[amsat-bb] Re: Turn off AGC when receiving BPSK-1000
w5ggw at cox.net
Mon Aug 22 08:52:38 PDT 2011
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.
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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