Terrible radio interference, out of ideas.

[John_S]

Re: Terrible radio interference, out of ideas.

the noise is on AM and FM stations, everything else is very clear

the powered antenna is grounded to the same ground as the radio and is powered by the radio.

the other antenna had the static issue aswell.

no external amp.

I think that answered my next question, "Is the chassis tied to ground?".

It sounds like the noise is coming in from the antenna vs power or chassis. Do you have an antenna with a rather long coax? Maybe from an old car. You could see if the noise is diminished by distance or orientation, to validate that is where it is coming in.

 

[John_S]

Re: Terrible radio interference, out of ideas.

Sounds like your have a "ground loop". As suggested earlier, connect the battery grounds together and see if it resolves the problem.

I am wondering if a prior discussion on inatvertant grounding is pertinent? If a tin boat, and grounded the hull by the motor (Silvertip discussion), and the chassis is attached to or grounded to the boat. In that case the grounds from the different batteries are tied through the hull.

 

[turbinedoctor]

Re: Terrible radio interference, out of ideas.

Have you tried to reroute your power wires for the radio yet, you may also want to make sure your antenna wire is away from the other power wires too.

 

[RickJ6956]

Re: Terrible radio interference, out of ideas.

Since the problem only happens when using AM and FM ... you've swapped the radio ... and you've swapped the antenna ...

The last radio system check I would do is to follow Imported John's thought and make sure the antenna coax is not damaged, that it runs at least 1 foot away from all other wires, and the plug is secure in the socket.

After that, turn your attention to the other devices that are causing the problem.

 

[wire2]

Re: Terrible radio interference, out of ideas.

I'd be inclined to try to discern between the noise being introduced by the radio power leads or the antenna.
Stop by an electronic surplus store, look for a ferrite core inductor to put in series with the pos lead close to the radio. Then add a pair of electrolytic capacitors (1,000 ?F, 40 vdc or similar) between pos and neg, one before, and one after the inductor.
That will kill any noise that might come in on the power leads.

If the noise is still there, use an ohmmeter to verify a good connection between antenna ground and radio chassis ground. Another capacitor at the antenna motor + and - will be an easy experiment.

 

[turbinedoctor]

Re: Terrible radio interference, out of ideas.

Hey Pontoon, got any updates yet?

 

[Pontoonfoon]

Re: Terrible radio interference, out of ideas.

Well not really.

I talked to the local merc dealer and his suggestiong was t buy an in-line RF filter for the antenna, his theory is low level noise from the devices (fish finder, aerator) are being picked up by the antenna.

but so far no I have made absolutly no progress.

 

[bruceb58]

Re: Terrible radio interference, out of ideas.

I talked to the local merc dealer and his suggestiong was t buy an in-line RF filter for the antenna, his theory is low level noise from the devices (fish finder, aerator) are being picked up by the antenna.

There is a real easy way to test the theory that it is coming in through the antenna. Remove the antenna and ground the antenna input to see if you still have your interference.

 

[Kevinmcm]

Re: Terrible radio interference, out of ideas.

Your dealer is right, but did he explain WHY? The fish finder has a transducer on it, meaning, it projects RADIO waves. Although on different frequencies as the FM band, it is the closest thing to the radio, much closer than radio station, so your radio is "seeing" these radio waves, but has no idea how to interperut them, so, all it knows is static. You may even notice a difference when you scan through the chanels as u get closer to the transducers frequency, but it may be so small you might not. Your areator is a brush driven motor, and little tiny sparks, as small as they may be, create radio waves too. Its kinda like the old TVs when your mother was vacumming when saturday morning cartoons were on, the picture went to snow. Same thing. As for the fix, a filter in your antenna line will be the only fix. It has nothing to do with the route of your power wires, not on what your explaination of symptoms are. Hope this helps a little more.

Kevin

By no means was I trying to be condesending to anyone here or be hateful or "better" than anyone. Just thought an explanation may make more sense of what was happening and why these items only were the ones creating the problem. If I offended anyone, I am sorry.

 

[NYBo]

Re: Terrible radio interference, out of ideas.

Since A fishfinder's transducer's main output is sound waves, would a grounded layer of foil around the transducer be adequate to block out any incidental radio waves.

 

[Kevinmcm]

Re: Terrible radio interference, out of ideas.

Hmmm, I dont know, but certainly one for the bench test sometime! I am not sure how one would keep foil on the transducer underwater,a dn think of the questionsa t the ramp!

 

[TerryMSU]

Re: Terrible radio interference, out of ideas.

Since A fishfinder's transducer's main output is sound waves, would a grounded layer of foil around the transducer be adequate to block out any incidental radio waves.

Depends on how the finder is projecting the radio waves. Could be the finder head unit, in which case, it probably will solve the problem. Unfotunately, you will not be able to see the display if you shield the head unit that way. It could be either the transducer cable or the power cvable to the unit. Harder to shield those. If it is the actual transducer, it should already be somewhat shielded by the water around it. Even freshwater is somewhat electrically conductive.

KevinMCM...
Great explanation. Technically acurate, but still understandable to the non-engineer.

 

[turbinedoctor]

Re: Terrible radio interference, out of ideas.

Kevin wouldn't the pulsating power going to the transducer through the cable also create a type of induced frequency into the power wires of the radio if they were run close together, much like the non resistor plugs in the older cars. My line of thought was to reroute them to see if it helped to eliminate the noise and if so the maybe use a twisted shieled cable for the radio power wires to drain the induced noise before it got to the power wires.

And no you did not offend me in any way. I enjoy reading others ideas and learning something new.

 

[Kevinmcm]

Re: Terrible radio interference, out of ideas.

I suppose your interfence would somewhat come from the power wires, but you have what is called an isolated sysytem, meaning your power doesnt share anything relevant to the transducer/ fishfinder. Meaning, you dont share the same ground plane, (like the old cars that were using one battery and the whole car was a ground plane), so it is very unlikely you have power interference. Possible yes, but highly unlikely. As for shielded cable, the finder cables are shielded, and hooked to the sending unit, and left unhooked at the transducer, thats the way it should be. IMHO the only way to solve this is to put an in-line filter, near the radio, on the antenna line, and dont ground the antenna to the boat.



In my 40 hr week job, I am an electrician, and I also install Lethal fences in federal prisons, and microwave security systems with CCTV. My experiance with interference has had me scratchin head a time or two, and I try to explain to the best of my abilities, how this stuff works so my fellow friends will understand better. I am not saying my knowledge is better, or i know more, I just hope someone else can benefit from the bald spots I rub on my head a time or two!

I just spent four days troubleshooting a microwave system in Pennsylvania, and after many conference calls and finding a solution in the field, the manufacture had to admit their own book was wrong! YES! one notch for the little guy!

 

[Audio Greg]

Re: Terrible radio interference, out of ideas.

Its a Sony AM/FM/HD/XM

before the sony it had some POS "Dual" radio in it.


Ive tried a few different antennas, the one I stayed with is a 12V amplified antenna.

I hate "amplified" antennas. Did you ever try AM/FM on this Sony with a standard antenna (simple wire lead)? If not, PM me your address. I will throw one in the mail for you if you promise to post if reception compares to the amplified one you have now.

Looks like all the replies are great ideas. I just wonder if simplifying your signal capture method might be the "magic bullet." Either way, please post if you solve this mystery... or summon that lake troll.

Greg