4 ms·

We got similar speeds with $5 chips from TI (although the antennas on both ends cost more than $5!). With nicer hardware, speeds in the hundreds of kilobits and

We got similar speeds with $5 chips from TI (although the antennas on both ends cost more than $5!). With nicer hardware, speeds in the hundreds of kilobits and megabits are very doable. I'll link a table below from 2015. Back then, megabit speeds were rare but I believe they're marginally more common now. Of course most people aren't hitting their nominal bandwidth amounts. https://www.klofas.com/comm-table/table.pdf https://www.klofas.com/comm-table/table.pdf

bsder 7y ago
And how will that TI chip work when hit with space radiation? And how far down the dbm sensitivity scale are those TI chips? You completely missed me pointing out that a cubesat-type project failed miserably for reasons relating to all this (Ah, found the link): https://hackaday.com/2020/01/24/lessons-learned-from-a-cubesat-postmortem/ https://hackaday.com/2020/01/24/lessons-learned-from-a-cubes... They call it "rocket science" for a reason.
- Rebelgecko 7y ago
  Not great, but it worked serviceably. Most of the chips going into LEO aren't rad hard. There's various techniques for dealing with problems like single event upsets and latchup. For the cubesat formfactor I think watchdogs timers are the most common and require the least overhead. I think this[1] is the datasheet for the chip that we used (on a custom PCB), I'm not an RF person but maybe that will answer your questions about dbs. Communication systems are certainly critical, and it's smart to have redundancy like that team did. However it's kinda like backing up your harddrive— redundancy is pointless if you never test it and it ends up not working. Lots of satellites have radio problems. Lots of satellites also don't have radio problems— there's always going to be a small number of random failures, but most of the problems are not insurmountable, especially if you're able to test extensively and iterate [1]: http://www.ti.com/lit/ds/symlink/cc1101.pdf http://www.ti.com/lit/ds/symlink/cc1101.pdf

bsder 7y ago

And how will that TI chip work when hit with space radiation? And how far down the dbm sensitivity scale are those TI chips? You completely missed me pointing out that a cubesat-type project failed miserably for reasons relating to all this (Ah, found the link): https://hackaday.com/2020/01/24/lessons-learned-from-a-cubesat-postmortem/ https://hackaday.com/2020/01/24/lessons-learned-from-a-cubes... They call it "rocket science" for a reason.

Rebelgecko 7y ago
Not great, but it worked serviceably. Most of the chips going into LEO aren't rad hard. There's various techniques for dealing with problems like single event upsets and latchup. For the cubesat formfactor I think watchdogs timers are the most common and require the least overhead. I think this[1] is the datasheet for the chip that we used (on a custom PCB), I'm not an RF person but maybe that will answer your questions about dbs. Communication systems are certainly critical, and it's smart to have redundancy like that team did. However it's kinda like backing up your harddrive— redundancy is pointless if you never test it and it ends up not working. Lots of satellites have radio problems. Lots of satellites also don't have radio problems— there's always going to be a small number of random failures, but most of the problems are not insurmountable, especially if you're able to test extensively and iterate [1]: http://www.ti.com/lit/ds/symlink/cc1101.pdf http://www.ti.com/lit/ds/symlink/cc1101.pdf