Communications – CB Radio Basics

CB Radio Basics

 

There are dozens of makes and models of CB Radios, but they all have basically the same general form, just differing in the ‘bells & whistles’ department. A simplified breakdown of what’s inside that box you just bought for the car is:

  • A transmitter with a handheld microphone
  • A receiver with a speaker
  • Connections for power, antenna, and any accessories.

Wipe away all the gee-whiz features on your radio, and this is what they all consist of. Simple, huh?

Very. So learning to use your radio is quite simple, too. Here are some basic operating tips that will have you operating like a pro in no time, if you think in terms of these basics:

TRANSMITTING
  • ALWAYS listen for a moment before starting to transmit for the first time on a channel. You may be interfering with a QSO in progress. If the channel is busy, ask for a “break” if you need to use the frequency or join the conversation.
  • Make sure you use channels for their accepted uses. Yes, the only channel with a specific use by regs is Ch. 09. However, years of CB use has set up unofficial territories in the CB band by various groups. For instance, Ch. 19 is the most used channel for truck drivers around the country, but there are others. And Sideband (SSB) operators have several channels they try to warn AM-CBers off of, because the carrier signal from AM transmissions causes interference with the weak signals that SSB is capable of hearing. See the frequency list above for notes on channels that commonly have special uses, and follow those uses, unless you just WANT to be rude.
  • Try to stay away from sounding like you just climbed out of a “Smokey and the Bandit” rerun. There are a few old timers who can make the Good Ol’ Boy accent sound good, but you’ll find most CB’ers just talk in a normal voice.
  • Don’t eat your microphone. Talking too close and/or too loud is the most common boo-boo new CBers make, often with the mistaken impression that being louder translates to talking farther. From a technical standpoint (under controlled conditions) this is true, but what good does it do to have your signal go an extra 1/4 mile, if your voice is so garbled no one can understand what you said? Another important microphone habit is to use careful keying of your microphone. Push in the key, wait a short moment, then talk. And make sure you are done talking, then wait again, before un-keying. New CB’ers are often spotted by the way they cut off the beginning or ending of what they say, by bad keying. Keying is important in another way, too. Many new operators assume CB is like a telephone, where you can talk and be heard at the same time. There are radio services like this, using what is called Duplex operation. CB is not one of them. If you key your microphone to talk while your friend is still flapping his jaws, both of you are going to miss part of the conversation, because you have to take turns on CB.
RECEPTION
  • Adjust your volume and squelch properly. Having the squelch control too high is an easy way to miss transmissions. Having it too low is an easy way to get a headache from static or skip interference. Same goes for proper volume settings, though in reverse effect. Ideally, you should set your volume first (squelch all the way off) while listening to chatter on the channel. Then adjust the squelch control up to the point where it just cuts the background noise, but no more.
  • RF Gain, Fine Tuning, and Tone Controls can be your friends. If you have a radio with any of these features, they can do wonders for listening when there is a lot of man-made or natural interference. Get to know how they work, and use them whenever needed.
  • If you are working weak signals (common in skip-shooting or DXing) consider using headphones. Even slight background noises around you can disturb you enough that signals easily heard with headphones are unreadable without them.
  • When first starting out and trying to get the hang of talking on your radio, spend a few days just listening. The “Trucker” stereotype CBer from the movies doesn’t exist in a lot of places, and you’ll sound like an idiot if you try to sound like one. Most areas of the country have their own style – listen to it and learn it if you want to fit in rather than stand out and be ridiculed.
CONNECTIONS
  • NEVER operate your radio with the antenna disconnected. This can damage the transmitter circuitry and render your radio useless. There are some radios that have high-tolerance circuitry that will handle having a badly tuned or disconnected antenna, and even some models that have a protection circuit built in that cuts off the transmitter if it detects a bad antenna hookup. But most CB’s are not set up for this. Unless you are certain you have a protected model, don’t try it.
  • Probably the biggest improvement or degrade to your radio that you can make is your antenna tuning. A poorly tuned antenna acts like a reflective surface does to light – it will reflect your transmitter power back to the radio. This not only cuts your range, but can damage the radio if the reflected amount of power is high enough.
  • Always use a fuse in your power connection. I’ve “inherited” dozens of radios from friends who ignored this advice and fried a radio because of reversed connections, short circuits, etc. People like this help the finances of radio repairmen by supplying easily fixed and resold radios with blown power input components. But for those who don’t have the know-how to fix such a screwup, the radio is just fried, as far as they are concerned – it’s often cheaper to buy a new one than pay to fix it, because of the labor cost. But if you’d rather buy a new $50 – $150 radio instead of a 25 cent fuse….

There are also different styles of CB radios to choose from, but fortunately these can be broken down into simple groups as well. Each has its special use that it was well designed for:

MOBILE A radio designed for use in an auto or other vehicle. Usually has a compact size case and handheld microphone, and is powered by 12 volts from the vehicle’s battery. Mobile radios are designed more for on-the-road convenience than quality of use, except for the high-end models. Even the high cost models often have poor audio quality compared to many base stations. But the features of a quality mobile radio make it ideal for it’s working environment – noise canceling microphone circuitry, back-lit controls, compact size, multiple-use controls, etc. all help a mobile perform in situations where a Base Station would be inconvenient or even useless. These radios utilize a downsized antenna mounted on the vehicle, connected with coaxial cable to the radio.
BASE STATION A radio designed for home or fixed location use. Usually has a large, desktop style case, even though the radio circuitry inside is often the exact same circuit board used in the mobile unit. Chief advantages in use quality for a Base Station are a bigger speaker for more receiving clarity, and larger meters and controls for easier operations. Base Stations are powered by house current, but often have a second power input that uses 12 volts from a car battery – these radios are often called Base/Mobiles in advertisements. Dual power makes this type of Base Station popular for RV owners and survival types who have battery backup to use the radio if house current disappears. Base Stations typically use a desk top stand-alone microphone, and a high efficiency rooftop antenna connected with coaxial cable to the radio.
PORTABLE Also called Handhelds or Walkie-talkies. Electronic miniaturization has come a long way since the 70’s. Where CB Portables used to operate with just a few channels and be as big as a brick (and about that heavy) you can get 40 channel handheld CB’s now that are only a little bigger than a cell phone, often with full power output. Handheld radios usually have the microphone and antenna built into the radio, but some models have provisions for external hookups of power, microphones, earphones, and antenna jack.

 

If you just plan to buy and operate a standard CB for general communications, don’t worry about any of the following information!However….if you plan to get into the hobbyist aspect of CB, there are some idiosyncrasies about the 3 different transmission modes in use on CB bands that you should be aware of.

 

A final, but very important point for those who are looking for more than BASIC CB OPERATION concerns TRANSMISSION MODE (how your voice is sent). The way you operate your radio with each mode is a completely different world from any other mode. Of all the aspects of CB use, this is the place you are most likely to be concerned with the technical details of how things work. So first, let’s get a few important definitions out of the way:

  • FREQUENCY: usually expressed as Megahertz (Mhz) for CB. This is the exact spot on the spectrum where your radio is broadcasting. For reference, if you listen to a station on your portable AM radio that is at 1200 on the dial, this is 1200 kHz, or a frequency of 1.2Mhz. If you listen to an FM Radio station at 102.5 on the dial, this is a frequency of 102.5 Mhz. CB channels are located in the 27 Mhz band (see chart above)
  • MODULATION: this is the voice information that travels in your radio signal. The amount of modulation is usually expressed as a percentage amount, and usually refers to the peak percentage, since your voice varies in loudness as you talk, and so does the modulation amount.
  • CARRIER SIGNAL: This is the basic component of your radio signal, or what gets sent out when you transmit, even without any voice information along with it. Your basic power level and frequency determine how strongly and where at on the radio dial your radio is heard by others.
  • TRANSMISSION MODE: The transmission mode determines the method that your modulation “voice information” is sent with the carrier signal.
  • AMPLITUDE: The basic power level of your signal. There are many factors that can vary this amount of power on a CB Radio signal.
  • BANDWIDTH: This is the amount of frequency space your signal uses up to carry its voice information. The wider the bandwidth, the more information (sound quality) the signal can carry. However, the narrower the bandwidth is, the farther the signal can travel without becoming distorted or garbled.

Here is some basic, simplified information on the technical differences, operation tips, and plus/minus points about each type of transmission mode:

AM AMPLITUDE MODULATION: This is the “standard” transmission mode for CB. If you buy any US made CB, this mode is the one it was primarily designed to use, and unless it comes with the extra option of using other modes, AM is the only mode it can transmit in. Basically, the transmitter in the radio sends out a carrier signal that is amplified in strength by the amount of modulation present on the signal, to a maximum of 4 watts output. This type of signal has what we will call a “medium” bandwidth, in comparison to the other modes, for a good quality audio signal.This mode of transmitting uses the modulation percentage to vary the amplitude (power) of the signal, which means that the “louder” your voice is, the more power your signal has. There are ups and downs to this fact – because your voice has it’s ups and downs as you talk. Many CB radios have built in circuits that limit the amount of power you can put into your voice signal, known as clipping circuits (by FCC regulations, 100% modulation is the maximum allowed on CB). If you exceed the limit of your radio’s circuitry, your voice becomes distorted because the peak (most loud) portions will be clipped off the signal, so it does no good to make your signal stronger by boosting modulation too much. But technology is a wonderful thing if used properly. You can buy Amplified Microphones (known as Power Mikes to most) that can amplify your overall voice level and with enough control so that you can increase your modulation to the perfect level for the best signal. Some radios also have voice compression circuits which squeeze your modulation envelope so that the MAXIMUM modulation percentage stays below the clipping level, but the AVERAGE level stays much higher, which can boost your average signal level in the process.How AM CB stacks up:

 

    Pluses:

    • Cheap/easy circuit to produce, tune, and use
    • Decent quality audio signal
    • Increasing modulation strength and compression can give good improvement in signal strength.

 

    Minuses:

    • Easily affected by atmospheric static, spark plug and other engine noises
    • Wider bandwidth means long distance “skip” transmissions are more easily garbled, requiring stronger signals to get through readably, especially in heavy interference or noise.

 

FM FREQUENCY MODULATION: This mode of transmitting uses the modulation percentage to vary the transmitted frequency of the signal slightly, which keeps the carrier signal amplitude very stable. Because this increases the bandwidth of the signal greatly, it increases the sound quality potential as well. In addition, since nearly all natural noise (static) is Amplitude Modulated, FM mode is virtually free of any noise – all of which adds up to sounding very nice on a radio – and that’s why it’s preferred by your local DJ for broadcasting the latest top-40 tunes. But the increased bandwidth exceeds the amount allowed by the FCC for this band, so FM mode is illegal in the US for CB’s. The only radios you will find with FM capability are foreign made “import” models which are supposed to be illegal for sale here, but somehow still manage to get in to various distributors. Even if you get your hands on one, however, you’ll still find it pretty useless, as anyone you want to talk with has to have an FM-CB radio as well – and they are very few and far between in the US.How FM CB stacks up:

    Pluses:

    • Virtually unaffected by atmospheric static, spark plug and other engine noises
    • Excellent quality audio signal
    • Signal strength stable at all modulation levels.
    Minuses:

    • Very little use in USA due to being illegal and lack of available equipment
    • Complex, expensive circuit to produce and tune, although using FM is relatively trouble free with a properly designed radio.
    • Very wide bandwidth means long distance “skip” transmissions are very easily garbled, requiring strong signals to get through readably
SSB SINGLE SIDEBAND: When standard CB radios broadcast in AM mode, the signal sent out is actually in 3 parts: a carrier signal and two “side bands” that hold the voice information, which helps give the signal a better audio depth. What a Single Sideband (SSB) capable CB radio does is to sacrifice some of the depth (voices sent this way are not full audio range) and compresses your 3 part signal into a single sideband (either the upper (USB) or lower sideband (LSB), depending on which you select). In the process of doing this it removes the carrier and the unused sideband.This has several advantages, all in the increased-range department. First, the reception is better, because the signal is much narrower-band, making it easier to fine tune through noise and interference and less susceptible to distortion or garbling over long distances. SSB receiver circuitry is also more sensitive usually by a factor of at least 3 times better. Last, but definitely not least, the compressing of the 3 part signal into one part effectively compresses the 4 watts that were in each part into the single sideband, giving you 12 watts of output!What this translates to is that your range is much, much better in SSB mode – 10-20 miles is not unusual, and 40 miles talks between base stations can be done in good conditions. But it gets better! Because the signal is so narrow band, it tends to ‘skip’ with much less garbling than a standard AM-CB radio signal. This means that in the right sunspot skip conditions, a SSB radio can be used to talk with stations hundreds or even thousands of miles away, the same way Ham operators do. And many people do.

The only caveat to this form of communication is that the people using it have to have the right equipment – on both ends. If you try to listen to a SSB CB radio with a standard AM-type CB, all the transmissions will sound garbled beyond recognition and Donald-Duck-like. If you use a SSB radio to talk, the party you are communicating with has to use one to listen to you, as well (but be aware that all SSB capable CB’s can switch to use standard AM-CB mode as well, so they can be used for both purposes).

How SSB CB stacks up:

 

    Pluses:

    • Narrow bandwidth means transmissions easily travel long distances with low power and “skip” with minimal distortion, making them excellent for long distance (DX) communications
    • Extra receiver sensitivity and tripled power output give many times the range of AM or FM mode.
    • Improving modulation quality creates drastic improvements in signal strength, since entire signal is audio driven in this mode (no carrier signal)
    • In general, a more ‘professional’ sounding crowd operates on SSB, many are either Ham operators or studying to be. SSB people tend to be more hobbyists than casual talkers.

 

    Minuses:

    • Very little use compared to AM CB due to more expertise required to operate – this is actually a “plus”, because this means fewer loud mouthed half-wits are on SSB, since it takes someone with a brain to operate the radio correctly
    • More complex circuitry to produce and tune adds to radio cost
    • Narrow band signal requires careful fine tuning, more fuss than just channel-clicking as on AM or FM CB
    • Poor quality audio signal (voices have “tinny” sound, although this actually is a another “plus” for it gives better readability in noisy circumstances)

 

 

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