Realistic PRO-50 - Images

One very useful service is the National Weather Service’s
continuous weather broadcast. 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 - 162.400, 162.425,
162.450, 162.475, 162.500, 162.525, or 162.550 MHz. In
most areas of the country, you can receive at least one of
these frequencies.
Frequencies in different bands are accessible only at spe¬
cific intervals. In the VHF-Lo, HAM, Government, and VHF-
Hi bands, frequencies are available in 5 kHz steps. In all
other bands, 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.
IMAGES
You might discover one of your regular stations on a fre¬
quency that is not listed. This could be what is known as an
image. For example, if you suddenly find you hear the same
broadcasts on 453.5750 as you hear on 474.9750, do a little
math to see if it is an image. Take this unit’s intermediate fre¬
quency of 10.7 MHz and double it. Then, subtract it from the
new frequency. If the answer is the regular frequency, you
have tuned to an image. Occasionally, you might get inter¬
ference on a weak or distant channel from a strong broad¬
cast 21.4 MHz (10.7 MHz x 2) below or above the tuned
frequency. This is rare, and the image signal is usually
cleared whenever a broadcast on the actual frequency is in
progress.