RONJA

The device consists of a receiver and transmitter pipe (optical head) mounted on a sturdy adjustable holder.

[6] Several techniques – drilling templates,[7] detailed checks after soldering,[8][9][10][11] testing procedures[12][13][14] – are employed to minimize errors at critical places and help to speed up work.

[15][16] People with no previous experience with building electronics have reported on the mailing list that the device ran on the first try.

[2] With the brightest variant of Lumileds HPWT-BD00-F4000 LED and 130 mm diameter cheap magnifying glass lenses, the range is 1.4 km (0.87 mi).

The usual approach in FSO (Free Space Optics) preamplifiers is to employ a transimpedance amplifier.

Operation in a usual circuit with current drive would lead to substantial signal corruption and range reduction.

Therefore, the nominally digital[31] 74AC04 is operating as a structured power CMOS switch completely in analog mode.

This way the LED junction is flooded and cleared of carriers as quickly as possible, basically by short circuit discharge.

The side effects of this brutal driving technique are: 1) the LED overshoots at the beginning of longer (5 MHz/1 MHz) impulses to about 2x brightness.

2) A blocking ceramic capacitor bank backing up the 74AC04 switching array is crucial for correct operation, because charging and discharging the LED is done by short circuit.

Ronja Twister is an electronic interface for free space optical datalink based on counter and shift register chips.

[33] Soderberg, studying Ronja sociologically, writes: "Arguably, the first project that vindicated the methods and licensing schemes of free software development, applied those practices to open hardware development, and pulled off a state-of-the-art technology without any backing from universities or firms, was the Ronja project.