Ground Radio Unit

On the ground, size and weight considerations were not nearly as urgent, but sensitivity, power, ease of use and also the ability to also broadcast APRS information were.  This radio needed to be sensitive enough to communicate with a handheld radio that can be well over 50 miles away.  It also had to have a reliable power source and must be easy to use so that the ground team is able to concentrate on the road and not have to worry about interpreting data.  For the ground unit we have selected the Kenwood TM-D700A.  This is a very similar unit to the hand held THD-7 being that it also has a built-in TNC and built-in APRS software.  The TMD-700A is designed to take advantage of the car battery so that an external power source is not a concern.  It also has the ability to output 10 times more power and will be substantially more sensitive when listening for the balloon radio.  The TM-D700A is able to communicate with a laptop computer through a serial port; this allowed us to use software to overlay the information received onto a digital road map.