Comment by ErroneousBosh
11 hours ago
Why do they do WSPR on HF and not 2.4GHz?
What's the important part that defines what kind of range you can get?
11 hours ago
Why do they do WSPR on HF and not 2.4GHz?
What's the important part that defines what kind of range you can get?
WSPR on HF makes sense down here on the surface of the planet because certain ranges of frequencies (not the same range always, but generally always within HF) can bounce off of upper atmosphere layers and pinball back and forth to get signals to someone or from someone who couldn't be seen line-of-sight because of the curvature of the Earth. For line of sight work, the 2.4GHz in theory would work as well as anything, but another trick WSPR has is that it doesn't allow for arbitrary data to be sent. Sender and receiver encode the limited information in an agreed-upon way and then it takes a long time, like minutes, to send that little bit of data. Very high redundancy.
Yeah, our baloon was recorded by WSPR eeceivers thousands of kilometers away when it crossed the arctic circle for a day - we wpuld have no data if it were dependent on line of sight or even just flying over inhabited territory.
And indeed, the relions take minures to send a couple dozen bits of data. But the modulation is done in such a clever way, that it does not really matter - you know ehere the probe with your callsign was, how high, ground speed, temperature and panel volatage. There is quite agressive heuristics applied (eg. different precision for different altitudes as you don't really expect it to stay low for any ammount of time and survive, position via grid squares with course position still available even if you have incomplete data from a relation) so the few dozen bits are enough. :)
It is all super clever and hats off for those who developed this system. :)
You know that and I know that, it was a Socratic question aimed at OP ;-)
In the olden days we did QRSS, FSK Morse with a dot rate in the order of minutes.