Problems with Uplink

[Austin MnSGC]

We had a flight on Tuesday, June 21st, and we decided to try setting up our tracking station downrange of where we released the balloon from to see if we could get better signal during the peak of the flight. This actually worked very well, and we were able to receive transmissions from the flight unit through our ground station for pretty much the whole flight, only really losing it when it was very close the ground.

However, the flight unit never received any of our transmissions to it. After checking the runtime data on the Pi, it looks like nothing sent from the ground station to the flight unit was received once it was at a high altitude. We're using the normal yagi and patch setup on the servos on the ground, and in our flight unit we have the two quarter wave antennas at right angles with each other along with the metal ground plane.

Do you think we need larger/better antennas in our flight unit in order to let it receive things from our ground station?

[David MSGC]

Sending commands to the payload are just one ascii character which is one byte and is typically limited by line of sight once beyond a few miles and can be received by the payload from over 60 miles. Usually when the payload does not receive the command it is something not turned on or hooked up, ie python program not running on the pi or an antenna not connected properly. If this happens the first thing to check is if the radios have connection, look at the green led on the radio, if it is solid it is connected to the other radio, if it is blinking it is searching for radios and not connected. If the led is solid, the program on the pi is running then I would make sure the radios are configured properly which cannot be done during flight.
Note: if you experiment with the code the command being sent needs to be just one character or you will have to edit the serial read to accommodate more than one character and the logic for deciding what command was received would have to be changed to a string. Sending a string instead of a char will reduce the range and reliability.

[David MSGC]

Just an update for future reference: It has been found some radios are only transmitting at half power or the receiving radio is receiving half the signal strength. So far this has been due to damaged radios by not having an antenna connected before powering up the radio.
ALWAYS have at least one antenna, preferably two antennas, connected BEFORE connecting the FTDI cable. As soon as the cable is connected the radio is powered and the radio will start transmitting looking for another radio to connect to, if there is no antenna attached there is a good chance of damaging the radio.