997 noise snapshots

[Cane Pole]

Running Big Engine only trolling.



Big Engine only at idle.



Garmin 240 interference only.




Engine off and Garmin 240 off = clear.



Again, let me repeat. the 997 has it's own battery.

I realize the 240 can interfere with the 997, but it interferes only in the SI mode.

The Humminbird transducer is not on the step, it is on the hull to the right and forward of the prop by greater than the mentioned 15 inches. It is underwater at all times, but it looses bottom contact at above 30 mph. Again, it is not mounted on the step.

I will get it fixed. I am just sharing this info. I am pretty sure it is cable crosstalk.

Not that important, just aggravating. We don't turn the unit on when fishing. Got a 240 on the bow that does just fine (and my laptop if need be).

Also, turn filer on will remove snow, however, that would be like paying for HDTV and receiving analog (Defeats the purpose) and filters reduce reception definition. Period.

[WarrenMN]

The first one is likely cause he has a deep Vee hull. Picture digging a notch in wet sand at a beach. Thats what the water going under a deep Vee hull boat does when its on plane. The transducers aren't usually mounted at the deepest part of the hull so they're off to the side of this valley. Sonar doesn't like air and thats what this V notch is doing. Even coming off plane the boat is going to leave a lot of turbulence and air bubbles in this valley, causing a lot of attenuation until the water has time to settle down.
The second one I'd guess is ignition noise. Try an AM radio back by the motor when its running and see if you get a lot of RFI. Thats not going to matter what battery its hooked to. The best thing there is to shield it some how. Simple aluminum foil around the cable "and grounded" would be a good test.
I don't think the third one has any interference which surprised me, if the other sonar was running. The person that recorded this likely had the boat in motion and shut the motor off which caused the boat to slow way down. Half a MPH is going to be just short of not moving at all and thats only going to give you lines from top to bottom cause nothing is changing. In this case hardly any thing is changing. Thats why any object will become elongated top to bottom. Any thing short of a butt smooth bottom will look like lines. He could set the chart speed to 1 to try and improve the view.
The last one is just the same as the one above, .3 mph is worse.

Warren

[Cane Pole]

The first one is likely cause he has a deep Vee hull. Picture digging a notch in wet sand at a beach. Thats what the water going under a deep Vee hull boat does when its on plane. The transducers aren't usually mounted at the deepest part of the hull so they're off to the side of this valley. Sonar doesn't like air and thats what this V notch is doing. Even coming off plane the boat is going to leave a lot of turbulence and air bubbles in this valley, causing a lot of attenuation until the water has time to settle down.
The second one I'd guess is ignition noise. Try an AM radio back by the motor when its running and see if you get a lot of RFI. Thats not going to matter what battery its hooked to. The best thing there is to shield it some how. Simple aluminum foil around the cable "and grounded" would be a good test.
I don't think the third one has any interference which surprised me, if the other sonar was running. The person that recorded this likely had the boat in motion and shut the motor off which caused the boat to slow way down. Half a MPH is going to be just short of not moving at all and thats only going to give you lines from top to bottom cause nothing is changing. In this case hardly any thing is changing. Thats why any object will become elongated top to bottom. Any thing short of a butt smooth bottom will look like lines. He could set the chart speed to 1 to try and improve the view.
The last one is just the same as the one above, .3 mph is worse.

Warren

Unit is on separate battery, not Engine battery. It is prob crosstalk in the cable run, but can't shield the cables. No room in the cable trough. I don't think a RFI filter on the 997 battery would fix the trouble. Also all sorts of cables from engine to console. Tach, ignition, trim, power,etc. Any one (or all) could be causing the interference.

Gonna be tough to fix with so few options.

[Joby @ Humminbird]

If I understand this correctly you have the noise filter to the off position. By turning the noise filter on low you will not be able to tell any diffrence in the image.

[Cane Pole]

If I understand this correctly you have the noise filter to the off position. By turning the noise filter on low you will not be able to tell any diffrence in the image.

The noise will come out with filter settings. I wasn't using the unit. I am just reporting.

Why should noise filters be required if the unit is on a separate battery. That was the purpose of the separate battery.

Using filters degrade detailed reception. Is this not true? You filter noise, you filter out some images, I am guessing, but it is a good guess knowing how filters work.

[Cane Pole]

Unit is on separate battery, not Engine battery. It is prob crosstalk in the cable run, but can't shield the cables. No room in the cable trough. I don't think a RFI filter on the 997 battery would fix the trouble. Also all sorts of cables from engine to console. Tach, ignition, trim, power,etc. Any one (or all) could be causing the interference.

Gonna be tough to fix with so few options.

WarrenMn,

Not sure of the hull. I just glanced at it. Might be why it looses bottom contact. I will check it.

Sure would be nice to have a underwater camera to look at this stuff at speeds other than idle.

[WarrenMN]

Some thing else I've been wondering about is what effect the intake and exhaust on live wells have on the water behind the boat. Looking at the last two images, the left side water column looks just like what mine shows when I run over another boats wake. I was surprised how long the water must hold bubbles from that.
Its not cheap but I use dual side scan transducers and what ever goes on between makes no difference. I attached a friends screen capture that is doing some thing like your post but notice how fast he can go and still get readings on the right side. The left side, if you look close there is just enough signal to show just a ghost of an image. I guess that is actually what the bottom of the river looks like where he was.
As for RFI, it can get in any where, not just power cables. On radios most times it comes in the antenna lead and I look that the transducer and cable as being the same thing. He might want to check his spark plugs and cables for bad connection or some thing. I'm wondering if that is RFI, could be just one plug or a wire with a break. Do they use carbon lead wires on boats?

WarrenMN

[WarrenMN]

Cane Pole. If I ever catch up with you for coffee I'll have to tell you about the day I was playing with a 500 watt amplifier for my transmitter when the apartment manager quick poked his head in and said "What ever your doing stop, one of the other tenants just called up complaining of hearing voices in the walls." Oops

WarrenMN

[Cane Pole]

The 997 is on isolated power, So it is got to be RFI. Lots of things come into play here. Maybe Todd can step in and fill in some of the blanks. I am only the reporter and observer. Todd is my friend. I am trying to help him. He has dial up (lives in the backwoods), so he ain't gonna mess with pictures here.

The situation is tolerable, but it is just aggravating.

[Cane Pole]

Before I forget to say this (I forget some things on occasion), I want to thank all for the help.

Anytime you have to use filters, you are only masking a problem, not fixing the problem.

You sweep dirt under a rug, the dirt stays under the rug. You ever lift that rug, the dirt reappears.

We are trying to fix a known problem, not mask it.