Fish finder interference

[zippy83]

Hi all,

I have a problem with my two fish finders. I have two lowrance sonars one is hds12 and the other is hds9. I have networked them together and both have separate power sources. Hds9 is hooked up to the trolling battery and hds12 to the main outboard starter batterie. When I turn on my trolling motor I get really bad interference on both of my units. The trolling motor is at least 17 feet away from the main transducer.

I called lowrance but they are not sure what to do at this point. When using the trolling motor it is almost impossible to read the sonar or the structure scan.

Anyone have any suggestions on this one?
Thanks
Zipp

 

[GA_Boater]

I would try powering the 9 with the starting battery to test. Often noise is on the power feeds and the TM my be introducing the noise.

Are both batteries 100% isolated from each other? No common ground (-) connections or power (+) connections, including chargers/maintainers?

 

[gm280]

I agree with GA above. Try connecting both locators to the starter battery just to see if the noise is still there. If it is, the noise in not coming from the battery supply lines but via the transducer(s). And sadly that will be very hard to filter out. If the nose is not there, then you have a few options to filter out the noise. You can install filters in the battery lines of the trolling motor battery to the locator. They make and sell them for that very issue.

Is your trolling motor a standard setup or does it have a Digitizer/PWM setup? If it uses a Digitizer to drive the motor, more then likely the noise is being produced via that pulsing circuit. JMHO!

 

[NYBo]

Another vote for connecting both to the starting battery. The units aren't truly isolated from each other even though they are connected to different batteries. They are connected via the network.

 

[sam am I]

Or temporarily just disconnect the network interconnect, fire them both up and run the trolling motor.........that'll get ya pointed in the right direction as to what to do next as well. e.g., if they both still have issues after the network disconnect,, it's neither a single power source or a network ground loop for example but, perhaps simply the trolling motor interfering possibly just by RF/EMI via radiation and not conduction. If conduction and the interference path is just one power source, then one unit should clear up. Probably 9 ways to the Sun to go about it, just have to eliminate each possibility at a time by trial and error

 

[dingbat]

The trolling motor is at least 17 feet away from the main transducer.

Describe your setup?

The "main transducer" suggests your using more than one transducer in this setup

 

[zippy83]

I would try powering the 9 with the starting battery to test. Often noise is on the power feeds and the TM my be introducing the noise.

Are both batteries 100% isolated from each other? No common ground (-) connections or power (+) connections, including chargers/maintainers?

Hi. Yes both batteries are isolated one is in the front and the other in the back. I guess I could try and power the hds9 unit with the starting batterie and see what happens.

Thanks

 

[zippy83]

I agree with GA above. Try connecting both locators to the starter battery just to see if the noise is still there. If it is, the noise in not coming from the battery supply lines but via the transducer(s). And sadly that will be very hard to filter out. If the nose is not there, then you have a few options to filter out the noise. You can install filters in the battery lines of the trolling motor battery to the locator. They make and sell them for that very issue.

Is your trolling motor a standard setup or does it have a Digitizer/PWM setup? If it uses a Digitizer to drive the motor, more then likely the noise is being produced via that pulsing circuit. JMHO!

I have a standard Minkota power drive 55lb.
Out of curiosity what are those filters called and where can I buy one?

Thanks
Zipp

 

[zippy83]

Describe your setup?

The "main transducer" suggests your using more than one transducer in this setup

Simple setup. Minkota 55lb power drive in the front hooked up to a battery in the front along with my hds9 unit. Hds9 uses network cable to hook up to the hds12 on the console. Hds12 connects to the starter batterie. I have two transducers one is a regular sonar and the other is a hd2 structure scan transducer.

Thanks
Zipp

 

[gm280]

I have a standard Minkota power drive 55lb.
Out of curiosity what are those filters called and where can I buy one?

Thanks
Zipp

zippy, there are power line filters on the market for filtering out noise. One company manufacturers them and they are called Newmar PC-10 and PC-25. Do a quick search and look at them and see which would be the best for your power lines IF you determine that is the source of the noise.

 

[Barnacle_Bill]

Never use the trolling motor battery for powering electronics. Electronics do not like power surges and you do get them every time you step on the go button. Plus your troller has a maximizer built in that can cause interference.

 

[GA_Boater]

It could be the network. Network cables have a braided or foil ground shielding wrap. With two different batteries, the grounds are being tied together through the cable shielding, Powering the front Lowrance from the starting battery should eliminate the interference from the TM since the TM power would be isolated from both FF's.

I hope!

 

[dingbat]

Simple setup. Minkota 55lb power drive in the front hooked up to a battery in the front along with my hds9 unit. Hds9 uses network cable to hook up to the hds12 on the console. Hds12 connects to the starter batterie. I have two transducers one is a regular sonar and the other is a hd2 structure scan transducer.

Thanks
Zipp

if your regular transducer is anywhere near the foot of the trolling motor, that your problem

 

[fishrdan]

I'm with the other guys, power both sonar's off the same battery, starting battery. Pulling power off the trolling battery for the HDS9 and then "networking" it to the other sonar could cause back-feeding voltage through the network cable, or possibly a ground loop.

Your start battery will most likely always have a higher voltage as it's getting charged by the outboard and has minimal power draw, where the trolling battery is constantly being discharged and only charged at the end of the trip. (Yeah you could have a charger for the TM battery that runs off the outboard, but I'm assuming that's not the case) If the start battery is at 12.7V and your TM battery is at 12.5V, and then you run a network cable between devices on each battery, that .2V difference could try to equalize across your network cable......

 

[dingbat]

if your regular transducer is anywhere near the foot of the trolling motor, that your problem

Also, how are you connecting the two units? NMEA 2000 or ethernet?