On Tue, 21 Feb 2006 12:29:25 -0500, Scott in Baltimore
wrote in
:

******
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)


It's about time to put this argument to rest...... you're both right.
The amplitude of the -signal- changes according to the modulation, but
the -carrier- is steady. The difference is that the signal (as seen on
an o-scope) is the vector sum of the carrier and the sidebands, while
the -carrier- (as seen on the spectrum analyzer) is only an isolated
component of the total signal.

Does that clear things up a bit?







----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----