Radio Shack 21-1576 Owner's Manual

Contents

Radio Shack 21-1576 Owner's Manual Manual pdf 10 page image

10• The number of nearby CBs operating on the samechannel.• standing wave ratio (SWR) between the antenna andthe CB.REDUCING NOISEBecause your CB is exceptionally quiet, any noise you hearis probably from an external source in your vehicle, such asthe alternator, another radio, or spark plugs. Your CB has anoise blanking (NB) circuit to keep background noise to aminimum. However, strong sources of electrical noise,generated by spark plugs or the ignition of your car, oranother radio, might be more than the circuit cancompensate for. If you suspect engine noise as a source,turn off the engine and operate the CB with the ignition setto ACC. If most or all of the noise stops, the problem is inthe vehicle's ignition or electrical system.These hints may help reduce or eliminate such noise.• Replace old ignition wires with new, high-voltage,noise-suppression wires.• Install noise suppressors on your spark plugs, or installnew spark plugs that have built-in suppressors.• Be sure that the black wire ground connection issecurely attached to your vehicle's battery's negative(GND) terminal or to a good electrical chassis ground.• If problems persist, check your alternator or generator,voltage regulator, and any stand-alone gauges. Noisefrom these sources can be reduced or eliminated usingbypass capacitors at various output voltage points.STANDING WAVE RATIO (SWR)Most antennas are factory adjusted. However, you canusually improve antenna performance by matching itscharacteristics to the CB's RF output power. The built-inSWR meter enables you to do this. The impedance of aCB's output compared to the impedance of the antenna isusually slightly mismatched. By adjusting this impedanceratio to be as close to 1:1 as possible, you maximize theefficiency of your system.21-1576_rsj_012604.fm Page 10 Monday, January 26, 2004 11:39 AM