RADIO TROUBLES
Compliments of Firestik® Antenna Company Technical Support Team
Copyright © 1996 Firestik® Antenna Company
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INTRODUCTION CB radios are designed to be two-way devices. That is, they receive and they transmit. These are the two primary functions. Both functions share some common circuitry, but they also work independently of one another. We often hear from people that say, "I receive okay but nobody can hear what I am saying" or "They hear me but I don’t hear them." Because we are an antenna manufacturer either of the two statements are often followed by "Do you think there is something wrong with my antenna setup?" The radio manufacturers most certainly field technical calls that question the radios performance when indeed the problem is antenna related. Likewise, we field numerous calls from individuals that want to fix an "antenna problem" that really is not an antenna problem. In this article we will offer our angle on some of the more common problems we run into regarding radio troubles and offer some ways for you to troubleshoot and/or fix the problems. WIRING POWER TO THE RADIO This is one of the biggest problem areas we run into when performance problems occur. Do not overlook the 12 volt power line that feeds the radio. Just because the lights come on, do not assume that sufficient power is available. It is our strongest belief that the power to the radio should come directly from the battery. There are several reasons why. First of all, it is what we call "clean power." When you tap into a circuit under the dash there is no telling, short of studying schematics, what other accessories are sharing that circuit. If there happens to be a relay or motor in or near the tapped into circuit, there is a possibility that the radio will pick up "noise" and or realize power drops that could affect performance. Some of the "hardcore" radio operators will use a piece of coax to run power from their battery to the radio. By using the center conductor as the positive lead and the shield as the negative lead, a clean and shielded power source is available. Another advantage of running straight to the battery is that the radio can be used at anytime. You will not need to turn on the ignition switch as would be required on some circuits. In the event of an electrical problem, communication will still be possible. As a final note on power, make sure you have full battery power available at the radio. It is a very good habit to check the voltage to see that you have 12 to 14 volts available. The fact that the radio lights come on does not mean that you do! We have seen this problem numerous times. The lights will light up with as little as 5 volts but your transmitter and receiver will not function properly without full power. Corroded connections, poorly crimped connectors and wire gauges that are too light to carry the needed current are power thieves. Two strands of wire in a 20 strand bundle will give you the false impression that everything is okay but the radio cannot draw enough energy to function as intended. And yes, it will affect receive just as much as it will affect transmit. We recently looked at a problem installation on a motorhome that "would not receive over 75 yards." The owner tested three different radios and none of them performed better than the other. He assumed the antenna system was at fault even though the SWR was below 1.5:1 on all channels. When we checked the power feed we found less than 7 volts available. As soon as we ran a good line we were talking to people several miles away. BLOWN TRANSMITTERS Any condition that causes high SWR has the potential to wipe out the transmitters power transistor. If you are receiving signals but nobody responds back, you may have lost half of your radio. It happens all the time! If you apply the principles of "plug-n-play" or "point-n-click" to a CB installation there is a strong probability that money will leak out of your account. Shorts in the antenna system and/or high SWR will damage your radio. Shorts are the worse! Untuned and untested systems are next. We always recommend that a volt/ohm meter be used on the antenna system BEFORE the coax is ever connected to the radio. Ground-plane dependent and no-ground-plane systems have a different testing procedure and you need to be familiar with the specific characteristics of the type of antenna system you are installing (There are articles on this subject in our library). However, in every case, if you have any continuity between the antenna base and the antenna mount on applications where a feed-through antenna stud mount is being used, you have a problem, and the radio should not be used. And, with the coax disconnected from the radio, if you have any continuity from the antenna base to any ground point on the vehicle, that too indicates a problem. High SWR caused by untuned antennas will not toast the transmitter during testing. The problem is a time-based one involving heat build up. During SWR testing the transmitter is activated in short bursts. Cooling off time exists between calibration and the collection of the readings. Until all components are tested and the SWR adjusted, you should not keep the microphone "keyed up" for longer than 10 seconds at a time while calibrating and testing, especially if at any point the SWR readings are at or above 3.0:1. Read all that you can read and go into your installation with knowledge. With so many possibilities it is nearly impossible to answer every question that will crop up, But if you get a grip on the fundamentals, you will be well on your way to getting the maximum performance from your 2-way radio. |
Updated: 2023.12.05