OGN-Airtracker

Live plane tracker based on Open Glider Network project.

Hardware

Hardware is a flavor of the Cheap Do-It-Yourself OGN tracker.

The latest version OGN-Airtracker assembly contains:

STM32F103C8T6 CPU board with ARM STM32 Cortex-M3 CPU @eBay
HOPERF RFM69HW transceiver @Anarduino
SMA-female socket with pigtail
50 ohm antenna with SMA-male right angle connector @AliExpress - see Antenna section below
adhesive copper foil tape for antenna counter-weight if needed as some of those short rubber/whip antennas are 1/4 wave monopoles and require ground plane for proper work) @eBay
VK2828U7G5LF GPS module @eBay
LCD for Nokia 5110 @eBay
18650 Li-Ion cell battery
Micro USB 18650 Lithium Battery Charging Board with undervoltage protection @eBay
18650 battery holder @eBay
Toggle on/on switch @eBay
Some female to female dupont jumper wire cables @eBay
Some toroidal ferrite rings for EMC filtering @eBay

Antenna

Disclaimer: First, I've to say, I'm an amateur in this field. Not a radio amateur, but real amateur. So some conclusions below can be pure nonsense.

I recommend look at really nice Understanding Antenna Specifications and Operation paper by Linx Technologies. Also ANTENNAS APPLICATIONS FOR RF MODULE by HOPERF is informative.

What I've learned:

1/4 wave antennas require ground plane to work correctly
- The ground plane's size and orientation has quite an influence on the antenna performace
- For example horizontal ground plane with antena orthogonally above will radiate above ground plane only (this is usually not wanted for things flying above groud-based receiver antenna - unless we turn the aircraft or at least the antenna upside down, but in this case air-to-air communication is still influenced)
For the best perfomance and the easiest installation the full dipole antenna is the best choice IMHO (of course vertically mounted for required polarization) and no copper foil into the case
I've bought a noname "10cm rubber antenna" thinking it will be better than those 1/4 wave antennas in a shorter housing.
* After removing the plastic housing, I've realized that it's just a 1/4 wave coil which could easily fit into a housing of a half length * So this antenna type would *require a good ground plane*
I've also bought "21cm 3dB antenna"
* This one has a whip style center-fed dipole antenna inside * Such antenna doesn't require a ground plane, moreover according to papers mentioned, the *ground plane can negatively influence antenna performace* (narrowing or widening bandwidth, shifting resonant frequency, increasing SWR, affect radiation pattern reflections)

Power supply

Approximate power consumptions:

STM32 max 50mA@72MHz
RFM69HW Tx 95mA/+17dBm
GPS max 67mW (20mA@3.3V)
LCD max 300uA
Total is cca max 165.3mA@3.3V

Regulator on STM32F103C8T6 CPU board:

DE=A1D - probably kind of RT9193-33:
Iout max 300mA
Vin 2.5 - 5.5V
dropout 220mV@300mA
low noise typ. 100uVRMS 10Hz - 100kHz @200mA
Avoiding other more or less noisy switching regulators, the integrated one should have enough power for all the peripherals and can be connected to 18650 battery (through an undervoltage battery protection circuit).