Antenna: Testing and Inspection

CHECKING RADIO MASK ANTENNAS

Unplug antenna lead-in at back of radio and plug a test antenna into radio. Make sure test antenna base is grounded to the vehicle chassis. Do not touch the mast. Check radio reception in an area away from tall buildings, metal structures, power lines, fluorescent lighting and power tools. Tune to high and low ends of the dial on both AM and FM, checking weak and strong station reception. Refer to "System Performance Check." If reception is ok, the problem exists with antenna and/or its lead-in cable. If reception is still poor with test antenna, check for aftermarket equipment that may be causing complaint. If ok, service radio.

CHECKING LEAD-IN CABLES

In case of continued reception or noise complaints, always check the lead-in with a digital multimeter (refer to the following illustration and chart). If long jumper leads are not available, check center conductor continuity by jumping the antenna mast to ground and checking for continuity from the center conductor at radio to ground.

When checking resistance, cautiously wiggle the lead-in tip and cable. Consistent readings from table should always be obtained. If not, some portion of the lead-in is intermittent and lead-in should be replaced. Also try:

a. Running a braided ground strap to the antenna lead-in.

b. Changing the antenna lead-in.

c. Disconnecting the lead-in to check resistance.

d. Check in-line connection for corrosion or poor connection.

Description:

CUSTOMER TIPS

HOW TO ENJOY FM STEREO

^ Select Stations Within Range - The best FM fidelity will be obtained from stations within a 16-64 km (10-40 mile) range. Beyond that "noise" or "flutter" may begin to appear due to the "line of sight" range limitations of FM signals.

Solution: Reduce treble response by moving the treble control to the left in fringe areas. On equalizer radios, slowly slide the 10K control down.

^ Realize Tall Structures Can Interfere - Tall buildings or hills may cause "shadows" or cancellation of FM signals (this is similar to the "ghost" or "flutter" effect seen on television sometimes when airplanes are flying in the vicinity). It will sound like a "pop" or momentary "hiss."

Solution: Reduce the treble or 10K setting to a lower setting.

^ Interference From Another Station - Although the circuits in receivers are the most advanced available, there are rare instances where a station being listened to will be interfered with by another station. This only happens when the stations are on almost the same frequency and certain geographical criteria are present.

Solution: Select another station, or switch to tape.