[amsat-bb] FM Voice and Packet Satellites

Alan wa4sca at gmail.com
Tue Apr 18 14:18:35 UTC 2017

Back in the days when Pluto was still a planet, and I had hair, circa 1988,
there were two types of questions which were repeatedly asked of the
satellite builders:

1. Why do you keep making me build a new modem to copy data every time you
build a new satellite? Can't you just use a TNC? Why not fly a W0RLI packet

2. Why can't you just build a flying FM repeater, so I can use my regular

The techies who built satellites explained patiently both of these were
Really Bad Ideas; both are extremely poor choices from a technical
standpoint. They are single channel, and use one of the most inefficient
modulation schemes known to hams. We have spent the past 25+ years proving
the techies were right on both accounts. Consider the numerous detailed
discussions concerning problems with both over the past few days. Those
techies would be, and perhaps in some cases are, nodding knowingly at seeing
the validity of those objections being born out.

But the users have also been proven right. Satellite APRS manages to work
despite these limitations, and FM satellites are often in use AOS to LOS
with normally good cooperation. (Everybody is a newbie sometime.) The
ability to use rather simple equipment, easily understood, has won out over
technically "sweeter" solutions. Users have tacitly decided that the
limitations are a good tradeoff. The proof is the number of successful QSOs
and Dxpeditions reported. However, the limitations are inherent in the
chosen technology, and education, innovation, consensus, and courtesy can
only do so much.

Keep in mind there are other voice options in the form of linear satellites
now, and with only slightly greater complexity. You can chase DX, grids, and
rag chew at the same time without taking away resources from other users.

To borrow a phrase from AMSAT-NA's Official Curmudgeon,  Tom, K3IO, "But
wait, there's more!" Digital voice and data systems are being developed by
the current generation of techies which will make microwave systems, and the
resulting bandwidth, available to the everyone using digital signal
processing and eBay parts. As Phil Karn, KA9Q, puts it, any sufficiently
advanced modulation scheme is indistinguishable from noise. But with that
noise will come the ability to accommodate voice, TV, and data
simultaneously. For some, the tradeoff of greater complexity for almost
unbelievable capability will be worth it. For others, simplicity and
familiarity will win out. In both cases, that is in the best traditions of
amateur radio.


Curmudgeon (jg)

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