Path: utzoo!utgpu!watserv1!watmath!att!occrsh!uokmax!apple!usc!cs.utexas.edu!asuvax!anasaz!qip!john
From: john@qip.UUCP (John Moore)
Newsgroups: sci.electronics
Subject: Re: Along the heterodyne lines, what about "FM" synthesis?
Message-ID: <4487@qip.UUCP>
Date: 11 Sep 90 21:35:34 GMT
References: <1040@beguine.UUCP>
Reply-To: john@qip.UUCP (John Moore)
Organization: Anasazi Inc, Phoenix AZ
Lines: 23

In article <1040@beguine.UUCP> Jeff.Miller@samba.acs.unc.edu (BBS Account) writes:
]Comming from more of an EE background, explanations of FM synthesis
]such as used in the Yamaha DX-7 (mostly by musicians) leave me
]confused. I suspect that what Yamaha passes off as "FM" synthesis
]would be far better described as AM synthesis. 
] 
]People have said "One frequency modulates another." But how how? By
]instantaneous multiplication, like an AM transmitter, or deos one
]frequency wiggle the other in the _frequency_ domain, like an FM
]transmitter? 
I believe the Yamaha uses "Chowning" synthesis. In that method, you
do in fact instantaneously modulate the frequency of one signal
with another. FM modulation gives different effects than AM
modulation. For one thing, a sine wave modulating another sine wave
may have an infinite number of sidebands.

The modulation can be performed all sorts of ways. Basically, just
feed the modulating frequency to a VFO, and you get it.
-- 
John Moore HAM:NJ7E/CAP:T-Bird 381 {ames!ncar!noao!asuvax,mcdphx}!anasaz!john 
USnail: 7525 Clearwater Pkwy, Scottsdale,AZ 85253 anasaz!john@asuvax.eas.asu.edu
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