We are launching a weather balloon and we are going to track it using the Xtend modules.
We are doing some range testing on monday, but I want to work this out before we test:
What is the best baud rate for long range comms, and does it even matter?
The Xtend modules only send out a transmission when the buffer is full or when there is no further data on the input, so the question is, does the Xtend module really change its transmission speed, or is it always transmitting at the same speed, and only changing the baud rate of the TX and RX pins locally as necessary?
I mean, it receives the serial string into its internal buffer, then sends it through its own format then converts it back to the appropriate baudrate at the receiver right?
If so, it would not really matter what we set the baud rate to… since the transmission is the same regardless?
I mean, it receives the serial string into its internal buffer, then sends it through its own format then converts it back to the appropriate baudrate at the receiver right?
If so, it would not really matter what we set the baud rate to… since the transmission is the same regardless?
Correct.
There have been a number of threads asking the same thing you do about range from a balloon. Search these forums to find the treads.
Just a thought, I’ve seen 2+ mile range out of XBee Pros with the right antennas, 60mW TX power. Plus, that is at 2.4GHz. Pick the right antennas and you’ll maximize your range.
Also, like mentioned before, baud doesn’t matter. They use a set frequency to communicate wirelessly that you cannot change.
Line of sight and no multipath reflection is your best friend! Us land dwellers get lousy reception point to point, due to multipath bounce of the signal we want. Due to the noncoherent mixing of the signal, you can lose 20 to 30 dB of signal strength just moving a couple of inches one way or another! In space,you can easily get a few kilometers with 10 mW. A watt with a slow data rate should get you a hundred kilometers from space. LEO satellites are 400 miles? up, and you can hit them with a couple of watts at 1.7GHz. A directional antenna pointed straight up is all you need on the receiving end. A patch antenna pointing down from your balloon, and you may even be able to up the data rate to send live video! or more realistically, 100K or so.
Do a search for IBCrazy clover leaf. You can make a cheap circularly polarized antenna that has a good radiation pattern and good multipath rejection when paired with a similarly polarized directional antenna.