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Selecting a Scanner


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Scanners are much different than other consumer-level radios----or even shortwave radios, for that matter. If you're looking to buy your first scanner radio, you probably feel a bit confused and overwhelmed by the features and specifications of the models you're considering!

As with most consumer items, there is no one "best" scanner radio for everyone. For example, if you want to simply listen to your local police and fire departments, a basic, low cost scanner will do fine. On the other hand, you can easily spent over $1000 for a scanner capable of high performance over a broad frequency range in a variety of modes.

 

General Considerations

The first thing you need to consider about any scanner is what frequency ranges you're interested in monitoring. To get a better idea of what can be heard on different ranges, click here to visit The World About 30 MHz section of this site.

Portable scanners have become popular recently. Some are small enough to fit into a shirt pocket and let you follow the action at sporting events, exhibitions, shows, accident scenes, etc. However, a portable scanner will usually cost more than a home (or "base") unit of comparable features and performance. And remember that having a scanner visible at certain places and events can result in a quick escort out the door! Many avid scanner fans have both a home scanner and a portable unit.

Scanners really differ in the number of channels you can program in them. Some low cost scanners only have a couple of dozen channels available, while some deluxe scanners have 1000 or more channels you can program. The best advice here is to buy a scanner with more channels than you think you will need, as you'll probably run across interesting new frequencies you want to monitor. Maybe the most common wish of scanner fans is that their radios had more channels!

Make sure you understand how new frequencies can be programmed into a scanner. Some scanners will let you enter new frequencies only in specific increments, such as at 5 kHz intervals. Others force you to use the standard spacing between channels commonly used on a given band. More advanced scanners let you enter frequencies down to a single kilohertz. A scanner that tunes only in fixed increments means you may miss hearing some interesting things.

Most scanners automatically tune narrow band (that is, deviation of 5 kHz or less) FM on all frequencies except for the 108 to 136 and 225 to 400 MHz aviation bands, where AM is used. Some scanners allow you to receive wide band FM (deviation of 10 kHz or more) as well. This will let you monitor the FM broadcast band, television audio, and some government transmissions. However, use of wide band FM outside of the FM broadcast band and television channels is rare. A few scanners, such as the Icom R10 let you receive SSB as well, but SSB is seldom used above 30 MHz outside the ham radio bands, and even there narrow band FM heavily dominates. For most listening, a scanner that tunes narrow band FM (and AM on the aviation bands) should be more than adequate.

If you would like to monitor scanner frequencies and AM and shortwave, then consider a wideband receiver. Such radios offer exceptional frequency coverage and models such as the Icom R5 are quite affordable.

 

Understanding Specifications

The importance of the specifications indicating a scanner's performances largely depends on where you live. If you live in a large urban area, you will need a high degree of selectivity (the ability to reject interfering signals) because of the large number of radio signals found in urban areas. If you live in a rural area with few stations, then greater sensitivity (the ability to detect weak radio signals) will be more important.

Sensitivity is measured in microvolts, abbreviated mV. The lower the number of microvolts, the weaker the signal that the scanner can detect and produce intelligible audio from.

Selectivity is measured in kHz for a certain level of interference rejection. This rejection is measured in decibels (dB), usually at 50 dB. A "50 dB" rejection means an interfering signal is reduced to a level 100,000 times weaker than its actual strength. If a scanner has a selectivity specification of "40 kHz at 50 dB," this means signals 40 kHz or more away from the signal you want to hear are reduced in strength 100,000 times.

If you live in a rural area, good sensitivity is more important than good selectivity. With fewer stations to hear, you need to be able to catch weak signals and don't have to worry as much about interference. In an urban area, the opposite is true; your main concern is in rejecting interference from stations on adjacent channels, not catching weak signals. In a rural area, narrow band FM selectivity of 40 kHz at 50 dB will usually be adequate, while in an urban environment you will usually need selectivity of 30 kHz at 50 dB or better.

Signals can also "mix" in a scanner's internal circuits, producing false signals known as images. Images are an unavoidable by-product of a scanner's circuitry, but the better scanners can reject most of these phantom signals and reduce their strength. Image rejection is how this is measured, and a good scanner should have image rejection of 50 dB or greater.

While there are some exceptions, as a general rule you do get what you pay for in scanner performance. More expensive models will have better sensitivity, selectivity, and image rejection than less expensive units.

Some municipalities use trunking systems whereby a group or block of frequencies are used on a rotating basis. To properly copy such transmissions, you will need a Trunk Tracking scanner such as the Bearcat BC245XLT with Trunk Tracking that can "follow" the various channels as they are used and changed.

Some municipalities are now transmitting in APCO25 digital voice mode. Traditional scanners cannot "decode" these voice transmissions. Some of the newer scanners such as the Bearcat BC296D can handle both Trunk Tracking and Digital transmissions.

 

Scanner Features and Controls

Here are explanations for features and controls commonly found on scanners:

  • Attenuator. This reduces the sensitivity of a scanner in order to reduce images and other effects of strong nearby signals.
  • Audio squelch. This resumes scanning if a signal has no audio on a channel after pausing on the channel for a few seconds.
  • Autoload. This automatically stores new frequencies found during a search into the scanner's memories.
  • Bank. This is a way of dividing a scanner's channels into smaller, manageable blocks for specific purposes.
  • Delay. This determines how long a scanner pauses on a channel for another transmission before resuming scanning.
  • Hold. This lets you stop scanning on a channel so you can monitor it continuously.
  • Lockout. This causes the scanner to skip over a channel during its scanning sequence.
  • Priority channel. When a signal is present on a priority channel, the scanner switches to it regardless of whether signals are present on other channels being scanned.
  • Search. With this, the scanner tunes through a range and stops when an active frequency is found. This is very handy for finding new stations and users not listed in frequency directories.
  • Squelch. This silences the scanner's audio until a signal of a certain strength is received. The squelch level can be manually set.


Universal Radio offers a good selection of scanners and wideband radios.


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