Lion tracker comes with assembled PCB, soldered EMC shield and soldered battery.

How to get to antenna tuning circuit

Step 1: Desolder battery positive terminal

Step 2: Desolder battery negative terminal

Step 3: Desolder EMC shield

Preloaded SW on devices

1. LoRa_setTxContinuousWave_vswr

   - Frequency scan from 800MHz to 900MHz

2. LoRa_setTxContinuousWave_vswr_tune

   - DTC scan at 868MHz from 0 to 32 (1,4pF to 13,61)

How to activate device after battery soldering to Lion tracker

Every time battery is soldered to board a battery protection circuit needs to be activated.

Make contact from battery negative terminal to EMC shield to activate device.

How to read UART messages from device

Connect USB<->UART adapter to device pin as shown in picture above.

Schematic and PCB design

All design can be found on github

Schematic on bottom picture shows how is antenna wired with Murata IC and digital tunable capacitor PE64102 (DTC). DTC is wired in parallel with C7 to add capacitance and with that lower the antenna resonating frequency.

With recommended component values from datasheet we have antenna frequency that is far below 868MHz.

Frequency response with component values from datasheet shows frequency center at 785MHz which is 83MHz to low.

After tuning with capacitor on antenna band select pin we managed to get right frequency curve. Below on picture you can see frequency curve with different capacitor values with the most suitable 3pF capacitor.

Because the capacity is so small we can't fully use the potential of DTC. DTC has 32 possible combinations of capacity and we are operating at the beginning of this scale (at decimal number 4 witch is 2,98pF.

Can we make efficiency of antenna better when potted?