I am a member of the University of Minnesota CanSat team. We compete in an international competition that requires us to launch a payload in a rocket to about 2200 ft. As the payload descends, we need to collect telemetry data streamed to a ground station. Currently, we use Xbee Pro S1’s for our data transmission and communications. The sensor system includes an Arduino Pro Mini micro controller, a barometer (BMP), an accelerometer (MMA), a real time clock, and an OpenLog data logger. The data transmission is a comma separated value string sent through the serial connection on the Arduino.
We are running into some issues with the range of our Xbees. First, we haven’t been able to achieve the full range yet. This may be due to testing them in the city. Although, we are trying to test in areas with good line of sight. This is the issue we have been trying to debug the most intensively. In range tests, we have only been able to transmit and receive data over a distance of 1,100 ft.
One of our ideas to remedy this was to measure the current draw of the transmitting Xbee. We did this by connecting a DMM in series with the 5V pin on our breakout board (WRL-11373) and our unregulated voltage source (a 9V battery). We measured a steady current of about 60 mA with bursts of 70-85 mA. This puzzled us because the transmitting current of the Pro S1s is supposed to be 215 mA. Are the bursts so short that we cannot see them on the DMM, or is our Xbee actually only drawing a max of 80mA during transmission? We have verified through the XCTU software that both Xbees are set to the high power level (parameter PL=4). Are there any settings that have to do with retries or other settings that could improve our range?
Are there any issues with our setup, or do you see any other ways we can improve our range?