November 28, 2009
about 5 years ago
These are very finicky and very suspeptable to noise. In my opinion, not worth the headache over an Xbee. But if you really want to make use of these, you must do these two things:
1. Tune your antenna to the proper length. You can use this site to calculate a suitable length depending on frequency. (http://www.csgnetwork.com/freqwavelengthcalc.html). Full wave is most optimal, but ½ or ¼ is next best. You can experiment by adding/trimming length to the antennas. This will reduce your SWR. (http://en.wikipedia.org/wiki/Standing_wave_ratio)
2. Packetize your data and use checksums. On the receiving end, compute the checksum to make sure the data is clean before you “trust” it.
The device appears to do some adaptation, so if you send 10-15 “warm up” characters before the “real” data, this appears to improve the chances of the real data to be clean.
I get about 1200-1800 baud of usable data when using 4800 baud input at 40 feet indoors.
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