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Noise Suppression

Apr 30th 2012, 15:07

KB4LLA

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Would someone please tell me some of the ways to get rid of or at least cut down on the noise generated by the spark plugs (and other engine electronics) being generated in my 2001 Chevy S10 pickup truck? My FT-897D picks up all of the annoying ticking and whining noises generated during acceleration and deceleration. Thank you.
May 3rd 2012, 20:13

WA0CBW

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Knowing if the noise is getting to the radio from the power feeding the radio or from the antenna can be helpful. Disconnect the antenna and see if you still hear the noise. If the noise goes away then it is being radiated from the source (spark plugs, ignition system, etc. Try using the noise blanker on the radio. Most radios have a pretty good noise blanker and should be able to suppress most of the noise. It may be necessary to use shielded spark plug wires, or noise suppressor spark plugs. Also bond the hood and other body panels so that the noise is shielded in the engine compartment. Any electrical motor may need to be bypassed with a capacitor. A common noise producing motor is the fuel pump usually located in the gas tank. This can be especially difficult to get to.

If the noise doesn't go away when you remove the antenna it is probably coming in on the power leads to the radio. You can check this by powering the radio from a 12-volt battery separate from the cars electrical system. If the noise goes away with the separate battery you need to check the electrical system. Make sure the power comes directly from the battery, not the cigarette lighter plug. Be sure you fuse the positive power lead near the battery. If you connect the negative lead directly to the battery it should also be fused. Another cause of noise can be the alternator. Working in a 2-way radio shop I have found about 75% of the alternator whine is caused by a bad alternator or battery. Corroded connections for the charging circuit or grounds cause about 25% of the remaining noise. In extreme cases bonding of body parts, doors, trunk lid, hood, and other pieces such as the "A" frames, muffler and tail pipe may be necessary.

Hopefully this will give you some places to start looking.

Bill - WA0CBW
ARRL Technical Coordinator - Kansas Section

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