Hi all,
On 9/1/2018 1:58 PM, Jim Brown wrote:
On 9/1/2018 3:14 AM, Iztok Saje wrote:
Instead of overcomplicating protocols, diversity reception shall be
considered.
Diversity reception has been around for nearly a century, and depends on
the very complex computing engine located between the ears of the
operator. My guess is that any decoding dependent on diversity reception
would be equally complex. The outputs of the two receivers can NOT
simply be added, because they are not time coherent, nor is the
difference between their two signal paths anything approaching constant.
This problem would seem to require two complete decoding systems whose
outputs are compared to provide a decoded signal to the operator.
It's worth mentioning that for more than a decade MAP65, a sister
program of WSJT, WSPR, and WSJT-X, has provided a powerful and uniquely
effective form of diversity reception: polarization diversity. And yes,
the outputs of two receivers ARE simply be added, with appropriate
weighting.
As anyone who has used MAP65 knows, this software yields a *huge*
advantage reception of linearly polarized signals over the
Earth-Moon-Earth path. Linear combinations of signals originating in
two orthogonally polarized antennas allow one to steer the received
polarization to any desired angle. MAP65 does this independently for
each and every signal in the received passband, which can be up to 90
kHz. Especially on the 2-meter band, top scorers in worldwide EME
contests nearly always use MAP65.
For those interested, more details may be found in references 10 and 11
here: https://physics.princeton.edu/pulsar/k1jt/refs.html
-- 73, Joe, K1JT
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