The University of Nevada, Reno
Nevada Space Grant
Student
High-Altitude Ballooning

NV SGC
This program is generously supported by the Nevada Space Grant Consortium


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Secondary Communication Payload

Nevada is a very mountainous state and mountains block radio signals very well. The payload actually contains two backup tracking systems.  Both systems are designed to allow us to locate the payloads in the event we loose direct communication with the primary communication payload. This can happen when we loose direct line of sight with the payloads (HAM radio is largely limited by line of sight).

To compound matters, there is basically no cell phone coverage in rural Nevada. Thus, any technology that relies on cell phones will not function for most missions.

Current version of secondary communication payload

logomatic microtrak garmin

The secondary tracking system is a MicroTrak 300 radio, broadcasting on the national APRS frequency. It uses essentially the same technology as the primary communication payload. However, by broadcasting on the national frequency, we can lookup a history of locations online at FindU.com. Scattered across the US are thousands of HAM radio repeaters/gates which are set to the national APRS frequency. Thus, even though the chase vehicles may loose contact with the payloads, it is very likely that the payloads will still be in contact with a repeater/gate.

After several broken J-Pole antennas, we have switched back to using a standard Diamond SRH7CA dual band antenna. The J-Pole antennas worked great but had a bad tendency to break of immediately after the balloon burst (during post-burst-chaos). We theorize that the plastic used becomes brittle and them simply breaks off under the dynamic loading that occurs during descent.

The GPS in the secondary communication system also has a Sparkfun Logomatic data logger that records the GPS output to an SD memory card once every second (a Max232 chip is needed to convert RS323 to TTL). This provides us with the entire time history of the flight path (Lat., Long. and altitude). The MicroTrak radio, GPS, and data logger are all powered using an 8-pack of AA Energizer lithium batteries. The system will transmit for approximately 5 hours (the data logger uses the most power).

The secondary tracking system also contains a SPOT satellite personal tracker (not shown in photo above), a commercial product that can periodically report it's location via a satellite phone modem. The SPOT is used as a last-resort tracking option (i.e. the chase team cannot locate the payload using HAM radio). The SPOT device will transmit its location once every 10 minutes for 14 days (plenty of time to track down and recover the payload).

Previous version of secondary communication payload



The secondary communication payload is the bottommost payload (typically) because of the long J-Pole antenna used (now shown in the photo).

The first tracking system is a TinyTrak 300 radio, broadcasting on the national APRS frequency. It uses essentially the same technology as the primary communication payload. However, by broadcasting on the national frequency, we can lookup a history of locations online at FindU.com. Scattered across the US are thousands of HAM radio repeaters/gates which are set to the national APRS frequency. Thus, even though the chase vehicles may loose contact with the payloads, it is very likely that the payloads will still be in contact with a repeater/gate.

The second tracking system is a a PTT, better known as an "animal tracker," commonly used by scientists to track bears, whales, etc. Since the system is satellite based, it is not dependent on line of sight to either a chase vehicle or repeater/gate. Note: in the photo above, the gold colored battery is not installed. It normally would go in the large black cylinder. To date, we've only had to use the PTT once, but it saved the day.