

[VE3FMC]

I *think* (keyword) I'm starting to understand....are you saying (if my math and logic is right looking at the numbers you have) the carrier should be set at 1/2 the modulation? (2 watt to 100% = 4 watt radio/ 7 watt, 14 amp.) Anything higher than 1/2 carrier to mod. will cause splatter or distortion? Or is it more intense than that?

You did pass that Extra test didn't you? 

[N9ZHW]

I *think* (keyword) I'm starting to understand....are you saying (if my math and logic is right looking at the numbers you have) the carrier should be set at 1/2 the modulation? (2 watt to 100% = 4 watt radio/ 7 watt, 14 amp.) Anything higher than 1/2 carrier to mod. will cause splatter or distortion? Or is it more intense than that?

[N4CR]

The first thing to understand is that it takes power to modulate a signal. If you change the carrier output without the corresponding change in modulating power you will either under or over modulate.

Without any circuit modifications, you can simulate under modulation by moving the microphone away from your mouth or whispering. With less audio drive, there will be a corresponding change in modulation yet the carrier amplitude doesn't change. You can simulate overmodulation (if the microphone circuit doesn't have a limiter) by yelling into the microphone.

The modulation ratio (% of modulation) is the ratio of voltages.

X = Peak to Peak voltage of no modulation
Y = Peak to Peak voltage of modulated signal.

Modulation percentage = Y-X / X (actually, this falls apart when you reach 100%)

Example:

Unmodulated signal is 1 volt P-P.
Modulated signal is 1.5 volt P-P.

Modulation percentage is 1.5 - 1 / 1, or .5

When you reach 100% modulation, you will be varying the peak to peak voltage of the carrier by 1x the peak to peak voltage of the unmodulated carrier. This results in twice the peak to peak voltage of the unmodulated carrier.

When this ratio is disturbed by modifications to either the modulation circuit or the carrier circuit you will either overmodulate or undermodulate.

Undermodulation leads to low audio levels in the detector on the receiving end.

Overmodulation leads to distortion in the form of flat topping of the carrier envelope. This happens when the modulation peak to peak voltage exceeds the peak to peak voltage of the unmodulated carrier. Flat topping is lost information. What you lost can never be recovered so it makes the output sound distorted. Extreme flat topping makes a sine wave start to look like a square wave. It also messes with the bandwidth of the envelope as the extra energy has to go somewhere. This is known as splatter.

For an AM signal, there is nothing better than limiting your modulation to 100%.

Compression of audio brings up the low level audio signals (whispering) and limits the high level audio peaks (yelling) to create an overall higher percentage of modulation. This is a better way to have a higher apparent power level than you actually have since it takes advantage of the full capabilities of the carrier modulation without causing flat topping. It saturates the modulator better under the varying conditions of normal speech.

[N9ZHW]

So how come it took you so long to give me advice I can use rather than complaining about everything I write? (Go read some of your resposes lately) I'll have to get verification on this.

[N4CR]

So how come it took you so long to give me advice I can use rather than complaining about everything I write?

Gee, that was almost like saying Thank You wasn't it?

I gave you knowledge before. You didn't like it, but I did. I also gave you advice. You didn't like that either, but I did.

Advice is like "Don't come in this room with your muddy boots on.". It might help you through life but it isn't factual.

Knowledge is like "The circumference of a circle can by calculated by multiplying the diameter by Pi". It's factual knowledge.

Think of this place like a dinner table for knowledge. If you come to the table with a bad attitude or come and drop a snake on the table, you'll get a rebuff and we'll kill the snake. If you come with hunger, we'll stick a plate of food in front of you. Only you get to choose how you come to the table. We get to choose if we will feed you. Generally, we feed everyone who comes to the table and is respectful.

Sometimes you are your own worst enemy.

[K1CJS]

Another troll thread.  Half of the posts are

"This user is currently ignored."