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Re: Fade remover



>Since the command stations will never do any
>of this, we are all wasting amsat-bb bandwidth.

This strikes a real nerve with me, and I can't resist the need to vent
any longer.

Years ago, I started lobbying the P3D powers-that-be to use more
efficient downlink modulation and coding.  Although the P3D IHU is
nearly identical to the mid-1970s design that flew on Phase 3A, nearly
all of the complexity associated with FEC is on the receiving
end. Thanks to a few minor advances in personal computing technology
over the past quarter century, we can now easily handle those
complexities. That gave us the opportunity to vastly improve
spacecraft downlink performance, especially under fading conditions,
with only a software change to the spacecraft.

I was told not to fix things that aren't broken. I responded that few
amateur spacecraft went into operation without a hitch, and that
amateur satellite downlink budgets are often overly optimistic. For
example, after the AO-10 launch many stations had difficulty receiving
error-free telemetry because of the spacecraft's damaged 2m antenna,
abnormal attitude and spin.  Having the extra downlink margin for a
spacecraft as complex as P3D might be good insurance. And I was
willing to write the necessary ground software. I'd already done the
hard parts, including several Viterbi and Reed-Solomon decoders.

I got nowhere. One insider responded, "You know perfectly well why the
Phase 3 links are the way they are. That's my last comment on the
subject."

To say that such an insular attitude can only demoralize volunteers
and discourage contributions to a project that relies on them is an
understatement, at best. There was a time when I'd take this as a
challenge, to see just what I could do within the constraints of the
existing design.

But now I think, "Why bother?" After all, it's now almost 3 months
after the launch and the team has yet to publicly disclose all the
material information they have about the propulsion system
problems. They obviously don't want our help, so why should we force
it on them?

Phil





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