On 03/02/2014 01:18 PM, David Rowe wrote:
> Is interference (intentional or otherwise) by other users a problem ATM?
I've only heard one report. And the offending station was W1AW! OK, one
of the portable W1AW's run for ARRL's centennial, and no doubt a
volunteer or walk-in operator.
However, considering jamming is a classical method of approaching the
robustness question, if perhaps not a great fit for all of the ways our
signal will fail. Steve is obviously just getting up to speed on this.
The actual mode of failure isn't too different from his hypothesis. It's
frequency-selective fading of adjacent bands due to phase cancellation
from differential time of arrival of ionospheric reflections. I have on
my queue to experiment in improving this by receiving RHCP and LHCP
simultaneously, and combining them in the modem. But I've had that on my
queue for more than a year, so anyone else who wants to play with it is
welcome. And in any case, we want this mode to work for people without
eggbeater receive antennas.
> I've looked into interleavers but the nature of the HF multipath channel
> means the gains are small or zero.
How is your work on LDPC going?
Thanks
Bruce
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