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AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
On Jun 30, 7:43 pm, Jeff Liebermann wrote:
The carrier does NOT vary in amplitude. If it did, that would be modulating the carrier, which is the job of the modulator, not whatever is producing the carrier. Exactly. The modulator signal modulates the carrier wave. If there is no modulator signal, then the carrier does not vary by amplitude or by anything. One poster stated that the signal with the higher-frequency is automatically the carrier wave while the signal with the lower- frequency is automatically the modulator wave. This is not true. What I was trying to say is that an AM radio carrier wave cannot vary significantly by anything other than its amplitude [though, as one poster pointed out, the AM carrier can experience extremely-negligible variations in frequency]. If an AM radio signal has that restriction, it is the carrier wave. If an AM radio signal does not have that restriction, then it is the modulator wave. This is true, even if the AM carrier wave is of a lower-frequency than the modulator wave. That's what I was trying to say. In AM radio, determining which is the carrier wave and which is the modulator wave is not by which has the higher frequency but rather by which has the restriction that I stated. If there is no modulator signal, then no carrier signal of any type [AM, FM, etc.] will vary by any quality [frequency, amplitude, phase, etc.] |
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AM electromagnetic waves: 20 KHz modulation frequency on anastronomically-low carrier frequency
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AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
Radium hath wroth:
On Jun 30, 7:43 pm, Jeff Liebermann wrote: The carrier does NOT vary in amplitude. If it did, that would be modulating the carrier, which is the job of the modulator, not whatever is producing the carrier. Exactly. The modulator signal modulates the carrier wave. If there is no modulator signal, then the carrier does not vary by amplitude or by anything. Brilliant. Yes, if there is no signal input, there's no change in output. Incidentally, in an AM system, the carrier does NOT change. You can see that on a spectrum analyzer. Modulate all you want and the carrier stays put at 50% of the total power output. The rest of the power is split between the upper and lower side bands. If there is no modulation input, then the side bands disappear, but the carrier just stays there. As someone mentioned, there is usually some residual FM on the carrier usually caused by sloppy power supply regulation. Also, some synthesizer noise. A well designed AM broadcast transmitter doesn't have much of this junk present. The problem is that the FM that appears on the carrier also appears on all the side bands. It doesn't hurt if the carrier has a little residual FM, but any such junk on the sidebands will result in a substantial increase in audible noise by mixing with the audio. One poster stated that the signal with the higher-frequency is automatically the carrier wave while the signal with the lower- frequency is automatically the modulator wave. That was me. This is not true. Prove it. I explained how it works and why quite adequately. I didn't even need to resort to formulas and calculations. The multiplier (mixer) modulator inputs are symmetrical and identical. Therefore the inputs are also symmetrical and indistinguishable. I also provided a simple audio test you can do in your spare time to demonstrate how it works. Now, convince me that the multiplier (mixer) waveform would be different depending on which input was the carrier or modulation. What I was trying to say is that an AM radio carrier wave cannot vary significantly by anything other than its amplitude [though, as one poster pointed out, the AM carrier can experience extremely-negligible variations in frequency]. If an AM radio signal has that restriction, it is the carrier wave. If an AM radio signal does not have that restriction, then it is the modulator wave. This is true, even if the AM carrier wave is of a lower-frequency than the modulator wave. That's what I was trying to say. I give up. What you've done is created a word salad. That's where you have a mess of buzzwords, shredded together, mixed with some window dressing, and served in a manner to imply that you have a clue what you're disgorging. Even the most basic concepts are not sinking in. You've also ignored multiple suggestions to read some very fine sources on how RF and modulation works. Open book, insert face, and come back when you have a clue as to the basics. In AM radio, determining which is the carrier wave and which is the modulator wave is not by which has the higher frequency but rather by which has the restriction that I stated. Wrong. With AM it's easy. The higher frequency is always the carrier. Can you give me a diagram or a commonly used communications system where the reverse might be true? I can't. If there is no modulator signal, then no carrier signal of any type [AM, FM, etc.] will vary by any quality [frequency, amplitude, phase, etc.] Yawn... -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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