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Old March 18th 04, 05:21 AM
Tony Meloche
 
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S R wrote:

(snip)

Another strange sound is like a bubbles exploiting. I hear this only on
analog.



This is part and pracel of listening to Radio Marti, which broadcasts
from this country to Cuba. The bubbling sound is Cuban jamming. Not
very effective here, but we're close to the signal and far from the
jamming. Wonder how it sounds there?





Hey, what is AFC, X-TAL & Superheterodne???


AFC is Automatic Frequency Control. It "locks" the station freqency
to prevent drift, in theory. Sometimes it's a great help. Sometimes,
it's a hindrance. Most effective in FM radio.

I honestly don't know what X-Tal is.

Superheterodyne means "above heterodyne". Heterodyning involves
using two carrier waves at different frequencies. The sound created
between the two is a whistle or sine wave tone that rises or drops in
frequeny as you approach the "center" of the station's signal. Have you
seen old movies or cartons where someone is tuning a radio statin in,
and those swooping "weeeeeohhhhwaaahh"
tones until they get to the station? Those are heterodynes.
Superheterodybe circuitry eliminates it by using carrier waves above
audible frequencies, but they are still clearly heard in any SSB mode,
and are a great aid to tuning precisely.

Tony


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