Topic: what type interference is this

[mrrattle]

Hello everyone. this is a brand new unit. 798ci hd si
this is also my first post

anyway i have attached a very boring image.
on the bottom half of the image i was moving slowly, 3KM of so (trolling speed)
then on top half of image i throttle up main engine

anyway on the right side of centre line there is strong interference/return signal, that goes away when i throttle up.



hands up, how many think the interference at low speed is from my motor leg blocking part of the si view? (yes my transducer is on the left side of the hull)

and if it is the engine blocking the view, why does it clear up when i throttle up? this should put bottom of leg closer to hull and block more signal i would think.

and yet when i look across the back of my transom there is plenty of clearance.

[ITGEEK]

Interference is not caused by something blocking the
transducer.
It's caused from electricity flowing from one device, crossing/interrupting/vibrating
the electrical flow of another device.

Maybe at a certain main engine rpm, the voltage from your main motor
interfers the most with your sonar.

To permanently alleviate all of these issues, get yourself a small battery just for
your sonar.  Try and route the sonar wires away from your trolling motor and
main motor wires.  If wires have to go over other wires, do them at right angles
like a cross.

[mrrattle]

Wiring is already isolated-somewhat.

my transducer and power wires run down port side, all other wiring is on starboard.

this weekend i will be trying unit with a separate battery.

but it seems to me i still had the interference even when i had engine off

maybe it is coming from my am/fm radio that is located directly below the sonar control head.

[ITGEEK]

Could be.
I think trolling motor interference is the biggest complaint,
then main motor interference.
Try sonar with everything off, and just drifting.
Then try one electronic device, then shut off, then the next
to determine the culprit.

[Humminbird_Greg]

Welcome to the Side imaging Forums mrrattle.

I would also add a test with the boat drifting but the motor running out of gear.  Try revving the motor and see if the interference shows up again or not.

[mrrattle]

just an update, problem not solved yet but

separate battery installed-fixed an issue i had with recording stopping when ever I started main engine--interference persists.

main engine off and lifted out of water-still interference

every thing electrical in boat off (only a cheap radio), still interference.

but--i found that moving 3kmh or slower gives interference, above 3k the interference is gone.
boat drifting sideways to port-interference on right, boat drifting to starboard-right side interference reduced
I think it is turbulence off the transom.
I am going to lower the transducer and retest.

[abraquelebout]

hi
i get this type of noise in two things :

- using a bad electric converter (pc adapter, 12-220v or light (néon))

- noise on an aluminium hull (small wave hit the hull and must do this, changing direction resolve this)