Radio Scanner Guide
Part 5: Radio Scanner Features
The following are some features and criteria you should take into account when purchasing your radio scanner.
Handheld scanners are more flexible, and if you prefer the flexibility of being able to take your radio with you when traveling, going to races and other sporting events, or even while walking around your house, I would recommend you purchase a handheld. Scanner listeners who only monitor from one fixed location though, will probably enjoy the minor benefits of a base receiver. Both types of receivers are listed in each category of this guide.
2. Number of Channels - The number of scanner channels determines how many agencies and systems you can monitor. Having a scanner with many channels allow you to avoid having to reprogram the radio every time you wish to monitor a new agency, then have to program the original frequencies again. If you are only interested in one agency, such as a local police or sheriff's department, 10 or 20 channels may be enough. If you would like the flexibility to listen to multiple agencies, including police and fire departments from multiple jurisdictions and news media, buy a scanner with more channels. In a medium or large metro area, often each incorporated city and suburb will have their own departments - in addition to county and state law enforcement and emergency services. Often each department will have 5 or 10 frequencies. Urban listeners will usually want the most channels, but even many rural listeners will want a radio from Category 2 or higher. It's easy for an experienced listener to fill up 200, 500, or even 1000 frequencies.
3. Number of Banks - In a scanner with a large number of channels, the channels are usually organized into groups known as banks. The user will program all frequencies for a common topic, such as law enforcement, into one bank. All Fire/Medical frequencies would go in another, all aircraft frequencies into a third banks. The listener may turn banks on or off at any time when he or she wants to listen to a particular agency. Most of the time, a listener will not want to listen to every agency programmed in his or her radio, but rather would like the ability to turn on that agency's bank with the push of a button.
Banks contain a fixed number of channels, chosen at the factory. On the other hand, scanners with Dynamic Memory Allocation feature Scan Lists. Scan Lists are like banks, except that the number of channels in each Scan List can be changed at any time.
4. Search Mode - A search mode allows you to search for radio systems on new or unknown frequencies/channels. The frequencies and channel arrangements for many exciting agencies cannot be found in most frequency books, particularly if they are unlicensed, new, or simply not published. Virtually all federal government agencies, such as NASA, the FBI, and the US Park Service are not published but can be found by curious listeners using the search mode. Search modes are found on all but the least capable scanners, including many inexpensive scanners selling on eBay, and are highly recommended. All Category 2,3,4,5, and 6 scanners in this guide have at least one type of search mode.
Types of Search Modes: Limit Search, the most common type of search mode, allows you to search between 2 user-defined search limits. Direct Search starts a search from a currently-displayed frequency without having to program search limits and is good for quick searches. Band Search searches a pre-determined radio band is therefore less useful than the other types. The "Search Lockout" feature allows you to "lock-out" or delete a frequency when performing a search. This feature allows you to repeatedly search a radio band without stopping each time on a busy channel or a frequency with constant interference.
5. Scan and Search Speed - Your scanner's scan speed is a measure of how many channels it scans through each second while search speed measures how many frequency "steps" are searched each second. High scan and search speeds are important when scanning many channels at one time or searching a large radio band.
For general use, look for a scanning speed of at least 25 channels per second and a search speed of at least 50 channels per second. A high scan speed is especially important for scanning a bank of "mystery" frequencies that are rarely active while scanning a normal group of active frequencies. This way you can continually scan the active stations without missing replies while also checking the group of "mystery" frequencies. Search speed is especially important when scanning a large radio band with few active stations. Above the speeds given above, scan and search speed becomes less important. A scanning speed of 16 channels per second should be adequate for listening to 10 or more channels; the vast majority of scanners meet this requirement. 25 Channels per second is good, while 50 is excellent. For search speeds, 50 is good, while 100 or higher is excellent.
6. Service Search - Service Search, also known as Service Scan, is a feature that allows the user to scan a set of preprogrammed frequencies for a particular radio service. Many modern scanners, particularly those designed for mobile and handheld use, include preprogrammed Service Search options for Police, Fire/Medical, Aircraft, and Marine. It should be noted that since frequency use varies by community, these preprogrammed frequencies might not include the desired service in your area. Yet they likely will also include numerous unwanted transmissions. Service Search can be useful, especially when traveling to a new city, but is not a substitute for programming your own radio with local frequencies.
9. Mode and Step Selection - Mode selection allows the user to manually select the receive mode, usually between Narrow FM (NFM), AM, Wide FM (WFM) and various trunking modes. While most scanners will automatically select the correct mode for each frequency, there are cases where the user will need to manually override that decision. Step selection allows the user to override the scanner's automatic search step selection and is useful for monitoring stations that use unusual channel spacing. Both features are found mainly in radios in Category 6: Continuous Coverage Scanners.
10. Sensitivity - Sensitivity is a measure of the signal strength required to hear a station. It is measured in microvolts (uV). A smaller number indicates a more sensitive receiver since less signal strength is needed to hear the station. Sensitivity is primarily of importance in rural areas or when listening to weak-signal transmissions such as military aircraft.
11. Selectivity - -Selectivity is the ability to select a station on one frequency from another on an adjacent frequency. Selectivity is primarily of importance in urban areas, where strong signals are very common.
12. Computer Control - Some scanners feature the ability to have frequencies downloaded to them. Others also allow a computer to operate most the scanner radio's functions.
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