The scandal with the pingers is a big joke. The frequency (33.9Khz), it is close to 32.768 khz common frequency used in digital circuits for real timers that go off every second. Used by digital real time circuits for digital watches, computers, marine diving equipment.
I think someone posted they never identified that the pingers came from the plane. The protocol allows for the pinger detector to send a signal to get the aircraft id and air craft serial id number.
I got a big laugh when I saw them using a scope. You would think in this day and age it would be a device with an a/d convertor with DSP to recognize the ping and use the protocol.
With my knowledge & background, that’s what I’d expect, too.
I just don’t have exposure to these types of operations.
According to the manufacturer, Dukane Seacom, the frequency is 37.5kHz ± 1kHz. Nine milliseconds, approximately once per second. They also make a model that operates on 8.8kHz. They claim, "The lower frequency acoustic signature of the DK180 travels farther than existing ULDs thus improving locating efforts."
The protocol allows for the pinger detector to send a signal to get the aircraft id and air craft serial id number.
The data sheet makes no mention of encoding any information into the ping, although that would obviously be nice. But, really, how many sources of nine millisecond pings once a second on that frequency can there be in the South Indian Ocean?
I would think a two-way protocol would lengthen battery life by requiring the pinger to send only when it receives a poll from a search vessel. However, ensuring that the device can hear a poll reliably would be a challenge and an additional point of failure.
A two-way protocol would also allow a single search vessel to get ranges to the pinger from a number of different points, allowing its position to be determined. However, if there are multiple search vessels within range of a send-only beacon, they can compare ping arrival times and work out its location from that data, combined with their own positions at the time.