AM Radio Interference
- Thread starter gratcho
- Start date
Yes, what Bruce asked.
I think others have suggested trying a simple ferrite choke core or "bead" on the power cords, which reportedly sometimes does help:
http://www.radioshack.com/product/index.jsp?productId=2103222
But it might help to isolate power leads and grounds and circuits between the 2 devices as best you can .
I think others have suggested trying a simple ferrite choke core or "bead" on the power cords, which reportedly sometimes does help:
http://www.radioshack.com/product/index.jsp?productId=2103222
But it might help to isolate power leads and grounds and circuits between the 2 devices as best you can .
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What others have said...
I would suggest trying a "choke" ( inductor; toroid ) on the Norcold. It is suspected, and it a likely prospect for "contaminating" your 12v supply. Protecting the radio may also be useful, but stopping the interference near the source is a better plan.
-edit-
Also check for proper grounding, in general, as well as specifically the Norcold. A poor ground on the fridge could disable any shielding already built into the fridge.
I would suggest trying a "choke" ( inductor; toroid ) on the Norcold. It is suspected, and it a likely prospect for "contaminating" your 12v supply. Protecting the radio may also be useful, but stopping the interference near the source is a better plan.
-edit-
Also check for proper grounding, in general, as well as specifically the Norcold. A poor ground on the fridge could disable any shielding already built into the fridge.
Getting rid of RF interference can be rally difficult at times. Chokes or filters on the refrigerator's power leads may help but if it's being broadcast by the circuits in the refrigerator, it will be nearly impossible to get rid of.
Someone asked if this was when running on shore power, battery power, or both and the answer to this question is a very important piece of the troubleshooting process. If it's only on shore power, the 120 volt leads are the place to start. Be very careful working around 120 volt power and be sure any filters you install are designed for 120 volts. You may get the best answer from the manufacturer of the refrigerator. Yours is probably not the first to cause interference on AM radio.
With the refrigerator running and interference on the radio, unplug the radio antenna at the back of the radio. Is the noise still there or did it stop ?(of course the station will no longer be heard). If the noise stopped, the interference is being transmitted through the air just like a miniature radio station. The simplest solution to your problem may be to move the antenna farther from the refrigerator. Use a portable AM radio to see how far from the refrigerator you have to get for the noise to go away. Other things to try would be filters on the refrigerator power leads, making sure any parts of the refrigerator that are supposed to be grounded are actually grounded (with clean solid connections), and constructing a shield for the refrigerator's circuits.
If the noise continues, it's coming through the power wires and filters on these wires would be the thing to try.
At some point, you may have to give up and turn this over to a pro with the equipment and experience to correct your problem.
Someone asked if this was when running on shore power, battery power, or both and the answer to this question is a very important piece of the troubleshooting process. If it's only on shore power, the 120 volt leads are the place to start. Be very careful working around 120 volt power and be sure any filters you install are designed for 120 volts. You may get the best answer from the manufacturer of the refrigerator. Yours is probably not the first to cause interference on AM radio.
With the refrigerator running and interference on the radio, unplug the radio antenna at the back of the radio. Is the noise still there or did it stop ?(of course the station will no longer be heard). If the noise stopped, the interference is being transmitted through the air just like a miniature radio station. The simplest solution to your problem may be to move the antenna farther from the refrigerator. Use a portable AM radio to see how far from the refrigerator you have to get for the noise to go away. Other things to try would be filters on the refrigerator power leads, making sure any parts of the refrigerator that are supposed to be grounded are actually grounded (with clean solid connections), and constructing a shield for the refrigerator's circuits.
If the noise continues, it's coming through the power wires and filters on these wires would be the thing to try.
At some point, you may have to give up and turn this over to a pro with the equipment and experience to correct your problem.
There can be numerous things working against using AM radio in a boat. I'll list a few solar MPPT or PWM chargers, smart battery chargers, inverters, DC/AC dual voltage frigs and even NMEA0183 networks. I have found most marine AM/ FM antennas to be woefully inadequate meaning many people use a wire or a rubber antenna mounted inside the boat. If you get better signal to noise ratio meaning better AM reception the noise can be minimized. I recommend using the Digital antenna company's 4' AM & FM external antenna. Also judicious use of Ferrite or Toroid chokes on power leads to the radio and the offending devices power leads will help. I had very poor AM performance until I installed the 4' fiberglass Digital external antenna. Now all but the weakest AM stations sound fine and I have no bothersome interference.
Bill
Bill
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Even with a truck load of very expensive test equipment, interference can be a challenge to correct. In a recent thread I mentioned that anchoring was somewhere between science and art. Well, dealing w/ interference can often become a bit arcane!
In some instances, the "correct" fix it to cover all bases. Sometimes you can go right to the problem and fix only it. But in summary, the "cure" will involve securing the best possible incoming signal ( ie: antenna stuff ), providing a good clean power supply to the radio ( ie: inductors/chokes/toroid on power leads) ( as well as clean connections!!! ), and blocking the "bad stuff" so it can't leave the "bad actor" ( inductor 'n stuff on the offender power leads ) and improving the shielding ( grounding the offending equipment's cabinet ) as well as ensuring good connections.
About the only good thing related to this process, is that almost all of the corrective measures, even those that do not succeed ( by themselves ) in eliminating the problem, will nevertheless, improve the radio's operation. And most of it is free or cheap.
In some instances, the "correct" fix it to cover all bases. Sometimes you can go right to the problem and fix only it. But in summary, the "cure" will involve securing the best possible incoming signal ( ie: antenna stuff ), providing a good clean power supply to the radio ( ie: inductors/chokes/toroid on power leads) ( as well as clean connections!!! ), and blocking the "bad stuff" so it can't leave the "bad actor" ( inductor 'n stuff on the offender power leads ) and improving the shielding ( grounding the offending equipment's cabinet ) as well as ensuring good connections.
About the only good thing related to this process, is that almost all of the corrective measures, even those that do not succeed ( by themselves ) in eliminating the problem, will nevertheless, improve the radio's operation. And most of it is free or cheap.
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Not to steal this thread, but listening to the ballgame while running the engines is impossible due to static. Is there anything that can be done to help that?
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-> cmariner32
Uh, turn off the radio?
Actually, using an external speaker placed near the helm near helm's man's ears ) can aid in hearing the radio while running the vessel...
Uh, turn off the radio?
Actually, using an external speaker placed near the helm near helm's man's ears ) can aid in hearing the radio while running the vessel...
Is there no noise if running on battery or inverter??
If the noise is really from the reefer it can get out two ways. Via the power cords or via air. many refers are metal and should air shield the noise so check the refer ground connections.
If the noise is really from the reefer it can get out two ways. Via the power cords or via air. many refers are metal and should air shield the noise so check the refer ground connections.
I think I would 1st start with getting as much signal as possible. AM radio is transmitted on very low frequencies and to make matters worse amplitude modulated. Noise rides on an AM receiver much like the modulation (A3). It's difficult to solve many AM radio problems because of poor quality head units and numerous potential noise generators (devices). FM, stored media, USB, Internet based radio are the areas most receiver manufactures concentrate on. It's almost as if AM is an afterthought in today's world.
One way you can track interference is to use a cheap battery powered handheld AM receiver. Use it to walk around and located the actual source from the devices causing noise. Another way is using a cheap telephone tracer probe, they are a basic diode superhetrodyn receiver/ amplifier that picks up amplitude modulated signals (noise) or the telephones match toner. These are available at Home Depot and Lowes and they have a single needle like probe. These can located noise sources down to the actual wire emitting the noise.
Of coarse common sense it to simply turn everything off and turn one device or appliance on at a time to locate the noise.
Since an AC unit was mentioned as a source is the unit properly bonded to the boat? This would apply to all appliances on a boat. Don't rely on the ground wire from the AC power source although they should be checked as well.
Bill
One way you can track interference is to use a cheap battery powered handheld AM receiver. Use it to walk around and located the actual source from the devices causing noise. Another way is using a cheap telephone tracer probe, they are a basic diode superhetrodyn receiver/ amplifier that picks up amplitude modulated signals (noise) or the telephones match toner. These are available at Home Depot and Lowes and they have a single needle like probe. These can located noise sources down to the actual wire emitting the noise.
Of coarse common sense it to simply turn everything off and turn one device or appliance on at a time to locate the noise.
Since an AC unit was mentioned as a source is the unit properly bonded to the boat? This would apply to all appliances on a boat. Don't rely on the ground wire from the AC power source although they should be checked as well.
Bill
Yes. Looks to me that I have two issues; the antenae needs upgrading - it's currently feeding into the radar arch and is either tied into the VHF (not likely) or onTo the arch itself? Also my Norcold frige AC sorce has a ton of noise in the line. I'm going to look for lose ground and maybe try some type of isolator.
thanks for the advice!
thanks for the advice!
That doesn't make a lot of sense to me. Do you have an AM (usually AM/FM) antenna? What does it look like?
Tracking and correcting interference such as you are having is very difficult and hit or miss for someone who doesn't understand electrical and electronic circuits. For example "putting a choke" on the power leads could mean different things to a pro and to an amateur so just because you installed one and it didn't help doesn't mean that's not the solution or part of the solution.
Did you try the troubleshooting suggestions I posted? What were the results?