Topic: Interfernce between 788ci and 997c

[Fishinfinatic]

I am getting interefernce between my 788 and 997.  I didnt used to get this when I first bought the boat (I am 2nd owner
).  Issue started when I updated both units and I dont know if it has something to do with the updates, or something in the settings that were restored to default when I updated them.  Interference is on the unit that is turned on second, and goes away as soon as I shut off the other unit.

[sonar2000]

Check all voltage connections as well as unit connections.
Good electrical connections are important. Especially grounds..

then we can start on the next possibility..

Chuck

[Humminbird_Greg]

I am getting interefernce between my 788 and 997.  I didnt used to get this when I first bought the boat (I am 2nd owner
).  Issue started when I updated both units and I dont know if it has something to do with the updates, or something in the settings that were restored to default when I updated them.  Interference is on the unit that is turned on second, and goes away as soon as I shut off the other unit.

Try turning on and up the Noise Filter menu in the unit that is showing the interference.

[sonar2000]

When you restored factory defaults this means that any setting or options you had previously are changed back to basic unit.

Recheck all of your customised settings and tuning items you may have set just for you..


Chuck

[ITGEEK]

Since the time you had no interference, have you:
  Installed any other electrical devices on your boat?
  Replaced any batteries?
  Re-routed any electrical wires?

You may have caused interference by changing/moving/adding things.

[Fishinfinatic]

Connections seem good.  I did change the battery in the weather sense unit.  I will try the noise filter suggestion as well.  I will be back on the water Saturday morning to try these suggestions and see if adjusting the noise filter will help. 

Will watching the voltage on the unit while it is having the issue indicate any issue? 

I forgot to mention, last time it happened, I pulled the trolling motor out of the water and could hear the "ticking" of the sonar.  I have a minn kota w built in transducer and put my finger on the transducer and could feel the ticking and it was really slow, like once every second.  I am starting to think this is a battery or wiring issue rather than interference between the units.  Thanks for the responses / suggestions.  I will report back after next trip out.

[ITGEEK]

From your photograph, it does look like interference.
If you have one unit on, then turn the other unit on and there is interference, then
turn off one unit and the interference goes away:  I  can't see that voltage would have much to do with it.

Now, here is a question for you:
Is it possible that the trolling motor itself is causing interference?
If so, make sure the second sonar's wires are not close to the trolling motor wires.
And also, that the second sonar is not hooked to the same battery as the trolling motor.

[Fishinfinatic]

The trolling motor has the interfernce kit and the locator at the councel does this as well so I think that rules out the trolling motor?  It is only happening in shallow water.  Once it starts having the issue and I move to deep water, it doesnt get any better until I turn the unit off, then on.  I tried adjusting the noise filter and didnt seem to help.

[ITGEEK]

I don't care what kind of kit you have, you can't rule out the
the trolling motor until you test it.
It is very strange that it happens only in shallow water and
only clears up when you're in deep water and turn the unit off and
back on.

Do this:
Turn on both units and turn on the trolling motor.
Look at both screens.

Then turn off the trolling motor and look at both screens.
If the picture on one or both screens clears up, then it is most definitely
the trolling motor.

[Fishinfinatic]

Okay, trolling motor ruled out as I had both units on and was not running trolling motor as well as pulled the plug for the power to the trolling motor.

[ITGEEK]

Are both units running off the same battery?
If so, maybe think about buying an additional small battery
and only hook one unit to it.

Maybe the software upgrades make the units more
sensitive to interference.

If you do get an additional battery, then try and keep the
wires from both units away from each other.
If they absolutely must touch each other, then route them
at right angles like a cross.

Good Luck.

[Humminbird_Greg]

Fishinfanatic,
So turning the Noise Filter menu up to the “High 3” setting did not help?
Try setting the Lower Range setting of one unit to a setting different than what the other unit automatically selects.

Uh, you are running current software in both units aren’t you?

It is quite common to only see sonar-to-sonar interference at certain water depths.

[sonar2000]

I just have to ask WHY is it common?

dont see this problem in Low or Gar units..

Chuck

[Humminbird_Greg]

Sorry Chuck, I thought you understood more about how sonar works:
It is common to see this happen at certain water depths because the water depth helps dictate how far the sonar beam will spread as well as how much sonar energy gets returned to the other transducer.  What the bottom is constructed of and its shape will also play a part in this as will the overall sensitivity of the unit's receiver and the transmit power used.  If you were in shallow enough water that had a smooth flat bottom that was very soft and your transducers were at opposite ends of a 20 foot boat; than you will probably not see sonar-to-sonar interference.  Go to deeper water or move over a harder bottom or move over a non-smooth bottom and you may see sonar-to-sonar interference.  This is because the sonar beams have expanded enough to overlap at the surface of the water or their is more sonar energy getting reflected back to the other transducer (which the other unit cannot filter out or ignore or due to the additional multiple sonar returns from the increased sonar energy in the water) or the non-smooth surface is reflecting the sonar from the first transducer more directly towards the second transducer.

[sonar2000]

Greg, you missed my point.  I dont see this in other products like we do in HB..
Yes I understand how it works and so do most. which is why the manufactures of some are able to manage this inherant issue..


Chuck

[ITGEEK]

Chuck,
I think that this problem would most likely be the same for any manufacturer of sonars.
Not exclusively to Humminbird.

If you think about it:
If a sonar unit picks up an echo from another sonar unit, it's not really designed to be
listening for two echos.
I guess the same thing could happen if two boats are very close to each other, and
each is using their sonar.

[Humminbird_Greg]

Or the same thing could happen with two radios, radar units or anything else that transmits and receives energy and has their transmitted and received energies intermingle (if they are doing so at the same frequency).

I guess that we could ‘fix’ this by only offering sonar with smaller beam angles and lower sensitivity levels.  Yeah, bet the fishermen would really like that as they would not have to worry about seeing any fish that they are not catching because they wouldn’t be seeing many of them at all.

Now I don’t know about the other manufactures of sonar equipment as I do not work for them and I do not use them.  I would think that they too are limited by the laws of physics (or would this be acoustics?), but I will defer to your greater knowledge in this Chuck.

[Fishinfinatic]

Thanks for the suggestions/input everyone.  Adjusting the lower range on the 997 seems to have fixed the issue.  I was only able to test for a little while tonight, but after adjusting that lower range I never had a problem.  I wont be back out until next week and will report back again to confirm all is still working well.


Thanks!