MOTM

Thru Zero FM sounds like linear FM. The only difference is that you
can have a much higher modulation index. On ordinary VCOs, linear
FM hits a natural barrier when the momentary frequeny hits the 0Hz
mark - it cannot get lower. So (with a symmetrical modulation
waveform) the modulation also cannot go higher than twice the
initial frequency. If you try to go higher, the modulation will clip
and all sorts of unpleasant things will happen. (Which can also
be interesting, of course)
With Thru Zero FM, on the circuit side you do what Scott describes:
You change th edirection of the VCO's waveform. Now what is
quite complicated on the circuit side is "just a natural extension"
of ordinary linear FM. You won't get a new quality of modulation,
but you will only come to the really interesting modulation
amount of FM when you have tru zero capabillity.

In practice, many circuits for thru zero FM produce a slight
glitch when they go thru zero. This might or might not be a good
thing, depending on the application.

JH.

-----Urspr\ufffdngliche Nachricht-----
Von: mmarsh100 <mmarsh@...>
An: <motm@yahoogroups.com>
Gesendet: Sonntag, 27. Januar 2002 18:56
Betreff: [motm] Re: future oscillators


> Thanks, Scott.  That sounds interesting - instant new waveforms...
>
> --- In motm@y..., Scott Juskiw <scott@t...> wrote:
> > At 12:58 AM +0000 2002/01/27, mmarsh100 wrote:
> > >What's cool about "through zero"?  I've heard it mentioned several
> > >times on the list but I still don't know what it refers to...
> > >
> > >Mike
> >
> > I've never had an oscillator capable of through zero FM, so I can't
> > comment on how it sounds. If I remember this correctly (brain isn't
> > as young as it used to be), the oscillator waveform changes
> direction
> > as the FM signal drives the frequency below zero Hz. With most
> > oscillators, the waveform will just continue in the same direction.
>
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