On Tue, Sep 21, 2010 at 7:57 AM, Charles Brabham <[email protected]> wrote:
> Q15x25 mode uses fifteen PSK streams to return an effective 2500 baud data > rate - if all goes well. In tests on HF, Q15x25 was not very robust at all. > It would work well with a strong, clean link but under typical HF conditions > it slowed down considerably. In some conditions, HF Packet at 300 baud > provided better throughput than Q15x25 mode at 2500 baud. > > As in the story of the tortoise and the hare, an emphasis on getting > through can be much more productive than concentrating all effort upon > simply going faster... Sometimes less is more. > The problem is, HF propagation through the ionosphere is NOT a gaussian-noise-limited channel. Fast PSK does NOT usually fare well over HF. FWIW it would be good for LoS VHF/UHF communications. If you are interested in fast datacomm over HF you need to study what has been accomplished with PACTOR and WinMOR. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 [email protected] +1.767.617.1365 (Dominica) +1.931.492.6776 (USA) (+1.931.4.WB6RQN)
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