Curing Radio Noise - College of Engineering Bhubaneswar
Contents
1. Smear the area lightly with Vaseline or dielectric grease and reattach This will provide a proper ground at the antenna Be sure the radio chassis is properly grounded to the car body Aftermarket installations are more likely Be sure both ends of the antenna are properly grounded to have a radio that s grounded only by the shield in the antenna a co ax A simple wire added between the component s metal case and the car s sheetmetal will often eliminate any RFI IN LINE NOHSE FILTER There are two ways to reduce noise by using an inductance in a power cable to keep the high frequency noise from traveling or by using a capacitor to shunt it off to ground harmlessly Sometimes both ploys are necessary In fact most of the electrical motors in your vehicle use some sort of capacitor for noise suppression Any good car stereo shop or Radio Shack will have the parts you need The noise filter we show here is one example It has a large inductance in series with the 12 volt power cable to a buzzing aftermarket stereo as well as a couple of small capacitors in parallel The inductance prevents noise from entering the amplifier Supu through the power leads and the capacitors bypass any leftover f This RFI filter goes in line with both power and ground Noise connections Electric motors as we mentioned often have a capacitor in parallel with the armature for the purpose of reducing RFI If the motor s brushes are worn and sparking the2. noise may overpower the capacitor s filtering Most automotive electric motors are not serviceable and they ll have to be replaced if a simple filter doesn t quiet them As we said earlier fuel pumps are difficult to get to in most modern cars they are mounted inside the fuel tank To access the pump or even the wiring that connects to the pump it s necessary to drop the tank out from under the car which is a lengthy messy and potentially dangerous job Replacing Your In Tank Fuel Pump Dec 1997 page 136 On a very few cars you can access the fuel pump from under the rear seat check the service manual Be careful if you attempt to add a filter to the external tank wiring as the filter itself is large and bulky You ll need to securely mount 3 of 5 29 08 2006 2 31 PM Popular Mechanics Saturday Mechanic Curing Radio Noise http hearst corp printthis clickability com pt cpt action cpt amp title Popu it to the top of the tank to keep it from breaking loose over potholes and bumps Soldering One of the most common sources of RFI is poor connections If you find a poor corroded connection or a loose electrical joint don t just crimp the connector tighter onto the wire Remove the connector and clean the wire It may be necessary to trim the wire back a few inches to get past any corrosion inside the insulation There s only one acceptable technique for splicing wires if you re having RFI issues and the common auto
3. your RFI but a nagging misfire Replace any suspect wires with factory or high quality aftermarket wires Check the plugs coil and any distributor for evidence of carbon tracking or arcing as well Intermittents These noises are easy to associate with the source Any RFI that sounds only when one window is going up or down will be easy to blame on the window motor http hearst corp printthis clickability com pt cpt action cpt amp title Popu A cheap AM radio makes a good Geiger counter style device for hunting down RFI Here we re looking for an alternator with a bad diode Mind your fingers Carbon tracking in the ignition system is a noise source 29 08 2006 2 31 PM Popular Mechanics Saturday Mechanic Curing Radio Noise http hearst corp printthis clickability com pt cpt action cpt amp title Popu Which Way Home H Now that you ve pinpointed the noise what can be done about it It depends on whether your RFI source is broadcasting or cabling the MAST noise to your radio This matters because the cure is different Try pulling your radio s antenna lead out If the noise goes away or is substantially quieter it s coming in through the antenna If the noise stays the same or gets louder it s coming in along the 12 volt S power cables E Try removing the antenna from the fender and cleaning the fender sheetmetal and the antenna mount Clean down to the shiny metal using sandpaper to remove any corrosion
4. Popular Mechanics Saturday Mechanic Curing Radio Noise http hearst corp printthis clickability com pt cpt action cpt amp title Popu Popular Mechanics Click to Print SAVE THIS EMAIL THIS Close C PRINT THIS Curing Radio Noise BY MIKE ALLEN Illustrations by Russell J Von Sauers and Ron Carboni Published on November 12 2002 Click here for the Saturday Mechanic archive Degree of Difficulty You re looking forward to the chance to listen to the ballgame having just dropped your purple haired teenage daughter off at her i EASY first semester at college A lot of ballgames actually now that you don t have to listen to her headbanger music with its shrieking vocals and droning guitars But instead of the first inning you hear what sounds like some awful guitar note and it changes pitch as you speed up and slow down turning to a maniacal rhythmic clicking as you wait for a traffic light to change There s no tape in the player What you have here is radio frequency interference RFI Finding The Source There are three classes of RF noise constant intermittent and engine speed following Our hapless father s problem was in the latter category his noise varied up and down in pitch and volume as his engine sped up and slowed down This type of noise is caused by something that varies its speed with the engine Likely culprits include the ignition the alternator or even a fuel injector Constant speed
5. motive style crimp connector isn t it You ll need a good clean high wattage soldering pencil or gun rosin core 60 40 solder and PVC shrink tube Start by using proper stranded automotive grade wire Unstranded household wire will fracture and eventually break Start with wire of at least the same diameter as the wire you re adding to If you re adding a power cable a ground connection or a filter use 12 ga Check grounding points by loosening cleaning and wire for ultralow resistance Strip and pre tin both wires to allow cee you to twist them together for a sound mechanical connection Slip a length of PVC shrink tube over one wire twist together and solder Use enough heat and a sparing amount of solder to make a shiny wet looking solder joint Allow the joint to cool without disturbing it This will prevent the liquid solder from crystallizing as it cools Cover the joint with the PVC tubing and shrink the tubing with a heat gun or carefully with your lighter if you must If the solder joint you re making will be exposed to the elements use shrink tube that has waterproofing adhesive inside it to keep corrosion from creeping into your fresh joint Silicone seal or liquid electrical tape is a good alternative Dress any new wires carefully to prevent chafing on corners Support any components you ve added Remember that even a foot or two of heavy gauge wire can flex itself to the breaking point if it s unsupported Li
6. nd the ignition system Geiger Counter Test Here s our favorite low tech tool for hunting down and killing wild noises a cheap AM radio Tune it to an empty channel around 1400 kHz crank up the volume in your headset and use the radio to sniff out the noise These cheapo radios use a ferrite bar antenna that has good reception along its side but poor reception along its length Once you find the noise within a few feet turn the radio 90 to minimize the noise The top of the radio will point at the source like a gunsight Making Sure Find some way of disconnecting the source of the RFI and check to see if the noise ceases This will be difficult in the case of the fuel pump or ignition but you can pull the belt off the alternator Don t disconnect the alternator electrically the back EMF voltage may smoke the diodes If you think it s a fuel injector try disconnecting it from the harness Plugged Up Virtually all cars today use resistor type plug cables if they use spark plug wires at all If your vehicle is more than a few years old degraded cables may be the source of the problem Remove and replace the cables one at a time clean them of grease and dirt with mild detergent and check the connections to the ends Now get out your ohmmeter and measure the cables resistance along their length they should measure approximately 10 000 ohms per foot Resistance in the megohms or single digits may well be the source of not only
7. nks referenced within this article Click here http www popularmechanics com automotive sub_care_sat index phtml Replacing Your In Tank Fuel Pump http www popularmechanics com automotive sub_care_sat 1272236 html page 1 amp c Find this article at http www popularmechanics com automotive sub_care_sat 1272491 html Click to Print SAVE THIS EMAIL THIS Close 4 of 5 29 08 2006 2 31 PM Popular Mechanics Saturday Mechanic Curing Radio Noise http hearst corp printthis clickability com pt cpt action cpt amp title Popu Uncheck the box to remove the list of links referenced in the article 5 of 5 29 08 2006 2 31 PM
8. noises are usually caused by an electric a Se This stereo power amp is getting an in line noise filter motor most likely the electric fuel pump found in the tank of Most added to its power lead Solder and PVC shrink tube modern vehicles which runs at a constant speed anytime the engine make for a noisefree high current splice is running An electric fan motor will also run at a constant speed until you change the fan setting or turn it off Intermittent noises are easier to associate with a source such as an electric seat adjuster or a power window motor In other words even though the noise comes from a radio speaker it may be caused by any manner of device anywhere on your vehicle ge wee STEREC ee AMPLIFIER CELICE TO FNLARGEF Constants The one motor that s guaranteed to be on whenever the car is lof5 29 08 2006 2 31 PM Popular Mechanics Saturday Mechanic Curing Radio Noise 2 of 5 running is the fuel pump s and unfortunately it s usually buried inside the fuel tank Here s one sure way to tell Turn the key to the Run position without starting the car The pump should run for 2 or 3 seconds Then when the computer senses that the engine isn t running it will shut off the pump to prevent spilling fuel and draining the battery Other almost constants are heater fans wipers and electric radiator cooling fans Engine Speed Noises Candidates here include the alternator voltage regulator a faulty fuel injector a
Download Pdf Manuals
Related Search