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eHam Forums => Digital => Topic started by: N5LB on November 23, 2000, 10:30:29 PM



Title: QPSK vs. BPSK
Post by: N5LB on November 23, 2000, 10:30:29 PM
Does anyone run QPSK on HF?  The mode is available in Digipan and others but I have never heard (seen) anyone using it.  Why?  Intuitively it seems as though QPSK would be faster.


Title: QPSK vs. BPSK
Post by: VE3IAY on November 26, 2000, 06:49:47 AM
Here is a quote from the help file for the original G3PLX PSK31 program (PSK31SBW):

"For paths where errors occur in bursts rather than randomly, PSK31 can be switched to use a convolutional code at the transmitter and a matching Viterbi decoder at the receiver. QPSK, with 4 phase-shifts instead of two, is used for this, but the bandwidth and text speed stay the same. The price paid for this robustness is a tighter frequency stability requirement and a delay of 640mS in the decoder."

Hope that helps explain things.

73, Rich
VE3IAY


Title: QPSK vs. BPSK
Post by: N3HKN on February 04, 2001, 04:35:26 PM
One of the problems is recognizing QPSK if you are in BPSK mode. Seems like a nice feature to add. The new feature would analyze the signal from a user specified list of modulation schemes. Thus you might be interested in looking for PSK31 and PSK64 signals and the program would tell you which one you were listening to.

N3HKN