How to Modifiy an ALPS BSJE3-159A Type tuner for ADSB
You can find this particular Tuner in a Technisat ST3002S but similar tuners are in many analog Satellite Receivers.
Three steps are needed:
- Disable AFC
- Adjust AGC via old AFC Pin
- Amplifiy and output 480 MHz after SAW on old Video Pin
Disable AFC by removing TA8754AF FM demodulator chip.
Remove coil on the left of the IC, the small component on the right and all components below the coil in the left.
Connect AGC to outside pin. Cut the PCB track to the pin on the upper side (see previous picture)
Add a GALI3 Amplifier:
Input 480 MHz from SAW transistor output.
Output via 100pF to Video Pin.
Output via 47 ohms to 5 volt power.
Note the GALI3
ground is soldered across 2 pins, the input on the bottom pin and the
output above pin. The next pin has 5 Volts, connect the resistor here.
The 100pF capacitor connects to the resistor on one side and floats in
the air on the other. A wire takes the signal to the Video output.
You now have a tuner for ADSB running only on 5 volts (For tuning at 1090 MHz is about 3.5 Volts) at around 300mA.
You can set the gain between min (0 volts) and max (4 volts) with a 10K voltage divider.
Front and Back side should now look like this: