sounder periodically looses bottom, screen goes white

[Anonymous]

I have a B60 thru-hull connected to the TZT2. I also have a garmin 545 sounder and its transducer is about 2ft from the B60.

Periodically, while in shallow water (<15ft typically though it did it once in 30ft), the sounder display goes white, the scale on the right side indicates in the thousands of feet (scrolling) and the depth in the lower left corner also indicates a variable depth of 3,000 ft or so.

I turned off the garmin sounder during a couple of episodes with no effect so I'm doubting it is transducer interference.

I always am in less than 150ft of water and spend 1/4 of my time in <15ft. I've reset to factory and tried a number of things with no effect. Any ideas of something I can try?

 

[C-Bass]

Good morning Neman,

What you describe can occur when the transducer experiences turbulence. If you were running the sounder in an "auto range" mode it would not start to cycle to deeper depth scales unless it was experiencing turbulence or air bubbles over the face of the transducer. That is exactly how the "auto range" mode works. If the sounder looses bottom it will cycle to a deeper range automatically. When it cycles to a deeper range the sounder knows to wait longer for the return signal based on a constant which is the speed of sound through water. If it cycles to a deeper range and doesn't find bottom, it will go to an even deeper range to wait longer for the return signal. It will continue to do this "auto range dance" until it picks up a good digital bottom reading. Even in shallow water if there if there are air bubbles interacting with the sounder's transmission through the sounder it will have a hard time picking up what it needs to lock on to a digital bottom number.

There are a couple ways to counteract this from happening. If this happens again I would take the sounder out of "auto range" and put it into "manual range." If you have an idea of the depth, looking at the chart, set the manual range a little deeper than it is by say 30 feet. This will lock the sounder into a range, even if you do not see a digital bottom number you will likely see the bottom contour on the sounder display, and it will stop cycling to deeper depths automatically. Next you will want to verify if the transducer is actually experiencing turbulence. This can be verified by looking at the sounder screen, if you see gaps in the bottom and that gap goes all down the screen then it is likely getting air-bubbles over the transducer. I have included a couple photos of what this looks like below.





If you see this on your screen then you are experiencing turbulence and there is not much we can change in the sounder settings to make it better. The transducer in the photos is a b60 with 12 degree tilt.

There is one more thing you can try to change and that would be the HF and LF bottom Level. The HF and LF Bottom Level is a threshold that tells the sounder basically what strength of bottom return will be used to determine if it is bottom to create a digital depth. The default settings is (0) for both high and low frequencies. The lower the setting (negative numbers) will set the threshold lower and allow the sounder to create a digital bottom return easier, it will be easier to determine the bottom. However is you go to low the sounder could be subject to generate a digital bottom from a return that is not actually bottom, an example of this would be a large school of fish. I would recommend starting at (-20) for both the high and low frequencies. This can be found in the [Menu], [Settings], [Sounder], you will find it pretty much close to the bottom of the sounder menu, so scroll down until it stops.

Good luck, if you still experience problems please take some screen shots of the issue including your sounder settings.

Best Regards,
C-Bass

 

[Anonymous]

Thank you C-Bass.

Noted that I am loosing the bottom in shallow water, sometimes when I am not moving and the water is calm, so no real turbulence. The issue is for sure correlated to being in shallow water. I've not lost the bottom while on plane in water deeper than 15' (one exception to that while at 30'), even while pounding across the tops of waves when I was experiencing the blank areas you described & pictured due to the transducer getting turbulent flow, or even coming out of the water for a sec.

As you recommended, I set the Bottom Level HF/LF to -20.

Regarding the auto/manual range, on the sounder popup menu I set "Autorange" to off. However, there is no parameter(s) related to min/max range under any menu I can find other than under settings-sounder there are "range min" and range max" params under the fish alarm section (I have fish alarms turned off). Under settings-sounder I did turn "Show range slider" on which puts a slider on the sounder display. The boat is on a trailer and the sounder tx turned off so I can't see what the sounder slider does.

Will test in a couple of days and report back w/ screenshots.

Thank you kindly for your support.

 

[Anonymous]

C-Bass, I've posted a couple of screenshots below. Both were taken while at standstill, with the settings you recommended (HF/LF bottom level at -20, manual range). There was an improvement w/ these settings in that I spent more time w/ the depth displayed than before.

The problem of not being able to determine depth is for sure correlated to the depth. The shallower the water, the more likely the depth indication will be lost. I get a bottom reading reliably if I am in more than about 15ft; less than that is hit or miss. Stationary or moving does not seem to matter. The noise at the top of the screen is typical no matter the depth or whether I'm moving or not. I am typically over a sandy bottom.

Any other suggestions are greatly appreciated.

Stationary, in about 3ft of water over sandy bottom. Note the bottom is plotted reasonably accurate but the depth indication is missing. Lots of surface noise:




Stationary, in about 3ft, depth is displayed along w/ a second false bottom and surface noise:

 

[C-Bass]

Good morning Neman,

I am sorry to hear about your trouble. Couple things to try, when running in manual range you can slide your finger up or down the screen to adjust the depth range of the sounder. However it will pretty much stop at 16ft if you do this. Try using the slider bar to get the depth range shallower when in really thin water. You should be able to get the range down to 7.5 ft. That may help. I would also trying running in dual frequency mode in shallow water. What do you have the transmit power set to when in shallower water?

 

[C-Bass]

I would also verify that the "Zero Line Rejection" is turned on in the sounder setup menu.

 

[Anonymous]

Thanks for the reply C-Bass.

Transmit power was the default 10, I set it to 5. Noted I'm never deeper than 120 ft or so (35 mi out!)

Zero line rejection was already turned on.

I will reduce the range and try dual freq as you suggest next time in shallow water.

I assume I should revert these settings when deeper (bottom level HF/LF back to 0, power to 10, range to auto) to get best operation when deeper?

 

[C-Bass]

Good morning Neman,

When in deeper water you will want to turn the power back to turn 10 as you mentioned. You can use the Auto Range as long as you are getting a good Digital Bottom number. If the sounder drops the digital bottom number it will start to cycle to deeper and deeper depth ranges. I would not revert the HF/LF Bottom Level thresholds at this time. As i mentioned before the threshold helps the sounder determine what is bottom and when to create the digital bottom number. This will help in auto range mode, i would leave the threshold at -20 for both frequencies.

all the best
C-Best

 

[Anonymous]

Thanks for the reply C-Bass. Will get out soon and report back. Getting closer each time!

 

[Anonymous]

Been away for a while. Spent the last few weeks on the boat most days trying to resolve the "loosing the bottom depth " issue. Recap: doesn't matter if I'm moving or not, the shallower the more likely it will loose the bottom. If I am in < 15' I do not have a depth reading 50% of the time or so.

One other tidbit, I am running 2 sounders (does not matter if the other on is turned off or not). The furuno always indicates 1-3 feet shallower than the other sounder. Both sounder's 'ducers are within a few inches vertically and I have verified the other sounder's depth is more or less the correct one (in shallow water). Just mentioning this in case it helps. The 'ducer offset parameter does not fix this (ie: I need it to be a negative # to fix the issue and only positive offsets are allowed).

I verified the 'ducer is at 18 degrees from horizontal and I installed a 20 degree B60.

I'm pretty much at the end of the line with this so if there are any other suggestions I'm very happy to try them before moving on.

Thanks,
Chris

 

[Anonymous]

Update: I installed 4.01 after noting that its release notes appear to say that the previous min depth the sounder would work in was 5m and is now 2m. Tested on the water all day yesterday and can report that in under about 15ft of water, I have the depth displayed about 2/3 of the time. A small improvement, but an improvement.

I was offshore for 8 hours yesterday and could find no combination of settings (gain, tx power, bottom level, noise filtering, etc) that would stop the sounder from loosing the bottom every 10-15 min for a period ranging from seconds to a minute. Sitting still w/ motor & all electronics off, bashing over waves, made no diff. The unit basically comes and goes as it likes for no apparent reason.

I am ready to return the head unit to furuno for testing/replacement. Could you please inform of the process? Thanks.

 

[davepjr71]

I don't have the b60 but from conversations on other sites I think your 2nd sounder is creating the problem. The B60 is picking up the return from the other transducer. You shouldn't be running both at the same time or 1 should be on port and other on starboard.

 

[Anonymous]

The issue still exists at standstill w/ all other electronics & the motor turned off. I can see interference on the TZT2 screen if the other sounder is running the same freq & interference rejection on the TZT2 is turned off.

I connected the B60 to my other sounder (Garmin 540) and it was stable over a 3 hr trip in <15ft of water including a lot of time in <6ft. So the issue is with the TZT. Sent it back to Furuno for inspection/repair, they should have it by Mon.

 

[davepjr71]

The issue still exists at standstill w/ all other electronics & the motor turned off. I can see interference on the TZT2 screen if the other sounder is running the same freq & interference rejection on the TZT2 is turned off.

I connected the B60 to my other sounder (Garmin 540) and it was stable over a 3 hr trip in <15ft of water including a lot of time in <6ft. So the issue is with the TZT. Sent it back to Furuno for inspection/repair, they should have it by Mon.

You should have interference rejection turned on and to high and can't run both at the same frequency. When you ran the B60 on the Garmin I'm assuming that was the only transducer transmitting? If that's the case you will not have an issue. You are getting crosstalk between the 2.