[amsat-bb] Re: Turn off AGC when receiving BPSK-1000

[Gregg Wonderly]

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.
>
>