Mosquito1 — The 2m Version of the HabAmp

VK5QI has designed a legendary low noise preamplifier for HAB tracking. M0UPU has improved it and sells them in his HAB Supplies shop for a very reasonable price. However here in the US balloon tracking mainly happens on APRS in the 2 m band. Unfortunately there are just a very few SAW filters available at this frequency and of course they have a completely different footprint. Therefore it was necessary to design a new PCB in order to build one for the 2 m range. The result of this 2 m version can be seen in the pictures below. As usual I gave it a name that’s typical for Texas: “Mosquito”. I was stitched several times through the design phase an I thought it was an appropriate name considering the almost inaudible high pitch tone a mosquito makes while in the descent phase before landing.

The SAW filter TriQuint Semiconductor 856929 is available from Mouser and I ordered twenty PSA4-5043+ amplifiers directly from Mini-Circuits. The ferrite beads were replaced with TDK MPZ2012S102A (Mouser).

I’ve pushed the Eagle files to my GitHub: https://github.com/tkrahn/mosquito

The Mosquito1 amplifier seems to perform great with a RTL-SDR but I haven’t made any serious measurements yet.

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PecanPico3

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

PecanPico3

Here are some example packets that can be seen on aprs.fi:

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 http://tkrahn.net
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 http://tkrahn.net
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 http://tkrahn.net
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 http://tkrahn.net
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: https://github.com/tkrahn/PecanPico

Here is my parts list: http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=33053ee4fd

The uBlox MAX6Q GPS is available from HAB Supplies