TUBE-GAUGE GUIDE 3N4999 - Caterpillar

65 ( 7YC ),
Challenger 75 ( 4CJ ) TractorsCaterpillar electronic controls meet or exceed the requirements for Radio Frequency Interference (RFI) set by both the Society of Automotive Engineers (SAE) and Caterpillar. In rare cases with certain operating frequencies of 2-way radios some RFI (noise) may be detectable on the 2-way radio receiver. This noise is most often radiated not conducted. Radiated noise is picked up through the antenna system, conducted noise is picked up through the radio power wiring. The noise may be a buzzing or a hiss. It might be possible to squelch out this noise, but even squelched out the noise can reduce the receiving range of the radio in the Challenger application. The transmitting capabilities of the radio are not affected by the noise.
To reduce the noise, it needs to be determined whether the noise is radiated or conducted. Follow the steps listed to find the noise source.
It is possible that the noise is both radiated and conducted.1. With the engine OFF, turn the performance monitor ON and OFF with the key switch.2. Is the noise affected by turning the monitor OFF? NO. This article does not apply since the noise is coming from a source other than the performance monitor.
YES. With the noise present in the radio, disconnect the antenna at the radio.
Did the noise in the receiver stop?
NO. The noise is being conducted from the performance monitor. See the section Reduce/Eliminate Conducted Noise.
YES. The noise is being radiated from the performance monitor. See the section Reduce/Eliminate Radiated Noise.
INSTALL CAB GROUND STRAP: Many interference problems can be reduced with a good cab ground. Use a 7G1060 Ground Strap to connect the right front corner of the cab frame to the tractor frame. The connections must be clean and free of paint.
REDUCE/ELIMINATE RADIATED NOISE:
The following steps should be followed in the order listed. Do as many steps as necessary to reduce the noise to an acceptable level.
1. Change the operating channel of the radio, since the noise from the performance monitor is at specific frequencies.2. Do not use an antenna mounted on the engine hood in front of the performance monitor. Mount the antenna on the left rear corner of the cab roof. For dash area radio positions, route the antenna lead down a rear cab post, along the floor and up to the radio. If the radio is mounted in the headliner, route the antenna lead in the shortest path to the radio. Cut off any excess antenna lead. Do NOT coil the lead up for future use.3. Mount the radio in the left rear corner of the cab. The front right corner of the cab beside the dash is the worst place for the radio to be mounted for noise problems.4. Change the antenna to a 5/8 wave type. This will provide the best noise rejection and improved transmitting/receiving performance. The disadvantage of a 5/8 wave versus a 1/4 wave type antenna is the whip length is longer.REDUCE/ELIMINATE CONDUCTED NOISE:
1. Route the