DFF3D Noise Problem

[MarMax]

I had kind of hijacked another thread to discuss TVG and settings and ended up focused on a noise problem. Here is the hijacked thread http://furunousaforum.com/viewtopic...0fadac5a&sid=6e086c0e2ed66492637a6100fadac5a9

Figured I'd better get a thread going with a proper title to continue things. I ended up doing a lot of testing with the ohm meter and making some changes to the wiring. There were two cross connections between the ships (earth) ground [GREEN] and the 12V system ground [BLACK]. The first was from the factory connecting the grounding plate to the -12V of the main battery. The second was my error quite a while back when I connected the shield to the 12V ground of my NMEA 2000 power.

Disconnecting the grounding plate from the battery ground was easy. Figuring out where my ground loop between the remaining ships (earth) ground and 12V ground was about 4 hours of testing plus removal and re-installation of the DFF3D and the autopilot. In the end I achieved a open circuit between ships (earth) ground and the 12V system ground.

Took the boat out yesterday to see how things looked with the DFF3D and here is three images for review.

Snips had noted that the speckle in the center beam of the multi-sounder was electrical noise (from the other thread). It's amazing what another point of view does when you are trying to optimize your fish finder settings. His point that there was pattern (electrical interference) to the speckle is true, yet I had not noticed this, even though the speckle was bothering me. Here is the prior screen shot for those that don't want to wade through the other thread.

Hopefully the latest screen shots show some improvement in the electrical noise problem. I'll always have more turbulence than a thru-hull transducer, especially since my transom mounting location is not ideal. I'll look forward to any feedback you have Snips. Thanks again.

 

[Snips]

MarMax,
Good for you for taking the time to go though your system.

While most of the time grounding will help clean up noise it can (in some cases) add a path for noise to enter a system. I have seen this on the vessel we use for testing. Here we have both a DFF3D and WASSP systems. The WASSP DRX's need to have a case ground to eliminate center channel noise but if I add that same ground to the DFF3D module it will induce the center channel noise. I can't answer why, but it does. Your last screen shot is showing the center channel noise in the cross section, triple beam and history views.

Snips

 

[MarMax]

OK, the 297 foot screen shot is showing noise, got it. Now the question is why? All the screen shots were taken on the same day, a few hours apart, and without changing anything electronically. All the electronics were turned on at the start of the day and turned off at the end. What would cause noise in that picture at that time?

The only other thing I can think of trying is to connect the DFF3D earth ground to the grounding plate. I was going to try this but thought I'd solved the noise problem based on how things looked.

 

[Snips]

MarMax,
Noise always has a source, most of the time it easy to trace down and other times it can be like finding a needle in a hay stack. I start with a dead ship (at the dock) with only one thing turned on. I will set the gain very high so I can see if any noise is present. If I see noise, I will either add or remove the ground. In doing this you "should" see a increase or decrease in the noise. If you see no noise at the the dock and it starts to appear later in the day, then you need to start this process when the noise starts to appear. When I look at the last screen shot (297ft) I see weak bottom returns in both the cross section and triple beam compared to what I am used to seeing at that depth (see below). Maybe this is due to the water flow over the transducer but it's hard for me to tell from that screen shot.

Snips

 

[MarMax]

Thank you Snips. Next time out I'll go solo and spend plenty of time at the dock first. I'll try the one thing at a time approach and see what happens.

 

[kgb666]

MarMax,
Noise always has a source, most of the time it easy to trace down and other times it can be like finding a needle in a hay stack. I start with a dead ship (at the dock) with only one thing turned on. I will set the gain very high so I can see if any noise is present. If I see noise, I will either add or remove the ground. In doing this you "should" see a increase or decrease in the noise. If you see no noise at the the dock and it starts to appear later in the day, then you need to start this process when the noise starts to appear. When I look at the last screen shot (297ft) I see weak bottom returns in both the cross section and triple beam compared to what I am used to seeing at that depth (see below). Maybe this is due to the water flow over the transducer but it's hard for me to tell from that screen shot.

Snips

what settings did you use for this picture? Gain? TVG? others please? because i am not seeing such readings and i do not have neither interference nor Noise.

 

[MarMax]

what settings did you use for this picture? Gain? TVG? others please? because i am not seeing such readings and i do not have neither interference nor Noise.

kgb666, you'll need to clarify if you are referring to Snips picture or the ones I posted. For mine, except for the 297 foot picture, where I was playing with the transmission power, the settings are probably as follows.

-Tx power set to auto and Tx pulse set to Short2

- Gain in the 50-65 range since I was playing with it all day

- Clutter set to 0

- TVG was set at 5 and TVG depth was varied all day but I was setting it about 20% deeper than the depth (120 for 100; 240 for 200, etc.)

 

[MarMax]

what settings did you use for this picture? Gain? TVG? others please? because i am not seeing such readings and i do not have neither interference nor Noise.

kgb666, you'll need to clarify if you are referring to Snips picture or the ones I posted. For mine, except for the 297 foot picture, where I was playing with the transmission power, the settings are probably as follows.

-Tx power set to auto and Tx pulse set to Short2

- Gain in the 50-65 range since I was playing with it all day

- Clutter set to 0

- TVG was set at 5 and TVG depth was varied all day but I was setting it about 20% deeper than the depth (120 for 100; 240 for 200, etc.)

 

[kgb666]

thank you and well noted...