Originally Posted by
Niner Lima Charlie
It was reported in Perth that the Australian Navy "Ocean Shield" detected the first signal and tracked it for two hours and 20 minutes. Then turned around and tracked a second signal for 13 minutes. These pings were on 33.3 KHz rather than 37.5 KHz, which the pinger manufacturer says would account for drift due to low battery after 30 days active.
I find it extraordinary that the ping frequency apparently changes so dramatically with power supply voltage! Surely the device is crystal controlled? what use is a device like this if the frequency one is looking at is effectively unknown. To detect the signal at a distance one needs to use very narrow bandwidth filters of the order of only a few Hertz: here we are talking about a shift of 4.2KHz, well over 10%...
I don't believe this equipment performs this badly, given it's designed role. was the Ocean Shield following something else? can someone quote the source of the "manufacturer's" comments?