Depth Sounder question/idea

[quilbilly]

Because my boat has a pilot house that I use a lot I can't see the depth sounder where it is mounted in the cockpit from inside. I considered trying to move it so I could see it but there isn't a particularily good place. I played around trying to put it inside the pilot house where I could look at it from outside through a window but with all the glare from the glass it is hard to see. Plus it would be in the way. I know I can get a repeater for more expensive sounders but the price gets pretty high as near as I can tell to replace everything. So I was thinking about getting a second one like the one I have, it is a Garmin FIshfinder, less than $100, and having a selector switch for the transducer. There are only three wires in the tranducer cord so it would take a triple pole double throw switch if such a thing exists. So my questions are: does anyone know what the three leads do and is this a workable idea?- Thanks Todd

[Frosty]

Why not just buy a second system. If your boat is fibre glass you dont need to cut a hole in the boat any more.

I did just this ,--one hummingbird for the bridge and a serious ( for bad weather) Navman for down stairs . I fire both transducers through the hull and they are sited 8 inches apart from each other without affecting each other.

[quilbilly]

I have thought of a second sounder and shooting it though the hull but my boat is plywood and it would need a fairing block as well to get the tranducer to point down. I have thought of a transome mount for a second sounder but I am curious if there would be a problem using one tranducer and switching it. Thanks Todd

[TerryKing]

Originally Posted by quilbilly

..snip..I am curious if there would be a problem using one tranducer and switching it. Thanks Todd

Todd, if transducers can be plugged and unplugged they can be switched..

Try to find out the cable characteristics.. Is there a shield? Look at the connection diagram if you have one. It may be that there are really only two 'active' connections and one common connection that may not need to be switched. If so, a conventional double-pole double-throw switch may be enough. 3 and 4 pole switches do exist but are less common. An alternative is a rotary switch; these come with many different poles and 'throws'.

I don't think this will be a big problem as long as the switch location is well protected against moisture.

[Frosty]

I once temporarliy fitted a cheapo to a boat by fitting it to the swim platform. The thing is I was rough with it --I cut the wire and just twisted in some 220V lighting flex,---it worked fine with no noticable loss in performance.

There is only 2 wires and a sheath. I didnt bother with the sheath.

I have posted this before with cries of Oh it wouldnt work-- You would have reduced performance.

I dont think you will have trouble switching. One thing you must take notice of is depth sounders come in different frequencies.

[Poida]

When you switch try to keep the length of cable the same from the switch to the sounder.

Sheathing is to protect the signal from residual electric fields and is a bigger problem with AC so generally an unsheathed cable would work in a DC boat.

Magnetism could effect it, so keep any unsheathed bits ie the switch away from things like a compass.

I've only worked with Co-Ax in stallite TV and I have have no experience with sounders but I would assume 1 cable takes power to the transducer, 2nd would take the signal to the transducer and the 3rd would return the signal.

The unit reckons the depth by timing the difference between the signals. Any unit you place in line that either speeds up the signal ie reduces the resistance or slows it down alters the reading from the true value.

The difference may not be significant.

Poida