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Old February 25th 06, 02:52 PM posted to rec.radio.cb
Jay in the Mojave
 
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Default Cobra 25LTD Classic tune up

Hello Scott:

I think we are getting the Time Domain mixed up with the Frequency Domain.

My comment was on a Oscilloscope voltage measurements which are in the
time domain. Without the RF Carrier voltage being modulated, increasing
and decreasing you would not have modulation of course. I never said the
power in the carrier changes. Or maybe I said it poorly?!??!?!?

But by added in more modulation power, like I said will allow for the
finial rf amplifier to have more modulation power, allowing for more RF
Carrier to be fully modulated, if it can handle the extra power. Simple
stuff. More power and modulation kicking a high drive amp will cook!

I have seen where the radios have been somehow modified to allow
unlinear modulation, that is the upper and lower envelopes are not
identical, and the radios still sounds ok. Yeah I don't know what they
do for the swing mods?!??!!?!

I put in Amplitude Modulation Envelope into Goggle and got a bunch of
neat web sites on the subject.

Jay in the Great Mojave Desert, ....just down the road ah ways from the
fillin station.




Scott in Baltimore wrote:
******
The carrier in Double Sideband Full Carrier Amplitude Modulation
should remain constant during modulation. If not, then you have a far
greater problem.
james




Hello James:

No thats not how AM works. The Modulation increases and decreses the
amptitude during Modulation. Thats how double sidband full modulation
works. Look in a old ARRL Book.


Jay in the Mojave



Jay, I respectfully disagree.

An AM carrier doesn't change, just sidebands are added in the mixing
(modulation)
process, and the instantaneous voltage shown on an o-scope will be 4
times greater
then the carrier power itself. Since the audio added is 50% of the
carrier, the
RMS power will be 150% of the unmodulated carrier. The peak to peak
voltage is
greater. Put a 1000 Hz tone on a signal and look at it on spec-an.

(make sure to do this test with an unmodified radio, "swing kits" ruin
proper AM)