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

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.