Re: [amsat-bb] new digital mode?

["Assi Friedman" <4x1kx@xxxxxxxx>]

"new digital mode???"

Does anyone have a problem with the fact that the #1 reason we are all
licensed is the charter "to improve the state of the art" yet the last
significant state of the art improvement happened in the early 80's when
Lyle Johnson's group developed the 1200Baud modem in a world that used
300baud audio coupled land lines and wireless networks we limited to line
of sight VHF audio repeaters?

Since then, the high tech world blew past us and we are 'only' about 15
years behind! I do find it disturbing when we have lots of computing
resources and all we can discuss is 30.9bps and 5cps modes!

We learned a lot from the 1990's microsats (14 years ago) and some of the
lessons included:
1. Don't use a ham radio non-coherent receiver with discrete frequency
settings to decode BPSK signals
2. Don't use low data rates because the signal bandwidth compared with
Doppler shift is significant and the quantized frequency adjustment or
wideband filters are both performance dominating degradation factors. The
first causes phase shift which introduce bit errors as wide as the time it
takes the PLL to relock, the second increases the noise power and
therefore degrading the Eb/No required to decode the bits.
3. FEC!!! (need I say more)

Doesn't sound odd to the hams that we limited our hobby to what can be
done using $5 radioshack parts and a soundcard and a 15 year old TNC? We
boxed ourselves in a little box and refuse to leave it for god knows what
reason (we are cheap?)

Look at what microsats are doing out there at present. Small spacecraft,
not much bigger than the latest AMSAT microsat doing 1mbps to a decent
sized dish!

We need to wake up and gracefully part with the "if it doesn't work with
my soundcard or my grandfather's SSB spark generator - it aient ham"
paradigm!

Hams call out for high performance communications systems. Most of the
concepts are within technical reach, but most of these concepts will
actually require us to us a "data radio" utilizing coherent detection,
Costa's Loops and FEC decoders encoders. Not a soundcard that was designed
to give your kid a trip playing Doom3!

All the best and SHANA TOVA!
May this year bring a little more peace and prosperity for all on the
third rock from the Sun!

Assi
4x1kx/kk7kx
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