"Rick" wrote in message
...
The cable should not be shortened at least that is what I was told. It
does not harm the unit to turn it on with out the transducer being
connected.

The transmitter sends a pulse of electromagnetic energy down the coax to the
transducer at the speed of light. The transducer converts that to sound
which travels at (yup) the speed of sound in water; then it listens for
echos and converts them back to electromagnetic signals sent via the same
cable to the receiver. The receiver measures the total time required by all
this to determine depth. If you cut 10' off the cable that determination
will be off by 2x the time required for a speed of light signal to do that
10'. Since the speed of light (186,000 miles PS IIRC) vs sound (about 1100
feet PS) that error is small.