CB Radio Amplifiers Buyers Guide

Like if this guide is helpful
CB Radio Amplifiers Buyer's Guide

A CB radio amplifier is used to increase the power a CB radio’s signal. It is similar to an audio power amplifier, where low-power audio signals are increased to higher levels.

The audio amplifier originated in 1909 from the triode vacuum tube developed by Lee De Forest. This device contained three terminals with a control grid modulating a flow of electrons from a plate to a filament. The first AM radios used this type of technology. Vacuum tubes were the basis for early power amplifiers, some of which achieved notable high quality. Modern audio amplifiers are based on solid-state devices, such as field-effect and bipolar junction transistors, but there are still some amplifiers produced utilising the valve sound.

The key design parametres for audio power amplifiers are gain, noise, frequency response, and distortion. Each parametre is dependent upon another for a steady, powerful signal. Modern digital devices provide a flat signal; therefore, the amplifier is used as a volume and switching control, integrated into a power amplifier. Linear amplifiers are a type of audio power amplifier used in audio equipment, laboratory equipment, and amateur radio. Amplifiers utilised in amateur radio still use the vacuum tube technology, and provide the user 10 to 20 times the radio frequency amplification. The term linearity refers to the ability of the amplifier to produce signals that are accurate copies of the input, normally at higher power levels. The efficiency of this amplifier is affected by power output capabilities, supply voltage, load impedance, and input bias output.

What is a CB Radio Amplifier?

The CB or Citizens’ Band radio comprises a system of short-distance radio communications between individuals utilising a selection of over 40 channels with the 27-MHz band. CB radios are different from other types of amateur radios because CB operation does not require a licence and may be used for both business and personal communication. The use of CB radio in the United Kingdom has grown exponentially since the late 1970s and early 1980s, when small groups were using illegal American CB radios. The British government stated the CB radio would never be legalised on the 27-MHz band; however, in November 1981, 40 frequencies unique to the UK were allocated at 27 MHz, and 20 channels at 934 MHz. At this time, the maximum power allowable was four watts, in order to reduce TV interference. Over the next 25 years, more regulations were relaxed, culminating in the withdrawal of the 934 MHz band in 1998 and the deregulation of CB radio eight years later.

UK regulations governing CB transmissions differ somewhat from those in other countries. AM/FM CB transceivers are legal in Europe, but the use of AM in the UK is illegal. Another main difference is that, while CB amplifiers are legal in the UK, they are illegal in other countries, such as the United States. CB radio use is limited but growing in popularity amongst truckers, mini-cab services, and the farming community. The most widely used channels are the Young Farmers Club found at channel 11, and the normal calling and truckers’ channel found at channel 19.

Factors to Consider When Selecting an Amplifier

There are several factors for consideration when choosing a CB radio amplifier, including gain, bandwidth, efficiency, linearity, noise, and stability. These factors work together to create a clear signal.

Gain

Gain is a measure of the ability of an amplifier to increase the power (amplitude) of a signal when it travels from the input to the output, by adding energy. This term means slightly different things when used to describe operational amplifiers compared to radio frequency amplifiers. Operational amplifiers undergo a voltage gain, while radio frequency amplifiers experience a power gain.

Bandwidth (Signal Processing)

The term ‘bandwidth’ is a widely used term that varies in meaning depending on the field being discussed. When used in reference to amplifiers, bandwidth is the difference between the upper and lower in a set of frequencies. It is measured in hertz (Hz), and may be referred to as passband or baseband bandwidth.

Passband bandwidth is the difference between upper and lower cutoff frequencies, while baseband bandwidth is equivalent to the upper cutoff frequency. A unique characteristic of bandwidth is it can carry the same amount of information, regardless of where it is located on the frequency spectrum.

Efficiency

Amplifier efficiency is a complex concept explaining the mystery of power in versus power out. No electronic device can be completely efficient. Power lost from an amplifier is converted to heat and causes degeneration of sound. The classes of amplifiers available to consumers are designated by letter, which signify their level of efficiency, much the way appliances are rated for electrical consumption.

Class

Efficiency

A

less than 50 %

B

60‒65 %

AB1

~ 65 %

AB2

65‒75 %

C

75 %

Linearity

Linearity is an important performance parametre when choosing a CB radio amplifier. This term is synonymous with fidelity, which is to increase the power level of an input signal without altering its content. The term ‘linearity’ is derived from the amplifier’s relationship of input power with output power, which is related by the gain of the amplifier. Amplifier linearity is preserving the integrity of the complex modulation formats, in conjunction with bandwidth and efficiency, to achieve high data rates of transfer.

Noise

Amplifier noise refers to the signals in the system which are unwanted, leading to degradation of the signal content. An amplifier system divides the noise it receives at its input from the noise it generates itself. A high-quality system is one where the noise generated by the amplifier itself is small compared to noise from incoming sources. Noise in any amplifier system is dependent upon the bandwidth of the system when defining performance.

Stability

Stability is an issue in all amplifiers with feedback, whether intentional or unintentional. If an amplifier has a reflective gain, it is referred to as unstable and will have wild shifts in oscillation. Adding stable elements to the amplifier will create a stable load with no oscillation. This is not considered unconditional stability, because, with a change in load impedance and source, the amplifier may yet break into oscillation.

Power Supply

Power supply is an important factor when choosing a CB radio amplifier. A limiting factor in utilising this device is total input power, which should always be greater than expected output.

The three categories of power supply are: variable gain, broadband, and low noise. Variable gain amplifiers modulate incoming signals along the band from analogue to digital. Broadband amplifiers reproduce signals throughout a passband without loss, and low noise amplifiers have a steady gain over frequency, which improves sensitivity and range.

How to Hook Up a CB Radio Amplifier

When hooking up a CB radio amplifier, it is critical to ensure that the equipment is correctly tuned. If the amplifier is out of tune, it will interfere with all kinds of surrounding radio and TV systems. Amplifiers create an excessive power output if not properly utilised, which can pose a safety risk.

Before hooking up the CB radio amplifier, ensure the SWR reading on the antenna is below a 1.5 ratio. The dead key of the CB radio should be no more than 10 watts, or there is a risk of damage stemming from overheating. Remove the antenna plug from the radio and connect it into the amplifier socket labelled ‘output’. A double-ended patch lead should be connected to the CB radio and connected to the socket labelled ‘input’ on the amplifier. Once all connections are complete, connect the power supply, if applicable.

Buying a CB Radio Amplifier on eBay

When looking to buy CB radio amplifiers from eBay,, there are several specifications to be aware of in order to make the most suitable purchase for your needs. Performing some very basic research first on the make and model of the amplifier you are interested in will reveal what other accessories may be needed in order to hook up your new amplifier. Amplifiers do not all work the same.

Once you have identified the type of amplifier most suitable for your system, enter those specifications as keywords into the search prompt. Keywords such as ‘linear amplifier’, should prove helpful in narrowing down your search.

Before making a purchase, it’s smart to verify that the amplifier you are considering is compatible with your CB radio. This information is readily available in your CB radio’s user manual as well as online. Your CB radio should be designed to handle the power of the amplifier in order to avoid damaging your device.

Conclusion

CB radio amplifiers are an excellent way to increase the span of transmission when utilising a CB radio. When used safely and properly, communication is crystal clear. If used improperly, the amplifier will interfere with neighboring radio and TV signals (which may make neighbors very unhappy).

There are several specifications to look for when purchasing a new or used radio amplifier. As mentioned earlier in this guide, gain, bandwidth, efficiency, linearity, noise, stability, and power supply are all important factors to be aware of and compare. Each factor works in conjunction with the others to create a clear signal for users on both the transmitting and receiving ends.

Before hooking up a CB radio amplifier, ensure all necessary parts and accessories are available, and, most important, that the CB radio is designed to handle the power output of the amplifier. If the radio is not able to handle the output, the user risks distortion and damage to both the radio and amplifier. eBay is an excellent, convenient resource when purchasing an amplifier,, with new and used equipment and accessories widely available. A good rule of thumb when buying online is to always check out top-rated sellers vetted by consumers before making any purchase.

Have something to share, create your own guide... Write a guide
Explore more guides