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(200-0402)        A General Guide to Scanning         Faxback Doc. # 18550

BIRDIES

Birdies are the products of internally generated signals that make some
frequencies difficult to receive.  If you program one of these frequencies,
you hear only noise on the channel.

If the interference is not severe, you might be able to turn SQUELCH
clockwise to cut out the interference.  The most common birdies to watch
for are listed below.

Birdie Frequencies:

 31.545 MHz          164.835 MHz
 38.400              165.040
 51.200              167.855
120.600              168.855
122.700              171.855
135.200              383.475
140.890              399.250
143.910              418.125
144.910              419.100
147.660              429.650
through              431.9875
147.700              435.775
152.880              439.800
160.815              440.525
163.830              444.550

RECEPTION NOTES

Reception on the frequencies covered on your scanner is mainly line-of-
sight.  That means you usually won't be able to hear stations at your
listening horizon that are located beyond the horizon.

During summer months, you might be able to hear stations in the 30-50 MHz
range located several hundreds or even thousands of miles away.  This type
of reception is unpredictable, but often very interesting.

One very useful service is the National Oceanic Atmospheric Administration
(NOAA) Weather Radio's continuous weather broadcasts.  These broadcasts
contain weather forecasts and data for the area around the station, 
plus bulletins on any threatening weather conditions.  These stations
use seven frequencies (between 162.40 and 162.55 MHz).  In most areas of
the country, you can receive one or more of these frequencies.

A GUIDE TO THE ACTION BANDS

With a little investigation, you can find active frequencies in your
community to monitor exciting events.  We can give you some general
pointers on finding those frequencies, and you can take it from there.
Please use caution and common sense when you hear an emergency call.
Never go to the scene of an emergency.  It could be very dangerous.

Find out if there is a local club that monitors your community's
frequencies.  Perhaps a local electronics repair shop that works on
equipment similar to your scanner can give you channel frequencies used by
local radio services.  A volunteer police or fire employee can also be a
good source for this information.

As a general rule on VHF, most activity concentrates between 153.785 and
155.98 MHz and then again from 158.73 to 159.46 MHz.  Here you find local
government, police, fire, and most emergency services.  If you are near a
railroad or major railroad tracks, look around 160.0 to 161.9 for signals.

You can hear commercial aircraft transmissions between 118 and 136.975
MHz.  Military aircraft operate between 225 and 400 MHz.

In some large cities, the UHF bands are used for emergency services.  Here,
most of the activity is between 453.025 and 453.95 MHz and between 456.025
and 467.925 MHz.

In the UHF band, frequencies between 456.025 and 459.95 MHz and between
465.025 and 460.975 MHz are used for mobile units and control stations
associated with base and repeater units that operate 5 MHz lower (that
is, between 451,025 and 454.95 MHz and between 460.025 and 464.975 MHz).
This means that if you find an active frequency inside one of these 
spreads, you can look 5 MHz lower (or higher) to find the base station
repeater for that service.

A newer technology is now available that uses the 800 MHz band for many
services.  Trunked radio, introduced to business systems in 1975, is now
used by public safety agencies.  With up to twenty channels available, the
transmitter automatically selects an unused frequency each time it is
activated.  Several agencies can share such a system without interfering
with each other.  This system can provide secure communications for
selected units, with unselected units unable to hear the messages.

Frequencies in different bands are accessible only at specific intervals.
In the VHF-Lo, HAM, Government, and VHF-Hi bands, frequencies are available
in 5 kHz steps.  In the aircraft band, frequencies are available in 12.5
kHz steps.  Your scanner rounds the entered frequency down to the nearest
valid frequency.   For example, if you try to enter 151.473, the scanner
accepts this as 151.470 MHz.


(12/27/95)