Odd sounder issue

[jokaboat]

On Sunday as we were leaving the Itchen heading out into Southampton Water, just past Ocean village our through hull depth sounder went gaga, reading all sorts of depths, followed shortly by the depth readout on out plotter/fishfinder doing the same.

We were being very good and sticking to the 6 knot limit.

Rats I thought, picked up a plastic bag or something.

Anyway I stopped, reversed, went round in a circle but no joy so we carried on.

As we cleared the Calshot Channel marker, at the point where you can change from pootling along to yee hah speeds both sounders returned to normal operation and stayed that way until we returned to the same spot where it all kicked off again.

As we passed Ocean Village going upstream both sounders again returned to notmal operations.

The only thing I can think of is that the mega car transporter that was in the vicinity was utilising some underwater kit that was interfering with the transponders.

Weird.

[Cap'n Jack]

Fascinating.....no idea though!

Sometimes these things go a bit doolally if there is a reflection from just below the hull when it can't give a reading because its not calibrated to very low levels, but thats unlikely.

Just a thought, does this happen at certain revs and maybe the place it happens is a decoy?

If it was the transporter it would have to have massive power to interfere at distance. Still only guessing though, we are talking about sound waves at (I think) 75-150khz ish.

[jokaboat]

We were around 50m from the ship in about 12m water. Odd that is was OK either side.

Next time we go out I'll try to hit the same spot and see if it happens again.

[Cap'n Jack]

Could be that it was transmitting something.

[BIG ZEBEDEE]

Sounds like Nessie is taking a holiday on the south coast
Sorry

[jokaboat]

Sounds like Nessie is taking a holiday on the south coast
Sorry

Well she's entitles to a holiday occasionally. Why not head south to .warmer waters.

[jokaboat]

Could be that it was transmitting something.

I wondered about forward or side scanning sonar? Or is it a secret spy ship

[Cap'n Jack]

Arrrrrr!!!

It's that black stealth boat at Saxon.....

Actually, was it opposite the Harbour Masters place? There is also a Vessel Traffic Services Centre there, checked on Navionics this morning. I wonder if they have something which interfere's going on.

[jokaboat]

Well there we were yeaterday , same spot and guess what, the through hull sounder started whinging that there was no depth, completely lost it's reading. The fish finder carried on OK this time though. We were in 7m of water and no sign of floating stuff in the water that might have blocked the transducer.

Again there was a car transported on the berth.

Coming back in it didn't happen although we were further off towards the other side of the channel.

We did lose signal a couple of times coming up Southampton Water but we were airborne at the time

Weird.

[Ed]

I must admit I find issued at WOT with my sounder.. No idea why!

[Cap'n Jack]

Thats because you drive something resembling Bluebird the speeds you go!!!

[dpb101]

At high speed you can get air bubbles under the hull, especially if you're getting the hull out of the water at all.
The depth readings go back to normal when you slow down and the air disipates

[Ed]

Lol yes sorry, I was being sarcastic. I guess easily missed on a forum Its not unusual apparently for almost nothing but my prop to be touching the water lol, sometimes that doesn't either haha.