Yesterday I built the first complete PecanPico3 Tracker with a Si4464 transceiver chip. This is Serial #2. Serial #1 was only partially populated because I was hesitating to put an expensive GPS chip on the PCB without knowing if it works.I’ve had problems with PecanPico2 to couple the oscillator signal into the Si4464 and it turned out that I needed to attach the signal to the XOUT pin instead of the XIN pin. More experimenting showed that a 22 pF coupling capacitor is optimal for a stable operation of the Si4464. The theoretical value of 4 pF was too small and the PLL didn’t always lock to the correct frequency. However, this version of PecanPico3 seems to work fine just out of the box


Here are some example packets that can be seen on

2013-05-13 20:17:17 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:T#224,072,000,000,000,019,00000000
2013-05-13 20:17:30 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:/011506h2943.53N/09530.47WO000/000/A=-00179  3.8V 28C 101987Pa
2013-05-13 20:19:45 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:T#225,072,000,000,000,019,00000000
2013-05-13 20:19:58 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:/011732h2943.53N/09530.48WO000/000/A=-00179  3.8V 28C 101987Pa
2013-05-13 20:22:13 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:T#226,071,001,000,000,019,00000000
2013-05-13 20:22:26 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:/012001h2943.53N/09530.47WO000/000/A=-00181  3.8V 28C 101993Pa
2013-05-13 20:24:41 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:T#227,071,000,000,000,019,00000000
2013-05-13 20:24:54 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:/012232h2943.54N/09530.46WO046/016/A=-00181  3.8V 28C 101993Pa
2013-05-13 20:27:09 CDT: KT5TK-2>APECAN,WIDE2-1,qAR,KT5TK-6:T#228,073,001,000,000,019,00000000

The tracker is up on air for nearly 6 hours on a 400 mAh NiCd battery and still going. This made my decision easy for next Saturday where we’ll launch a 300 g balloon from our Fishfest QTH (Lake Livingston TX).  Pecan3 will fly!

Schematic: PecanPico3

Arduino Code:

Here is my parts list:

The uBlox MAX6Q GPS is available from HAB Supplies