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Radio Scanner Guide


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Part 8: Using Radio Scanners

1. Banks- Banks are simply groups of channels that can be easily turned on or off at the push of a button. Typically most scanners with 50 or more channels will have 5 or 10 banks.  Banks offer an easy way to group frequencies of a common interest, agency, or location. For example, a listener may program all police and sheriff frequencies into bank 1 and all fire/medical frequencies into bank 2, and all aircraft frequencies into bank 3. When the listener wants to listen to everything, he turns on all banks. If he only wants to hear police, he turns off the other 2 banks. A user who frequency travels between cities may program each bank with frequencies from a different city. When he visits Atlanta, he simply turns on banks containing Atlanta frequencies. When he visits New York, he turns on the correct banks and turns off the banks containing Atlanta frequencies. Virtually all popular scanners allow the listener to turn on any combination of banks at a particular time.

2. Trunking Scanners - Trunking or "trunk-tracking" scanners contain special circuitry that listens to the control channel in order to detect what frequencies are in use for each active talkgroup. For an introduction to trunking, read Part 3A: Land Mobile Services. Most trunking scanners, like other scanners, typically have their channels divided into 5, 10, or more banks. In most trunking scanners, you may program one trunked system into each bank. In newer scanners, you only need to program the control channel frequencies into the scanner for Motorola systems. However, with older trunking scanners or when monitoring non-Motorola systems (EDACS or LTR) you must program all system frequencies. Newer scanners also allow conventional (non-trunked) frequencies into the same bank with a trunked system. Also, most newer radios allow the user to listen to multiple trunked systems at the same time.

3. Using "Scan Lists or "Sub-banks" - Trunking scanners come with a certain number of talkgroup ID memories ("ID's") allocated to each bank to store the ID's of talkgroups you wish to monitor. These ID's can be organized into 5 or 10 "sub-banks", also called "Scan Lists", each of which contains 10-30 ID's. Typically, you will want to put Talkgroup ID's of similar agencies or purposes into the same bank. When monitoring a county's trunked system , you may put the Sheriff's talkgroups into one sub-bank, the fire/medical department into another, and other local services into a third sub-bank. While monitoring the trunked system, you may choose which sub-banks are activated so that you will only hear those talkgroups. Your scanner's user manual will contain more detailed instructions including the number of channels, banks, talkgroup ID memories, and sub-banks your scanner contains. You may download an online user manual for your radio scanner by using the links in Part 9: Where to find more information.

4. Bandwidth - The width of frequency space each channel occupies is referred to as "bandwidth". Example: One FM station may be on 100.1 FM. The next channel would be 100.3 FM. Therefore the bandwidth, or the width of each station, would be 0.2 MHz. 2-way radio channels like those used by police and fire departments are closer together. For example 154.665; 154.680; 154.695 are 3 channels available for police use. These channels have a bandwidth of 0.015 MHz, or 5 kHz. Sometimes if a station sounds weak, your scanner radio may be tuning it off-center. For example, a scanner receives a station on 154.700 MHz. The station is actually centered around 154.695 MHz, with portions of the signal between 154.685 to 154.705 MHz. The scanner is only receiving about half of the signal due to this off-center reception. In this case, reprogramming the correct frequency will solve the problem.

5. Mode and Step Selection - Two methods for carrying voice and data over radio frequencies are Amplitude Modulation (AM) and Frequency Modulation. AM similar to that used on commercial AM radio. It has no immunity to static but narrow bandwidth. Wide FM (WFM) is used on commercial broadcast FM radio. It features good immunity to interference and good sound quality, yet has a wide bandwidth. The type of FM used on scanner frequencies has a narrower bandwidth than commercial FM broadcast radio in order to allow closer channel spacing. In the US, almost all services except aircraft use narrow FM. Civil and military aircraft both use AM. Scanners will choose the correct mode for each frequency so the user does not need to worry. occasionally a radio signal will be in a non-standard mode (AM on an NFM band, or vice-versa). If a signal is distorted or the voice volume is very low, try changing the mode on your scanner if mode selection is available. Scanners designed to receive commercial FM broadcast radio and TV sound can receive all three modes - AM, NFM, and WFM - and often allow the user to manually override the default mode selection.

When searching for new frequencies, scanners will choose the most common channel spacing (search step size) for that particular radio band.  However, some transmissions may use a different channel spacing.  Some high-end scanners will allow the use to override the automatic step selection and choose the frequency step size needed.  All "Category 6: Continuous Coverage" Radio Scanners allow both mode and step selection.  These radios will automatically default to using the most common mode and step for the radio band, but then allow the user to override the mode and step.  Most other radio scanners do not allow the use to choose the mode or search step size unless otherwise indicated.  

Part 7: Scanner Accessories
Part 9: More Information


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