[PD] types of distortion
Martin Peach
martinrp at vax2.concordia.ca
Tue Jul 20 20:25:05 CEST 2004
pix wrote:
>... if anyone knows of a good description of all of the different
>distortions that come into play when an FM or AM radio signal is poorly
>recieved, please fill me in.
>
>
In AM the radio-frequency sine wave is Amplitude Modulated by the
signal. In the receiver if the local oscillator is not running at the
same frequency as the transmitter sine wave, you get sidebands in the
signal whose frequency is the difference between the remote and local
oscillators plus the frequency of the signal. This can be simulated in
pd by multiplying [*~] two signals together, one of which is a sine wave
[osc~], and the other is up to you. All the other distortions in radio
are mostly noise, a constant background with bursts from lightning and
motors. Whistlers are caused by lightning impulses bouncing around in
the earth's magnetic field: different frequencies travel at different
speeds, so the original click is smeared into a descending chirp of noise.
.
Martin.
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