AF 447 Search to resume (part2)

[RR_NDB]

ULB detection

With this 1% duty cycle (specified for battery life), very probably:

1) They used RC oscillator (frequency dependent on batt. voltage) at TX
2) Peak detector at RX
3) Conventional RX front end BPF (not a very sharp one)

Conclusion:

Clearly there is room for improvement for much better ULB systems than the current std.

PS

The DSP examples i presented are not "well suited" to "short pulses" (short ones compared to the pulse repetition period).

The DSP technique probably was the one allowing Orion P3 based in Moffet Field, locate through sonobuoys the USSR subs in Pacific ocean. The sub propeller shaft generates a continuous "signal" allowing a good RX S/N ratio through DSP. The Orion as a signal repeater to remote powerful computers.

Mac