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As PSK31 uses differential coding, it is the phase change over the
32ms signalling period due to freqeuncy error that is important. If for
BPSK, we need to maintain the phase to less than 90 degrees to remove the
ambiguity, so 90/360 / 32ms = 7.8Hz freq error permissible.
For noisy signals, the determination of correct phase becomes worse, so
error rate will progressively worsen with tuning error.
Andy G4JNT
----- Original Message -----
Sent: Saturday, December 11, 2004 10:12
AM
Subject: LF: Frequency errors on
PSK31
Hello.
I'm trying to produce a small PSK31 beacon on a PIC chip using one port
(and an XOR gate) to initiate phase change, and others to control the mark
space ratio for driving a class D amplifier for the amplitude change.
Question:
With the currently available soundcard decoders, what frequency
errors are permissable in the PSK31 waveform which will still decode
successfully? Normally 32ms but what tolerance is OK?
Do the decoders lock, and then suddenly lose all decoding ability if the
frequency is too far off, or do they just slowly increase their bit error rate
with frequency error?
73
David
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