# Fish Finder causing interference with VHF Radio



## Catch-N-Eat (Apr 1, 2003)

I am noticing that my "Bottom Line" fish finder is causing a significant amount of interference in my VHF radio. Each time the finder "Pulses" it is picked up in the radio.

I am sure that Radio Shack or some other place would by happy to sell me a "High-Dollar" cure, but I thought I might check with you guys first.

Thanks!


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## Shad (Jan 28, 2003)

Check if you have a good ground. That was my problem. Good luck!


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## Muddpuppy (Feb 18, 2003)

Good advise Shad........more of us should take time out to stop and smell the roses.  Oh and about the ground, I bet'cha that's the fix too.....Good luck brothers


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## ficious (Aug 28, 2002)

If the ground doesn't do the trick, try running the power lines and antenna for the radio up the opposite side of the boat as the transducer cable. Hope that either does the trick.

ficious


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## Catch-N-Eat (Apr 1, 2003)

Thanks for the advice Shad and Mudpuppy. Now comes the fun part, trying to sort out the wiring and FIND the ground! 

The power lines and antenna are on opposite sides of the boat. (Thanks Ficious)


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## sfw1960 (Apr 7, 2002)

When you READ your instruction manual is says NOT to mount them close together.......
Good luck , but I bet they are less than 2 feet apart....
Might have to move them apart

 SFW


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## Catch-N-Eat (Apr 1, 2003)

Thank you SFW, for your reply. The units are over 4 feet apart. The finder is mounted on the top left part of the dash board and the VHF is mounted to the right of and just below the steering wheel. 

These units were all installed by the previous owner. I have most of the manuals and have gone through them. I can also assure you that I am of reasonable intellect and functionally literate.


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## sfw1960 (Apr 7, 2002)

That SUX....
it's quite possible that the wiring isn't run seperate , I can recommend a large value capacitor (4700 uF/25VDC or higher) right near the radio's DC input - to attempt to filter any line noise - but it sounds like an induction signal from the sonar's transmitter , bleeding into the antenna to the VHF - I used to trouble shoot these things for a living , and they can be a b*[email protected] to isolate , hunt down & kill....
try bringing a seperate battery along & wiring each unit alone to see if taking one or the other "off" the boat's main power stops or reduces the situation , honestly I would guess that the transducer cable & VHF coax are strung along the same path in an unseen portion of the gunnel , or bilge area.
I hope this gives you a basis to start , and help you isolate & remove the offending crosstalk....
Again , I wish you luck ~~
 Robert


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## POLARBEAR (May 13, 2002)

ah! well i cant speak in code like robert, i thought i would mention that when i went to replace my spark plugs they offered me 2 different kinds. the more expensive ones had a better resistor to filter out noise? not sure but i ddint see it mentioned and it may be a cheap fix. good luck btw a (Q) on the plug described the better resistor.


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## ESOX (Nov 20, 2000)

You didnt mention it so I will ask, are you running an electric trolling motor? The Vhf should not e wired to the troller battery, in fact nothing should be wired to the trolling motor battery(s) except for the trolling motor. The Maximizer circutry on Minns, and the comparable circutry on Motorgiudes can cause interference with just about anything. Also, as previously mentioned, run separate circuts for each electroinc device, do not share hots or grounds.


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## Jason Adam (Jun 27, 2001)

Most problems I've seen with interference on a VHF or FM Radio is because the Sounder and the Radio share a common ground or power feed. Do as sfw1960 said and take a separate battery and wire your radio dirctly to that alone, then see if it goes away. If it does, you need to run separate power and ground to the battery, not to a fuse or distribution block.

If it is still there, I would leave it hooked that way, and try to pull your antenna wire out and route the antenna wire away from any other wires that it may be running with or wrapped around in your gunnels, or if you have a spare antenna, just hook that up, and see if the problem goes away. If you radio and antenna are good stand alone, then a capacitor might have to be added if you have a "noisy" charging system, or you'll have to clean up and re-run some wires.


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## Catch-N-Eat (Apr 1, 2003)

Thanks again guys. 

I have made some progress with the grounding. The feed-back from the sonar to my VHF is now reduced to something I can live with. 

SWF- I think you are correct about the signal from the sonar bleeding into the VHF. I must have had two problems and I am now down to that... I HOPE!

I am probably going to get a filter for the power supply to the VHF and see if that helps, I know it will not help if there is actually bleed-over from the sonar to the VHF antenna.

I don't have any engine noise in the radio and my electric trolling motor does not seem to be an issue either.

NOTE TO THE MODERATORS: Sorry about posting this on the wrong site. I am still learning my way around.


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## Catch-N-Eat (Apr 1, 2003)

Thanks Jason-

I am going to try running a direct line to a battery before I go any further.


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## sfw1960 (Apr 7, 2002)

KooL!
I'm glad to hear that you have made some progress with it , and *even* if you can't get rid of all of it , you have reduced it to somewhat of a more bearable level....
If you get an "inline filter kit" , make sure it is one capable of handling 10 Amps - the "El CheepO" variety will burn up , or starve your radio of needed power to produce the 25 Watts transmitter output it is probably capable of. 
If ya post someting in the wrong area , usually the Mods will let ya know about it , and move it for you.
We try to help..... 
keep us informed!
 Robert


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## SalmonSlayer (Jan 18, 2000)

If you're still getting bleed over from one power cable to another, try insulating one or both of them seperately by running each through an old section of garden hose. I had this problem with my old radio, but not with my new one...the old cable was too thin I believe and got a lot of current leakage. Hope this helps!


ben


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