Tuesday, September 21, 2010

XBee Repeater

I am finally ready to perform some long-range XBee testing using the Digi XBee-Pro XSC modules. I put together a few simple Xbee repeaters utilizing an Xbee-Pro XSC 900Mhz module, a simple rs232 interface, and power supply. Power come from a pair of 18650 lithium batteries.

I made two of the devices above as they are useful for any project that needs portable XBee communication. Simply hook any two laptops or mobile embedded devices up to the pair via rs232 and you have instant point to point mobile serial communication. To enable the device as a repeater, I made a loopback device that plugs into the serial port echoing anything that arrives on the serial rx line back over tx.

The simple 900mhz antenna hooked up to it works well for testing, but I have a pair of high gain 900Mhz ISM band yagis I plan to use for long range testing.

These yagis connected to the Xbee PROs with good lmr-200 cable should make for some very long range communication. The biggest issue is finding a good line-of-site location to test. I have been studying some topographical maps around the Ann Arbor area trying to find two good points of high ground, or a point from a tall structure to high ground. So far I have some good tests at about 6 to 7 miles (which doesn't seem like much, but when trying to see from your point on the ground is a very long distance away). Standing at ground level (if at sea level and looking out), from your eye level (say six feet up) you can only see about 3 miles to the visible horizon. Increasing your distance above the earth to 100 feet only increases the visible horizon to about 12 miles. So I will need to find some tall structures or high ground to test the full 15 mile range that the Xbee datasheet states for the maximum range.


  1. I'm champing at the bit for you to do the long-range XBee testing. Do tell when you have some results!

  2. Hello I am also working on a similar project with Yagi's and Xbee S3B. Looking to get a good signal at about 16 miles from a 12 story building. Did you ever finish the project? I'd like to hear about it. Thanks!