Not a pinger
The 1.1 second pulse rate and the frequency sound about like a hydrographic sonar system I worked on designing back in the late sixties. At 4800 feet per second in water and a two way path that is appropriate for depths of 2500 feet. The pulse width we used was in the 5 to 25 millisecond range depending in part on the bottom material which has varying reflectance qualities at 33 KHz.
But that range limitation is only if you only have one pulse in the water at a time. For the higher range sonar chart recorders we could have 8 or 10 pulses in the water at a time. The chart and some memory let us focus on the bottom profile so the multiple return echos were easy enough to identify... if you did a few 1 pulse soundings to get the bottom range. Something like the old Omega nav system: you had to know where you were to get started.
Our sonar output used a very large transducer to help focus the signal. But not too narrow a beam because of survey vessel roll. With 500 to 2000 watts into a good transducer the range to a sensitive receiver would be very long. Certainly many miles. The signals heard may have been an echo off the bottom.
The reported frequency of the pings sounded much too low and that deviation from spec was apparently considered a possible consequence of low battery voltage. But maybe the frequency did not go down further. I would be very surprised that the resonator could go more than 2-3 KHz off the centre frequency due to dropping battery voltage.
I would hope someone obtained an identical pinger and measured the output frequency with decreasing battery voltage.
Last edited by ve7pnl; 29th May 2014 at 22:20.
Reason: typo: pulse width, not rate