When trying to cure an interference problem, its important to track down the cause of it, so you can take steps to stop it...
- Does the noise only happen when you are doing a particular job with the machine, or using a power-take-off, or do any fans, pumps or motors seem to trigger it?
- Switch off your air-con... does the interference go away?
- Does the pitch of a whine or speed of any ticking sound vary with engine speed or work effort?
- Does it happen in a certain location?
- Does it happen at regular times in the day?
- Do you get a "pulse" of signal or loud crack through the speaker when you switch systems on or off? (If so, this could mean bad earth bonding and you should approach your service agent or manufacturer.)
Also remember that Interference can be given out by all manner of electrical systems commonly found on farms - flourescent tubes, refrigeration and pumping systems, irrigation systems, overhead and underground power lines, even metal grain silos have been known to cause interference.
A process of elimination...
To trace the source of interference in a particular machine, start with the engine and ignition off, along with all other mechanical and electrical systems.
Turn on the ignition without starting the engine and listen for any interference - sometimes fuel pumps, preheaters and other motors and circuits activated by the first position on the ignition can be a cause of noise.
Start the engine, and operate any mechanical and hydraulic systems one after another, listening for the one thats causing interference - hopefully you can track down where it's coming from, and can go from here.
Sometimes cooling fans and similar can be the cause of interference, so check these when the are on too.
Things you can do to help
Make sure that your power and aerial cables dont run close to the interference source - re-route your aerial lead if necessary.
If you have already made sure that your power feed is direct from the battery, try finding how the interference causing item is powered - it may share a battery terminal with your feed.
Check that the earth bonding is all still in place - check with the machine or vehicles manufacturer regards this.
You might need to supress certain circuits individually - usually done with a capacitor or choke placed on the power connections for the item in question (fuel pump, etc). Again, your machines manufacturer should be able to help here, but get in touch with us if not.