What Is A Scanner?
-
A scanner/receiver is much like the radio in your car. It is able to tune to a
selected frequency and then extracts the audio portion of the signal which gets
fed to an amplifier and then sent to a speaker for you to hear.
-
If you have a modern radio in your car, it probably has a number of station
presets. And you've probably programmed each preset with a favorite radio
station. Then when you press a particular preset button, the radio tunes to the
appropriate frequency.
-
Many radios have more than one set of presets too. Something like FM1 and FM2
etc. Pressing FM1 enables the presets that were programmed for it and FM2
contains a whole other set. So if you have 6 presets for both FM1 and FM2, you
have twelve frequencies you can program.
-
Let's say, instead of calling them presets, we call them "channels". And let's
refer to FM1 and FM2 as "banks". Your car radio then has two banks with six
channels each, right? You can now think of your car radio in terms of a
scanner! Most scanners come with anywhere from 5 to 20 banks with anywhere from
10 to 50 channels per bank. Since each channel can be programmed to hold a
discrete frequency, an average scanner can be programmed with 50 to 1000
frequencies! That may seem like a lot, but remember, the range of radio
frequencies that are out there is HUGE!
A Scanner Therefore Scans
-
Unlike broadcast radio and TV which transmit pretty much 24 hours a day,
services such as police and fire only transmit when a person presses the
transmit key on the microphone. If there is no transmission, there is only
static on that frequency. This is where scanning comes in.
-
When you tell the scanner to start scanning, it examines each of the
frequencies you have programmed it. It looks at the first frequency and checks
to see if someone is transmitting on it. If there is no transmission detected,
it simply moves on to the next channel to check it.
-
If there is a transmission, it pauses the scan operation, extracts the audio,
amplifies it and sends it to the speaker for you to hear.
-
When the transmissions stops, the receiver continues on to the next channel.
When it reaches the last channel, it starts over at the first channel and
repeats the process.
A Scanner Can Search To?
-
Have you ever been in a strange area and used the "tune" function of your radio
to search for a station? This is called searching and most good scanners can do
this.
-
If your scanner has a limit search, you can tell it to search for active
frequencies between two specified frequencies. You usually specify a start
frequency and an end frequency and tell the scanner to search between these two
frequencies.
-
The scanner starts at the first frequency and checks for a transmission. If
there is none, it goes to the next frequency and repeats the process. Just like
scanning, if a transmission is found, you get to hear what is being broadcast
on it.
-
If your scanner has band search, you select the band (consisting of a
pre-programmed start and end frequency) you want to search and off it goes.
While not as flexible as a limit search, it still gives you the ability to
search for new frequencies.
-
If your scanner has service search, this is really just a scan operation which
searches for activity among a set of pre-programmed frequencies. They are
usually kept in a separate memory and can not be altered.
So Now You Know
-
There you have it. A scanner is a radio receiver that has the ability to scan
pre-programmed channels that you know of, as well as the ability to search for
new ones. Just like your car radio! Just think of it as a specialized scanner
that can receive a small portion of the radio spectrum.
So What's A Communications Receiver
-
This is really nothing more than a fancy name for a scanner.
-
However, a communications receivers usually has at least one VFO linked to a
rotary control and allows the frequency step size and receive mode to be
altered (see the Glossary page for the definitions of
these terms)
-
Communications receivers usually scan and search a lot slower than a
"pure-bred" scanner.
-
To make a broad generalization, Alinco, AOR, Icom, WiNRADiO, Yaesu and Yupiteru
make models that would be termed communications receivers while Radio Shack and
Uniden make scanners.
-
There are even some radios that call themselves multi-band receivers. Same
difference.
|
