In article ,
"Lynn Coffelt" wrote:


Bruce, weren't all FCV-261's dual frequency? I recall them being
available in 28, 50, 88 or 200 khz combinations. This big daddy (for it's
day) actually had two separate transmitter circuit boards it seems, and the
output connectors were separate for two transducers. (two single frequency
transducers, that it) rather than the single, dual frequency transmitter
with a single dual frequency transducer, as many (most?) of the smaller,
lower cost models.

They had display switching to show either of the two frequency echoes
or the echoes of both frequencies superimposed. (or maybe memory isn't too
sharp). If I'm not completely looped, when the rig was switched to display a
single frequency, the unused TX/RX board was not driven. Do you remember
anything like that? I think some of our "black cod" longliners just used one
big hooter of a 28 khz transducer in a tank with that 261. (sometimes the
transducer was from an older Furuno paper machine that was eating up too
much $35 a roll 8" paper)
It was good to find out which power switch was the correct one for low
power when using a small transducer with a Furuno 1kw machine, as they can
easily damage the little plastic "100 watt" Radarsonics, Gemtronics, etc.
Some of the little low power transducers with a rubber face would stand a
little extra power if they were run in the water (not "tested" in air).
Something about load matching??

Oh, gosh, the original poster's question! If it was me, I'd put a 100
watt (120 volt) lamp across the transducer connections for a load and run
the rig briefly (real briefly) in a dead quiet location, and you can easily
hear the transmitter thumping. Quickly run the switch through the four
settings and you can easily tell the high and low power settings. And mark
position clearly! Or, if the transducer is already installed, and that's
the name of the game, just get to dead silence again and have someone
stationed inside the boat right at the transducer, and listen. The 1kw pulse
will be clearly audible (snap, snap, snap)
Maybe don't make those last tests if you've been working over a
hammering "Jimmy" most of the day.

Old Chief Lynn



The Old Gray Matter isn't pinging like it used to, and it has been a few
years since I was actively dealing with these things, so that's why I am
not sure what the spec's on the unit in question, are. I am mostly
ReTired with an emphisis on TIRED, these days but the principals are the
same, and the advice is sound, even if the rest of me isn't all that
sound.......

Bruce in alaska
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add a 2 before @