sounder & VHF

[the baker]

hey all I have a small problem the sounder interferes with the VHF any ideas as what may cause this I can hear the trany ticking away through the radio

[Noelm]

check the cabling, especially the antenna for the VHF, then the power wires.

[Defore]

Is the wire for the transducer running along side the wire for the antenna?
Best to have these separated.

[the baker]

Is the wire for the transducer running along side the wire for the antenna?
Best to have these separated.

Yeah I have them separated

[the baker]

check the cabling, especially the antenna for the VHF, then the power wires.

doing that now, so I will see how it go's

[oldboot]

HOW seperated?

remember even the cheaper sounders output about 200watts peak to peak and the wave shape is pretty nasty and high frequency.....The tick you hear is actually a burst of high frequency......

you real should have your sounder cable and the radio coax well seperated.

Yeh I supose there is a posibilty of it comming thru the power supply........ but direct radiation is a better bet.

cheers

[Sea-Dog]

I had a similar problem: Whenever I turned on the sounder, I would have to increase the squelch level on the VHF due to interference.

I was able to cure it by wrapping both antenna cable and sounder cables individually in aluminium foil.

It worked well for a while, but the alfoil eventually loosened and looked crap, so I removed it.

I must do something more permanent about shielding soon.

Try it yourself - Alfoil doesn't cost much to see if shielding is needed. If the alfoil cuts down the interference, then look for something a bit more elegant to do the shielding with.

[Defore]

I had a similar problem: Whenever I turned on the sounder, I would have to increase the squelch level on the VHF due to interference.

I was able to cure it by wrapping both antenna cable and sounder cables individually in aluminium foil.

It worked well for a while, but the alfoil eventually loosened and looked crap, so I removed it.

I must do something more permanent about shielding soon.

Try it yourself - Alfoil doesn't cost much to see if shielding is needed. If the alfoil cuts down the interference, then look for something a bit more elegant to do the shielding with.

Aluminium tubing will do the same thing, should only have to put one of the cable inside the tubing. Probably the Sounder cable.

[oldboot]

Seadog...as a matter of interest, how where the cables run, how far appart and how much did you wrap in foil.

The radio coax will have a braided copper shield will attould 70-80% braid coverage.
The effectiveness of this shiled will vary with frequency.....but yep it aint 100%

The sounder cable is anybodies guess... it may have no shiled or a foil inside the jacket.

These days in decent TV coax they run 4 shields ( 2 braids and 2 foils) to make the shilelding as good as it can be.

But shielding only provides isolation against electrostatic noise ( unless it is iron or steel).......so running cables side by side even with the best shielding can be an issue...inductive coupling will still occur

So adding better shielding may be a real option where the cables are close....but being a marine thing corrosion will be an issue..........the aluminium tube may be an option.

If it was only a short distance, stripping the foil and mylar tape out of some other cable and using that may be an option...either tape it over or heatshrink it.

remember for shielding to be most effective it needs to be bonded to "earth" or negative at least at 1 point.

another option if the cables must run together..it to try and get one either side of some sort of metal seperator....say run one in a channel and the other outside...or either side of a metal divider that just happens to be there.

there are flexible metal conduits out there, or you could use a plastic tube and spray it with shileding spray... but we are starting to get exotic here

Good seperation will always beat shileding

cheers

[the baker]

WOW you bloke's have some good info thanks heaps to you all.... Awesome

Dave.

[Sea-Dog]

Seadog...as a matter of interest, how where the cables run, how far appart and how much did you wrap in foil...
cheers

Hey 'boot,

My boat is an open tinnie, so everything is mounted under the gunwales on starboard side. VHF, Sounder/GPS combo, Switchboard etc, as well as the 2.4M antenna.

Not much space available to separate things.

I wrapped the antenna cable from the back of the radio (not touching the plug) all the way to the base mount of the antenna.

The GPS/Sounder leads, I covered from where the leads go through the side deck about a foot forward of the conglomeration of coils and aft to the stern.

I do have my external GPS antenna mounted on the Port quarter.

To keep the extra cable lengths tidy, I have them coiled - that may create a bit of an inductive loop that sends signals from sounder/gps leads to VHF antenna cable (also coiled).

I don't know if I could fit a coil of cable inside an ally tube, but its certainly worth considering.

Sometimes I wonder what messages I don't hear on the VHF due to having the squelch turned up another quarter of a turn.

I don't like to turn off the sounder, as I like to keep track of my movements on GPS.

I think I'll do some scrounging around for a bit of ally tubing of a decent diameter - 25mm ID.

Cheers, Ross.

[oldboot]

in a tinny you can try and run the sounder cable down the oposite gunwal..if its front steer.
Or if it tiller run the aerial cable forward

or run one of them in the gunwal and the other under the floor or along the inside of the chine.

at the frequencies we ar talking about I doubt the coil would be doing much unless they were looped up together.

I've never tried to buy mylar foil tape, but I have seen the stuff and recon it could be had

If its tiller steer and it isn't far to run.....the cheapes source of alloy tube I have seen is by buying a cheap boat hook or paddle and pulling the ends off.

Unless you can find a disused lylo and have at it with a hacksaw.

cheers

[Sea-Dog]

in a tinny you can try and run the sounder cable down the oposite gunwal..if its front steer.
Or if it tiller run the aerial cable forward

or run one of them in the gunwal and the other under the floor or along the inside of the chine.

at the frequencies we ar talking about I doubt the coil would be doing much unless they were looped up together.

I've never tried to buy mylar foil tape, but I have seen the stuff and recon it could be had

If its tiller steer and it isn't far to run.....the cheapes source of alloy tube I have seen is by buying a cheap boat hook or paddle and pulling the ends off.

Unless you can find a disused lylo and have at it with a hacksaw.

cheers

My boat is a tiller steer until I get around to "centre consoling" her, so can only really route the wiring where it is.

Yes the coils of wire both reside behind a plate mounted between two ribs. My radio is mounted on that plate.

The Sounder/GPS sits just a whisker forward of that on top of the gunwale.

As far as the suggestions go...

I just remembered that I threw out the ALLY frame from an old bimini around a month ago after it sat in my shed for a couple of years. - DOH !!!

I like the idea of the disused furniture tubing though.

Now when's the next hard rubbish collection?

Cheers