In article ,
"Meindert Sprang" wrote:

It's not the cable delay that counts in this case. The cable capacity is
important here and is used as part of the tuned circuit that drives the
transducer. If you change the cable length, you change the capacity of the
cable and therefore the resonance frequency of the tuned circuit. The result
is that the sounder cannot generate a sufficient high voltage to drive the
transducer.

Meindert

I hate to rain on your parade here Meindert, but most, if not all,
consumer Marine Depth Sounders, have Transformer Coupled outputs that
are resonate in and of themselves, and really don't care what is
connected to their output link as long as it isn't shorted.
The transducer is a Barium Titante Crystal that looks like a
capacitive load to the sounder transmitter, and if it isn't actually
connected, the few watts of transmitter power is just burned up in the
transformer as heat, as the average power is very low, similar to a
radars average power compared to it's Peak Power. Now if we are
talking commercial Depth Sounders, we are talking a horse of a bit
different color, but again operating them into an open transducer
line isn't very likely to cause any problems with the transmitter,
you just don't get any return. The result of all the above is that,
one "could" actually go and tune the transmitter for the best coupling
to the transducer connected, but the gain in signal/noise by doing so
isn't really significant. (Like less than 2db or so) The length of the
transducer cable isn't critical to the operation of the souder, and
many of these installations in the North Pacific Fleet have splices
in them due the cost of hauling the vessel to change transducers,
compared with just connecting a new sounder to what is already in the
hull. (Frequencys all being the same, between the old and new units)
There is Theory, and then there is 30 years of Practical........

Bruce in alaska
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