[sdiy] frequency shifters...

[John L Marshall]

A frequency shifter is similar to a balanced modulator except that the sum
and difference frequencies are separate. A ramp will an all harmonics
overtone series, 1kHz, 2kHz, 3kHz, 4kHz an so on. Frequency shifted by 100
Hz up will yield 1.1kHz, 2.1kHz, 3.1kHz, 4.1kHz and so on.

The same ramp frequency modulated will yield an infinite series of sidebands
at 100 Hz multiples from the 1kHz, 2kHz, and so on. The amplitude of the
various sidebands depends on the amplitude relationship between the 1kHz
carrier and the 100Hz modulator, the modulation index. This is not
intuitive.

Any VCO can produce FM. Inject a second oscillator in to the CV input. It is
best if the CV input is linear.

Frequency shifting can be accomplished with a couple of balanced modulators,
a quadrature oscillator and 90 degree phase difference network.

Take care,
John
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Pacific Northwest DIY Synthesizer meeting, July 20, 2002
See: www.sound-photo.com
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----- Original Message -----
From: <Nihiliste9 at aol.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, July 20, 2002 6:03 PM
Subject: [sdiy] frequency shifters...


> Hi all. I was wondering if frequency modulation was the same as a
frequency shifter. Also are there any kits out there for building them?
>
> thanks
> edward s.
>