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| Picking A Scanner |
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Home Contents |
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Getting Up To Speed
First, let's take a look at all of the
services
that use radios to get their jobs done.
We'll now need to define what a scanner is and what it does.
Lastly, you'll need to read this glossary to get a grip on the lingo used.
Major Considerations
Price
Like most things in life, you get what you pay for. Don't expect the
performance of an expensive Ferarri if you buy a "cheap" domestic.
Basic price ranges :
Save money by buying used but make sure it's in good shape. And you must consider the risk involved if the purchase is not going to be made face-to-face. If it's an older model (8+ years), consider the possibility that when it breaks, there is a HIGH likelihood that you will be unable to find the personnel or parts needed to repair it!
It's useful to buy from RadioShack (nationwide chain) a model which you are interested in and is hopefully on sale. You'll get 30 days to test drive it which can be invaluable for the beginner to put the knowledge on this page to use. If you don't like it, take it back. You may decide that scanning isn't for you, or it may help you decide the next radio you should try.
Types
The wider the frequency range of a reciever, the more it is going to cost.
The basic agencies covered by the "average" receiver:
The above coverage generally results in reception of the following bands: 30-54 (60-88 in the UK), 118-174, 400-512 & 806-960 MHz.
Such segmented or non-continuous frequency coverage is found on most models made by Commtel, GRE, RadioShack, RCA, Realistic, RELM, and Uniden
Agencies which may require additional frequency coverage:
To cover all these agencies and more, you'll need to look into buying a more expensive, wide frequency (continuous) model made by Alinco, AOR, Camnis, Icom, Stabo, Standard, Trident, Welz, WiNRADiO, Yaesu or Yupiteru
There are also models with continuous frequency coverage of VHF/UHF but do not cover HF available from Optoelectronics and Sony.
Trunked Radio Systems
With more and more agencies going to trunked radio systems (multi-channel,
computer-controlled) for more efficient use of their bandwidth, it's worth the
effort to see if you would benefit from buying a scanner which can track
transmissions on one of these "high tech" systems.
Trunked radio systems are usually used by public safety and businesses in and around urban areas where the number of users is large and the cost can be paid by local government taxes or expensive leasing fees. Therefor, if you live in or near a large urban area, check into whether or not there are trunked systems you wish to monitor. If you live in the "sticks", this type of radio PROBABLY won't be a consideration.
If you do find there are one or more trunked radio systems you wish to scan, then you'll have to determine if these systems can be tracked by the current set of scanners. Not all trunked systems are the same!
The two predominant trunked types are Motorola and GE/Ericsson with Motorola being the more popular. You must also consider whether the signals they carry are analog or digital. There are NO scanners which can handle digital trunked systems. If that's the type of system you have, sorry, but too bad.
While most trunked systems are on 800 MHz, they can also be found in the 100, 400, 500, and 900 MHz ranges! Be sure to investigate what your needs are, then make sure you pick the radio which can handle trunked systems in these frequency ranges. Not all scanners are created equal!
Off the shelf trunked system scanning radios can be purchased from Optoelectronics (OptoCom), RadioShack (PRO-2050, PRO0-2052, PRO-2066, PRO-90, PRO-91, PRO-92, PRO-94 & PRO-2067) and Uniden (BC235XLT, BC895XLT, BC245XLT)
Other Considerations
Conversion
What to buy? Double or Triple circuitry design?
This category refers to the number of receive stages built designed into the radio's superheterodyne circuitry
Double is usually more sensitive but is prone to images and being overloaded by strong signals in an urban locale. This means more interference annoyances while trying to monitor
Triple is used to help eliminate images which can be annoying until you learn to spot them. And such filtering is usually indicative of a more 'costly' receiver design which usually does a better job of blocking other forms of interference as well
Triple is obviously more expensive
Recent legislation passed in the US basically puts an end to double conversion models to prevent listening to cellular telephone images. So all new models are coming out with triple conversion while popular, older double conversion models are being retrofitted over to use triple. This change may very well have a ripple effect over into the European and Asian markets as well
Sensitivity
Double-edged sword; if a radio is too sensitive, it may be overwhelmed by
strong signals creating intermod or possibly even reduce sensitivity due to
desensitization
In rural locales, chances for very strong signals are unlikely. You should be more interested in trying to pick up weak signals from far away so the more sensitivity, the better
In urban/suburban locales, there are many more strong signals so too much sensitivity will be a hindrance. You will want a good mix between sensitivity and good filtering (interference rejection)
Dense, urban areas are not very conducive to long distance or weak signal reception. For typical local monitoring, signal strengths are very strong so sensitivity is not really a factor; better filtering is
Sensitivity figures are usually listed in microvolts. The lower the number quoted, the higher its sensitivity. Todays models have figures for the following receive modes: FM=0.3-0.5µV, AM=0.8-1.0µV and WFM=1.5-2.0µV
Number Of Channels
Depends on where you live and how many agencies you will listen to
Today's models range from 16 to 54,000 channels!
If you can hook it up to your computer, the number of channels is usually only limited by hard disk space
The average today is about 200 channels
Bare minimum to get is probably 100 channels (rural). Shoot for 200 if you live in or around a decent-sized city. If you live in a large metropolitan area, you better plan ahead because you'll be surprised at how quickly the channels get filled up!
Number Of Banks
For logical grouping and organization, each agency you listen to is usually
placed in a separate bank
The more banks you have, the easier it is to segregate your agencies making your monitoring sessions more efficient and therefore more productive
Today's models range from 1 to 234 banks
Again, if you hook up to a computer, you don't have to worry about running out of them
Today's average is about 10-20 banks which is a good number
Number Of Channels Per Bank
A very important consideration since each bank is typically used to store a
single agency
Consider the maximum number of frequencies used by any one of the agencies you wish to monitor. If they are simple radio systems which use just a few channels, almost any scanner will do. For larger or trunked systems, you may need 20, 30 or more channels to hold all the frequencies for that agency
Keep in mind that more than one bank can be used to hold a single agency. Just makes channel usage and operation a little less efficient
One reason to consider channels/bank is due to possible inefficient memory usage. If the agencies you listen to only use 4 or 5 frequencies and you put each in a separate bank, it is very inefficient in terms of "wasted" channels if your radio has 100 channels/bank!
Today's models range from 10 - 100 channels/bank
Today's models average around 20 - 30 channels/bank
Scan/Search Speed
Today's models can scan from 6 to 100 channels/second and can search from 15 to
300 frequencies/second
The average for scanning is around 50 channels/second and for searching is around 100 channels/second
Keep in mind that these figures are manufacturers theoretical limits. If you have banks with frequencies which are not in numerical order and/or have frequencies in the lo-VHF, hi-VHF, UHF and 800MHz ranges, these will slow down operation
While a high scan/search rate may seem one of the more important factors in your decision, it takes a back seat to many others in many cases
A scan rate of 25 - 50 channels/second is fine for most individuals when you consider the number of frequencies that are listened to at any one time
A search rate of 50 frequencies/second is fine for most people
Receive Modes
Cheapest models have just FM which is used for most agencies in the VHF/UHF
spectrum (30 - 3000 MHz)
Next level includes AM for aircraft bands (commercial & military). If your receiver has HF coverage (3-30 MHz), AM is used on most signals in this range
Next level includes wide FM (WFM) for FM broadcast (88-108 MHz) and TV audio (54-72, 76-88, 174-216 & 512-806)
Next level includes single sideband (SSB) (HF) and amateur radio signals (HF/VHF/UHF))
Some exotic models might have CW (continuous wave = Morse Code) and variations on narrower and wider AM/FM bandwidths to accomodate more types of signal bandwidths
Cheapest models have fixed modes for each frequency meaning that once a frequency is entered, the radio automatically selects the receive mode and you can't override it
More expensive units allow the user to select or override the receive mode which is the most flexible approach
Step Sizes
Cheapest models have just 5 & 12.5 kHz which works for most channel spacings
on VHF & UHF (which use 5, 10, 12.5, 15, 20, & 25 kHz separation)
The next level includes 25 kHz for aircraft bands and 800 MHz
The next level includes 50/100 kHz for wide FM (WFM)
The next level is usually a big jump including 1, 6.25, 10, 15, 20, & 30 kHz step sizes which are useful on HF, VHF and UHF
Most exotic models may have 1, 10, 50 & 100 Hz (used on shortwave) and 9, 150, 200 kHz (VHF/UHF signals) and sometimes even user-defined step sizes
All of these step sizes are also designed to cater to the different frequency spacings found in North America, Europe and Asia
Cheapest models have fixed step sizes for frequency ranges meaning that the step size is based on the frequency being tuned and can't be overridden
More expensive units allow the user to select or override the step size which is the most flexible approach
Search Types
Audio
Power is a consideration especially for handhelds. If the radio is overwhelmed
in noisy surroundings, an earphone/headphones may be needed. In a vehicle, most
handhelds will benefit from the use of a dedicated amplified speaker, or
special cassette adaptor allowing the audio to be fed into and thereby
amplified by your car stereo
Quality of the audio simply adds more enjoyment to your monitoring sessions. Especially if you listen to wide-FM signals such as FM broadcast or TV audio. Even for mundane police and fire, crisp and rich sounding FM signals are more pleasurable than a radio with "mushy" audio
Don't ever trust manufacturer specs for audio power or use these figures to compare models. I know of some radios spec'd at 100 milliwatts (mW) that are louder than some spec'd at 250 mW
Power
| Copyright © 2004 by Richard J. Wells |
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