Originally Posted by RR NDB
And the 2nd Solution at page 10:
Installation of low frequency ULB (between 8.5 and 9.5 kHz) attached to the plane
"Made my day"
All that for only doubling the range? The higher loss at 37.5kHz compared to the loss at 8.5-9.5 kHz is about what you get with slightly more than doubling your distance from the transducer.
A slightly different strategy might prove to be a winner. If you know the frequency within 1 Hz and it is transmitted continuously you can search with sub 1Hz FFT windows. That can purchase a good factor of 10 in detection range.
(Mumble mode) Continuous transmission at 1/100th power means you need a 1Hz bandwidth to get equal detectability for "very roughly" the same battery life. By then Dopper becomes a problem with a moving receiver. Oops! It seems there may not be a good strategy for improving detectability. But watching it on a waterfall spectrum display would allow one to eyeball finding it very nicely with 1Hz or slightly smaller windows.
{^_^}
{o.o}