Scanner Frequently Asked Questions
Section 1 - Scanner Basics

What is a scanner and why would I want / need one?

What different types of scanners are available?

What can I legally listen to?

What accessories are available to improve my scanning?

A broadcaster in my area now uses a digital system; why can't I find a digital scanner?

What are birdies?

Reception Notes

General Troubleshooting

A Guide To The Action Bands

A Guide To Frequencies National Weather Frequencies Ham Radio Frequencies Citizens Band United States Broadcast Bands International Broadcast Bands

Typical and Primary Band Usage, and Specified Intervals

Band Allocation

Frequency Conversion

Image Reception

Additional On-line Information

Glossary

What is a scanner and why would I want / need one?

A scanner is a radio receiver designed to allow you to listen to radio transmissions from the various agencies and companies using radio communications in your area, such as police and fire departments, ambulance services, government agencies, air, and amateur radio services. Scanners let you scan these transmissions and are often preprogrammed with service search banks for convenience. By pressing a single button, you can quickly search those frequencies most commonly used by public service and other agencies without tedious and complicated programming. Scanning is a growing hobby that lets you "listen in" on public radio conversations and keep up on current local events as they are happening.

What different types of scanners are available?

Scanners are broken down by physical types and scanning methods.

The three physical types of scanners are Handheld, Mobile and Desktop. The primary differences between them are shown in the table below. Range is dependent on the antenna used, and a handheld scanner can usually be used in a mobile or desktop environment by attaching it to a vehicle-mounted or base-station antenna (see Scanner Antennas and Other Accessories).

The three basic scanning methods are Crystal-controlled, Conventional Programmable and Trunk Tracking Programmable.

Early scanners were crystal-controlled. These scanners had one or more internal slots for a crystal which allowed the radio to receive a single frequency. Crystal-controlled scanners are not currently being sold. However, a number of them turn up in pawn shops and garage sales. For example, the PRO-25 (Cat. No. 200-0106), PRO-27 (Cat. No. 200-0108), and PRO-53 (Cat. No. 200-0122) scanners were of this type. Generally, if you are looking at a RadioShack scanner and it does not have a keypad or program button, it is probably crystal-controlled. The disadvantage of crystal-controlled scanners is that they were slow to tune, expensive to set-up for new frequency/channel activity, and they can not follow the new trunked radio activity.

In the mid-80's, programmable scanners were introduced. These use integrated circuits to allow the radio to tune to a range of frequencies and were a marked improvement over crystal-controlled scanners, which required the purchase and installation of different crystals. Programmable scanners come with a wide range of features and capabilities and are distinguished from one another by the following features:

• The number of channels
• The frequency ranges they can pick up
• Frequency band and/or service band search
• Scan speed (channels per second and/or steps per second)
• Whether they are conventional or trunking

Conventional Programmable Scanners:

Trunking Programmable Scanners:

The newest innovation in scanners is Trunking Scanners. Trunking scanners are designed to track Motorola^® Type I and Type II (such as Smartnet™ and Privacy Plus™) and hybrid analog trunking systems, plus GE/Ericsson (EDACS^®) and EF Johnson^® (LTR^®) type systems, which are extensively used in many communication systems. Trunking communications systems let a large group of 2-way radio users (or even different groups of 2-way radio users) efficiently use a set of frequencies. Instead of selecting a specific frequency for a transmission, the user simply selects a talk group. The trunking system automatically transmits the call on the first available frequency, and also sends a code that uniquely identifies that transmission. Since the trunking system might send a call and its response on different frequencies, it is difficult to listen to trunked communications using a regular scanner. Trunking scanners monitor the data sent with a 2-way radio transmission so you can hear the call and response for that user and more easily "follow" the conversation.

What can I legally listen to?

You can hear police and fire departments, ambulance services, government agencies, private companies, amateur radio services, aircraft, and military operations. It is legal to listen to almost every transmission your scanner can receive. However, there are some electronic and wire communications that are illegal to intentionally intercept. These include: telephone conversations (cellular, cordless, or other private means of telephone signal transmission), pager transmissions, and scrambled or encrypted transmissions. According to the Federal Electronic Communications Privacy Act (ECPA), as amended, you could be fined and possibly imprisoned for intentionally listening to, using, or disclosing the contents of such a transmission unless you have the consent of a party to the communication (unless such activity is otherwise illegal). These laws change from time to time and there might be state or local laws that also affect legal scanner usage.

What accessories are available to improve my scanning?

We offer several accessories for our scanners, such as noise-blocking headphones, antenna mounts and antennas.

Headphones

Antenna Mounts

Clip-On Antenna Mount (Cat. No. 20-023) Product Features: Window clip mounts antenna on glass Works with scanner or handy-talkie flex antennas For car, home, and travel 6 foot cord with BNC plug   Back to Top Back to Main Index

Antennas for Base Stations

Outdoor Scanner/Ham Discone Antenna (Cat. No. 20-043) Product Features: Omnidirectional, rugged stainless steel construction Wide 25 - 1300 MHz receive coverage Transmits on 50, 144, 220, 440, 900 and 1296 MHz Ham bands Resonator and tunable whip for best 50 MHz performance About 44" high, overall Fits mast up to 1" in diameter Accepts PL-259 connector (Use plug adapter 278-117 for scanners that have BNC connector)   Back to Top Back to Main Index
Outdoor VHF-Hi/UHF Scanner Antenna (Cat. No. 20-176) Product Features: Chrome-plated brass vertical element Covers 108 to 1300 MHz with peak performance in 152-470 MHz About 20" high Accepts PL-259 connector (Use plug adapter 278-117 for scanners that have BNC connector)   Back to Top Back to Main Index
Indoor Scanner Antenna (Cat. No. 20-161) Product Features: Covers 30 to 512MHz Extends to 40" Accepts PL-259 connector (Use plug adapter 278-117 for scanners that have BNC connector)   Back to Top Back to Main Index

Antennas for Mobile Stations

Magnet-Mount Mobile Scanner Antenna (Cat. No. 20-032) Product Features: Covers 25 to 1300 MHz About 36" high Includes 16 foot cable with BNC type adapter connector Note: Magnetic-mount antennas are not recommended for use on vinyl roofs.   Back to Top Back to Main Index
Mobile "Cellular Look-Alike" Glass-Mount Scanner Antenna (Cat. No.20-011) Product Features: No holes to drill. Easily installs on windshield or window. Covers 25 to 1300 MHz 22"-high element Includes 16-foot cable with BNC connector.   Back to Top Back to Main Index

Antennas for Handheld Stations

Deluxe Antenna for Handheld Scanner (Cat. No. 20-034) Product Features: Longer 9" length helps improve reception of marginal signals BNC connector fits all RadioShack and most other handheld scanners Can also be used with Ham HT's for transmitting on the 144 MHz or 440 MHz Ham bands.   Back to Top Back to Main Index
Center-Loaded Telescoping Whip Antenna (Cat. No. 20-006) Product Features: Receives 25 to 1300MHz Transmits on 144 MHz, 220 MHz and 440MHz Ham bands Nine sections   Back to Top Back to Main Index

A broadcaster in my area now uses a digital system; why can't I find a digital scanner?

Currently, most radio systems are analog systems; however, some areas have begun using digital radio systems. At this time, all of our scanners are analog only; we do not currently sell a digital scanner.

What are birdies?

Birdies are frequencies your scanner uses when it operates. These operating frequencies might interfere with broadcasts on the same frequencies. If you program one of these frequencies, you will hear only noise on that frequency. If the interference is not severe, you might be able to turn up the squelch to cut out the birdie. The most common birdies to watch for are listed below.

Birdie Frequencies

You can use the following procedure to check for birdies in your particular scanner.

1. Remove the antenna.
2. Turn the scanner on and set up a limit search for all bands on the scanner.
3. Be sure that the scanner is separated from possible signal sources such as a PC, other transceivers, etc.
4. Write down the frequencies where the scan stops or detects a continuous noise signal. These are the Birdies.

Reception Notes

Reception of the frequencies covered by your scanner is mainly "line of sight". That means you usually cannot hear stations that are beyond the horizon. During the summer months you may be able to hear stations in the 30-50 MHz range located several hundred or even thousands of miles away. This is because of summer atmospheric conditions. This type of reception is unpredictable but often very interesting! One very useful service is the National Weather Service's continuous weather broadcast. These broadcasts contain weather forecasts and data for the areas around the station, plus bulletins on any threatening weather conditions. These stations use several frequencies; and in most areas of the country, you can receive one of these frequencies.

General Troubleshooting

Check that you are following the correct steps per the manual.

Check the frequency to be sure you are entering it correctly.

Check the scanner's frequency coverage to be sure that the scanner can receive that frequency.

Check the scanner's reception ability by programming a known continuous voice broadcast such as NOAA on 162.4Mhz – 162.55Mhz.

You can do this by going to the Weather service band (if available on your scanner) or by programming a limit search from 160Mhz – 170Mhz.

Reset the scanner as a last resort; this erases all memory contents and resets the radio back to factory settings. The reset for most RadioShack scanners is given below; however, for some models there is no reset and the only way to reset the scanner is to remove power.

1. Turn the scanner off.
2. Push the 2 and 9 buttons and hold them down.
3. Turn the scanner on while holding down the buttons.
4. Release the 2 and 9 after the display shows CLEAR.

A Guide To The Action Bands

With the right frequencies programmed into your scanner, you can monitor exciting events. With a little investigation, you can find active frequencies in your community. We can give you some general pointers, and you can take it from there. Please use caution and common sense when you hear an emergency call. Never go to the scene of an emergency. It could be very dangerous. Find out if there is a local club that monitors your community's frequencies. Perhaps a local electronics repair shop that works on equipment similar to your scanner can give you frequencies used by local radio services. A volunteer police department or fire department can also be a good source for this information.

As a general rule on VHF, most activity is concentrated between 153.785 and 155.98 MHz and then again from 158.73 to 159.46 MHz. Here you find local government, police, fire and most such emergency services. If you are near a railroad yard or major railroad tracks, look around 160.0 to 161.9 MHz for signals.

In some larger cities, there has been a move to the UHF bands for emergency service. Here, most of the activity is between 453.025 and 453.95 MHz and between 456.025 and 467.925 MHz.

In the UHF band, frequencies between 456.025 and 459.95 MHz and between 465.025 and 469.975 MHz are used by mobile units and control stations associated with base and repeater units that operate 5 MHz lower (that is, 451.025 to 454.950 and 460.025 to 464.975 MHz). This means that if you find an active frequency inside one of these spreads, you can look 5 MHz lower (or higher) to find the base station/repeater for that service.

Typical Band Usage

The following is a brief listing of the typical services that use bands that a scanner can receive. This listing helps you decide which ranges you would like to scan. These frequencies are subject to change, and might vary from area to area. For a more complete listing refer to the Police Call Radio Guide available at your local RadioShack store.

Abbreviations

Attention: Your scanner may not be able to receive all frequencies and/or modes of reception that are contained within this document. For complete information of your scanner's capabilities, be sure to read your owner's manual completely.

A Guide To Frequencies

• National Weather Frequencies
• Ham Radio Frequencies
• Citizens Band
• United States Broadcast Bands
• International Broadcast Bands

National Weather Frequencies

Ham Radio Frequencies

Ham operators often transmit emergency information when other communication methods break down. The following chart shows some of the frequencies that Hams use.

Citizens Band

United States Broadcast Bands

In the United States, there are several broadcast bands. The standard AM and FM bands are probably the most well known. There are also four television audio broadcast bands -- the lower three transmit on the VHF band and the fourth transmits on the UHF band.

Frequency Range Allocation

International Broadcast Bands

Several short-wave bands are allocated for international broadcasting because of the nature of propagation of high frequencies. The bands are sometimes identified according to the approximate wavelength of the signals in meters. Your scanner may receive the 11-meter band, from 25.6 - 26.10 MHz.

Typical and Primary Band Usage, and Specified Intervals

Typical Band Usage

Primary Usage

As a general rule, most of the radio activity is concentrated on the following frequencies:

Note: UHF remote control stations and mobile units typically operate at 5 MHz higher than their associated base and relay repeater units.

Specified Intervals

Frequencies in different bands are accessible only at specific intervals. For example:

Note: Your scanner rounds the entered frequency to the nearest valid frequency. For example, if you try to enter 151.473, the scanner might accept this as 151.470.

Band Allocation

To help you decide which frequency ranges to search, use the following listing of the typical services that use the frequencies your scanner receives. These frequencies are subject to change, and might vary from area to area. For a more complete listing, refer to the "Police-Call Radio Guide including Fire and Emergency Services", as well as "Beyond Police Call", "Aeronautical Directory", "Nautical Directory" and "Now you're Talking" texts available at your local RadioShack store.

Abbreviations

Frequency Bands

High Frequency (HF) - (3 - 30 MHz)

Very High Frequency (VHF) - (30 - 300 MHz)

Ultra High Frequency (UHF) - (300 MHz - 3 GHz)

Note: Some cities use the 470 - 512 MHz band for land/mobile service.

Frequency Conversion

The tuning of a station can be expressed in frequency (kHz or MHz) or in wavelength (meters). The following information can help you make the necessary conversions.

• 1 MHz (million) = 1,000 kHz (thousand)

To convert MHz to kHz, multiply by 1,000:

• 9.62 MHz x 1000 = 9620 kHz

To convert from kHz to MHz, divide by 1,000

• 2780 kHz / 1000 = 2.780 MHz

To convert MHz to meters, divide 300 by the number of megahertz

• 300 / 7.1 MHz = 42.25 meters

Image Reception

Radios work by simple mathematics. For example, most tune to a frequency by mixing that frequency with another (local oscillator) frequency which is slightly different. This mixing process primarily gives us the two original frequencies, their sum, and their difference. Well, the radio's Intermediate Frequency (IF) filter normally passes either the sum or difference frequency, and this is then processed into the sound we hear. Because nothing is perfect, certain "harmonics" will also get through if they are strong enough. For example, if a radio's IF is 10.7 MHz, we might be able to tune to a frequency 21.4 MHz (2 x IF) above (or below, depending on the radio's design) a strong signal and hear it! This is more evident in a dual-conversion radio than a triple-conversion radio, because the triple-conversion radio's 1st intermediate frequency is quite high. This causes the image to be so far off frequency that it is easy to effectively filter it out.

Just because a radio doesn't receive something which another does is not necessarily an indication of a problem. The one radio may simply not be "tricked" into picking up an image! This rejection of undesired signals is one reason that a triple-conversion receiver costs more than a similar dual-conversion model. If you are more interested in finding more out about radios and radio operation, a good location to start looking is your local public library. You might also wish to contact the ARRL, as they are an excellent source of informative texts on the subject.

Additional On-line Information

Glossary

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