Heavy rain affects Depth sounder and Fishfinder

[Simi 60]

Hi, Have an ongoing issue with sounders that I have never had on any other vessel I have owned.

Have two on this boat, a Koden near commercial quality full colour fishfinder and an ancient number only datamarine with a piercingly loud alarm.

Both transducers are mounted at least 6ft under hull yet whenever we get heavy rain both sounders lose bottom.

Any ideas?

[ozsailer]

Gday Simi,
I have not heard of this before. The only thing that I can possibly think of is that the frequency of the rain hitting the water is somehow interfering with the frequency that the transducer is set at. I am totally clutching at straws with this. Have you contacted the manufacturer to get their thoughts.



Greg H
Lagoon 440

[slug]

Originally Posted by Simi 60

Hi, Have an ongoing issue with sounders that I have never had on any other vessel I have owned.

Have two on this boat, a Koden near commercial quality full colour fishfinder and an ancient number only datamarine with a piercingly loud alarm.

Both transducers are mounted at least 6ft under hull yet whenever we get heavy rain both sounders lose bottom.

Any ideas?

Perhaps the rain makes noise when it hits the surface and your boat or installation magnifies this noise

[Uncle Bob]

Perhaps the rain, if it has been large downpour or for a long period has formed a layer on the top of the salt water with a transition where the two meet, somewhat like a thermocline, and the sounder is confused by this bouncing the signal off it and not the bottom.

[Simi 60]

Originally Posted by Uncle Bob

Perhaps the rain, if it has been large downpour or for a long period has formed a layer on the top of the salt water

Nope, happens within minutes, seconds even

Originally Posted by slug

Perhaps the rain makes noise when it hits the surface and your boat or installation magnifies this noise

Its a thought but being a heavy timber vessel you would think if anything it would deaden the noise

Originally Posted by ozsailer

Have you contacted the manufacturer to get their thoughts.

No, but flicking an email to Koden now.

As you know, we haven't had much rain here but the last few weeks have reminded me of the issue.
Storm on us, plenty wind and rain, knowing depth is pretty handy to have.

[Dsanduril]

Interesting stuff. The oceanographers use an acoustic rain gauge to measure rainfall at sea, turns out rain is quite noisy up to near the 50kHz range used by some transducers [edit - the image isn't showing the left scale, the top tick is 80dB, 10 dB/tick].



https://dosits.org/galleries/technol...ain-gauge-arg/

https://earthobservatory.nasa.gov/fe...ain/rain_3.php

[thinwater]

Originally Posted by Dsanduril

Interesting stuff. The oceanographers use an acoustic rain gauge to measure rainfall at sea, turns out rain is quite noisy up to near the 50kHz range used by some transducers [edit - the image isn't showing the left scale, the top tick is 80dB, 10 dB/tick].



https://dosits.org/galleries/technol...ain-gauge-arg/

https://earthobservatory.nasa.gov/fe...ain/rain_3.php

Exactly!


Can you change the transducer frequency? I do ultrasound, and that is frequently the cure when there is background machinery noise. Better sounders have two settings.

[Dsanduril]

Interesting thought (I know my basic units are 50/200kHz). Just grabbed a Koden spec for one unit:

Four selectable frequencies
This innovative sounder is equipped with the capability of selecting optional four frequencies within the range of broadband transducer (two types available: TDM-052 38kHz to 75kHz / 130kHz to 210kHz and TDM-062 38kHz to 75kHz / 85kHz to 135kHz). This feature provides its user with the possibility of fine tuning for spotting desired types of fish, improved search of water depth. Flexible selection of frequencies by 0.1kHz step enables the user to stay away from interference with the sounders on the other vessels.

Can you switch frequencies during rain and see if the higher frequency works better?

[Simi 60]

Will give it a try
It does have a 50/200 transducer.

[boat driver]

I this a new phenomenon or just at this location? Just wondering if the rain is noisy?
or if a creek nearby and with the dry conditions if sediment is arriving at the boat from rain ashore washinig down first.

[degouwb]

I also have two depth sounders, one forward and one the usual. On my boat both can't be running at the same time. I believe the echos interfere with one another.

[Cadence]

Originally Posted by Simi 60

Will give it a try
It does have a 50/200 transducer.

That was going to be my question. Does it occur on both freq. as I recall most sounders are 50/200. A really DAG wound be the rain is causing a harmonic.

[Simi 60]

I have always had the Koden running as split screen, one on 50 the other on 200 and it loses the numbers.
Not sure which freq the numbers come from, might need to read the manual (yawn)



Its really the ancient datamarine unit I am more annoyed about
That has the heart stopping piezo buzzer non stop screech on it instantly demanding attention to prevent ear drum bleeding.

The Koden in comparison has an easily missed quiet chirp and flashing icon like most fishfinders do.
Bloody useless as a warning device.



Datamarine pic found online but same unit as mine

[Cadence]

As a swag. Is it possible having both on is creating a problem?

[Simi 60]

Originally Posted by Cadence

As a swag. Is it possible having both on is creating a problem?

Nope, 1 on both on no difference.