Citizens’ Band (CB) radio is a radio wave transmission system whereby users can communicate with one another within a limited geographical region. Using a CB radio does not require a licence, and it is a popular way for drivers and hobbyists to communicate with one another whilst on the road. To keep equipment in good working order and to maintain clear communication with other users, a CB radio meter is important. It measures several important aspects of a CB radio’s signal, and indicates whether or not users must make adjustments to improve clarity or protect the device from electrical damage. To select and buy a CB radio meter, buyers should understand CB radio meters in general, the different features available on some meters, and how such features can benefit users. Buyers also need to know how and where to buy a CB radio meter that works with their radio, and how to find one at a price that do not break their budget.
The Basics of CB Radio Meters
The following sections are designed to help readers understand CB radio meters. They address such questions as "What is a CB radio meter?"; "Why is it important?"; and "How do you use one to take readings?" Before buying a CB radio meter, readers should know the answers to each of these question in order to make an informed purchase.
What Is a CB Radio Meter?
A CB radio meter is a device that measures the standing wave ratio in a radio transmission signal. Some models also measure, in watts, the amount of power the radio produces, and the modulation of the radio signal, to determine how much distortion there is in the signal. The meter connects via coaxial cable to the CB radio through a transmission line, and to the aerial that receives the radio’s signal through an antenna line. Based on the readings of the CB radio meter, users can tune the antenna and adjust the ground connection to ensure they get the best possible performance from their CB radio.
Why is a CB Radio Meter Important?
Having a CB radio meter on hand is a good idea, to make sure the radio does not become damaged by a signal overload. A CB radio's standing wave ratio (SWR) is a measurement of the electrical current's amplitude as it travels from the transmitter to the radio antenna. This measurement is expressed as a ratio. For example, a standing wave ratio of 1.2:1 indicates the amplitude is 1.2 times as great at the feed line as at the antenna.
The impedance (i.e. the amount of resistance the electrical current faces during transmission) at the transmitter and the antenna should closely match one another. A high impedance ratio (e.g. 3:1) indicates that the antenna is not receiving a large portion of the electrical energy being transmitted. Instead, the current is being sent back to the transmitter. This type of electrical overload on the transmitter can distort the radio signal and damage the transmitter. Damage may occur immediately, or the transmitter’s transistors may burn out over time. If an SWR reading is high, users can adjust the antenna to correct the electrical current transfer and bring the SWR down to a suitable level.
CB radio meters that measure power output can tell a user if the radio is putting out the right amount of power. This does not prevent damage to the CB radio, but provides information to users that can help correct problems.
Learn How to Take Readings
Before buying a CB radio meter, it is important that users know how to use one to take readings. SWR meter readings are the most important, but those planning to buy a CB radio meter that gives power and modulation readings should know how to take these as well.
To take an SWR reading, make sure the aerial cable is plugged into the meter's antenna input and the transceiver cable is plugged into the transceiver input. Each should be clearly marked on the meter. With the vehicle in an open area (about 20 feet from the closest building), tune the CB radio to channel 20, and turn on the transmit function. There should be a knob or switch on the meter that reads, "calibrate," or "forward". Turn the knob to the calibrate or forward position, and then adjust the meter needle all to the right until it lines up with the "set" or "calibrate" indicator on the scale. Once the needle is in place, turn the calibrate (or forward) switch to the "reflect" position, and the meter indicates the standing wave ratio. A reading of 1.5:1 or below is very good. A reading of 1.5:1 to 2:1 is suitable. Readings of 2:1 to 2.5:1 indicate that an aerial adjustment is necessary. Readings of 2.5:1 to 3.0:1 could be the result of a problem with the aerial position or the ground plane. And 3.0:1 or above (in the red) means that the electrical current is not properly grounded. This indicates the CB radio is in danger of sustaining damage. )
To measure the CB's power output, turn on the meter’s power function. Next, set the range on the meter to the power scale that most closely corresponds to the radio’s power output. If the radio output is around 20 watts, set the meter’s power scale to the wattage setting closest to 20 watts, though never below that number. Speak into the radio’s microphone and observe the needle on the meter's power scale. Test the peak wattage by making a high frequency sound, such as a whistle. The needle on the power meter should closely correspond with the radio’s specifications for power output.
If the meter is capable of measuring modulation, put the corresponding knob or switch into the "set" position. Move the needle to the "set" position on the scale by turning the knob that controls the meter. Turn the knob or switch to the "mod" position, and speak into the microphone. Test several frequencies, from very low to very high. If the modulation meter needle reads 100 per cent, it means the radio is modulating the signal as it should. Thus, the user’s voice should transmit clearly to other CB radio users, as long as their radios are functioning properly, as well.
CB Radio Meter Features
It is important to be aware of the different features offered by some CB radio meters. Meters can take from one to three different types of measurements. Some offer a frequency range within which they can take measurements. Others have a maximum load capacity, or work with a certain line impedance. Thr sections that follow describe these different features and how they may influence buying decisions.
One of the most important considerations when buying a CB radio meter is the types of measurements it can take. As detailed above, CB radios meters may measure SWR, power output, and modulation. Basic models measure only SWR, while more advanced models also measure power output. A few also measure modulation. The highest-end CB radio meters feature two or three windows, one for each type of measurement it takes. Others feature a single window to display all three types of measurements; this may make reading the display more difficult for some users.
Some CB radio meters feature a frequency range within which they can take measurements. These frequencies are the ones across which radio waves travel. Many countries have standards or regulations regarding which frequencies CB radio users can use. The UK has 80 channels around the 27MHz frequency. Many other countries also reserve these frequencies for CB use, though some countries also use other frequencies. Australia, for example, has CB radio stations on the ultra-high frequency of 477MHz, and many European Union countries have channels on 446MHz. Those planning to use their CB radios outside of the UK should check the standards regarding CB radio use in those countries, and should buy a CB radio meter that accommodates those frequencies.
Load capacity is the maximum CB power output a meter can measure. CB radios use a great deal of wattage, and some meters are capable of handling very high loads. It is therefore important to know the CB's power output before buying a meter. Some meters measure outputs up to 100 watts, while others are capable of 5,000 watts.
CB radio meters should also indicate their impedance. As mentioned above, impedance is the amount of resistance a circuit presents to an electrical current. This is measured in ohms, and depends upon the construction of a the feed line. The impedance of power lines that deliver electricity to homes is usually 450 or 600 ohms. The coaxial cables that a CB radio meter uses to take measurements generally have an impedance of either 50 or 75 ohms. A CB radio meter should state whether it requires 50-ohm or 75-ohm coaxial cables. Rather than buy a CB radio meter based on the impedance of the coaxial cables, it makes more sense to buy coaxial cables based on the impedance specifications of the CB radio meter. Sellers sometimes package coaxial cable, or jumper cable, along with the CB radio meter.
How to Buy a CB Radio Meter on eBay
CB radio meters are sold in both local or online electronics shops, and in stores that specialize in radio and communications equipment. Buyers seeking a used CB radio meter may want to check classified ads. However, eBay is a good source for both new and used CB radio meters. You can see the selection available on the site by visiting any eBay page, typing "CB radio meter" into the search bar, and clicking the Search button. The results should include all of the CB radio meters for sale on eBay. You can then browse the selection to find a meter that meets your specifications. You can limit your search to only new or only used items by clicking your preference in the Condition filter box on the sidebar.
eBay also makes it possible to buy from local sellers, which could reduce shipping times and costs. Indicate the distance from your postcode within which sellers should be located and eBay filters out the listings that do not qualify. You might even be able to arrange an in-person pickup if the seller agrees to it.
Anyone who owns a CB radio should also own and know how to operate a CB radio meter. A CB radio meter measures a CB radio’s SWR, and some meters measure power output and modulation, as well. Taking such measurements helps the CB radio user determine if he or she needs to adjust the radio to improve its performance or protect it from damage.
CB radio meters come in a variety of styles. Some take more than one type of measurement. Some offer a frequency range within which they can take measurements. Some can measure greater power output and impedance levels. Using this guide, readers can figure out what kind of meter they want, and match it to their needs and their CB radio Readers should also be able to browse through the hundreds of selections on eBay and find a CB radio meter that meets both their needs and their budget.