What kind of codec makes the most sense to you? We have things like D-Star that
have existing hardware (the codec exists and is documented). Many really seem
to find it unusable since they have to pay for it. I find it odd that their
time to reinvent the wheel is somehow free.
Are there any other answers, such as the GSM codec? Echolink uses that, and
thus a path out of an echolink client to the ISS could be direct. I have a Java
version of the echolink client that I wrote quite a few years back that could be
used to investigate digital voice with other software codecs.
It would seem wise for the RF modulation scheme to have a reasonable FEC to try
and minimize retransmission. What kinds of modulation schemes would be easy to
put on board the ISS and potentially other craft that could be 100% hardware
based to minimize the "moving" parts? For example are there any existing "FPGA"
kind of device based SDR kits with "digital data modulation"? I've seen quite a
few that are based on complete programs running on Windows or other OSes. We'll
need something in hardened hardware I'd think.
Thoughts?
Gregg Wonderly
On 8/20/2011 9:10 PM, Phil Karn wrote:
On 8/19/11 7:51 AM, Gregg Wonderly wrote:
What kind of digital are you suggesting? Voice and data both? A
digital path from anywhere on the planet to the appropriate ground
station is easily doable with some "documentation" of the ground stations.
Digital voice would be the easiest to support since the data rate is so
modest. Low rate data (< 100 kb/s) wouldn't be much harder. All it takes
is a stabilized platform with microwave antennas. Any ground station
with an Internet connection could automatically link with the ISS and
relay it to a central point (e.g., Houston) and then hand it off to the
next ground station. One advantage we hams have always had over NASA
itself are our numbers and geographical distribution. We obviously
wouldn't be able to cover the large parts of the earth that are entirely
water but we could still do a pretty good job with the rest.
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