Distance Testing the NXTBee

A NXTBee with Digi's Latest Radio

We recently wanted to distance test the NXTBee.  In this post, we review some of the distance results of testing the distance of the NXTBee XBee radios for LEGO MINDSTORMS.

The NXTBee has some major advantages over the Bluetooth module found on the LEGO MINDSTORMS NXT.  The advantages include:

• Mesh Networking (great for swarm robotics!)
• Data Verification.
• And last but not least: Long distance communication.

Digi, the manufacturer of the XBee radio behind the NXTBee recently changed the antennas on the radios we buy.  The old XBees had a chip antenna on them while the new Xbees have an antenna that’s a PCB trace.  We were curious if this affected distance performance.

The good folks at Robomatter were kind enough to test them (Thanks John!) for distance performance a few days ago.  John did 8 tests in the real world.  Unlike the certification given by Digi these tests were conducted in the real world, with the LEGO MINDSTORMS NXT, interference from other radios, people walking in between the Xbee radios, and the other problems you would see in the real world.

Two types of radios were tested:

• Chip radios (the old version shipped with the NXTBee pre-2012).

• Trace antennas (the new version shipped with NXTBees sold in 2012).

Chip Antenna Xbee Radio (old)

XBee with Trace Antenna (NEW)

The results are pasted below.  The new trace-antennas show improved performance to the old XBee chip-antennas.  The chip-antennas showed an average of 198 feet before dropping off while the new trace antennas boasted an extra 16 feet of range, reaching .

• On-chip ranges:  216ft, 216ft, 192ft, 168ft (Avg. of 198 feet, rounded to 200ft)
• Trace ranges: 216 ft, 216ft, 216ft, 216ft (Avg of 216, rounded to 220ft)

The stated ranges of the radios, by Digi, are:

• Digi Stated Range: Indoor/Urban Range 100 ft (30 m)
• Digi Stated Outdoor/RF Line-of-Sight Range 300 ft (100 m)

The performance of the different antennas will vary depending on how you’re using them.  For example, if you’re outside and the radios can see each other (called line of sight), they will perform better.  If you’re in a crowded area or there are a lot of walls between the radios, the performance will be lowered as well.

Bottom-line: if your XBee looks a little different than the pictures we show on our website and has a trace antenna, you’ve bought a slightly improved product!