PRO-2039 Scanner  (200-0462)    Frequency Conversion   Faxback Doc. # 15929

AVOIDING IMAGE FREQUENCIES

You might discover one of the regular stations on another frequency that
is not listed.  It might be what is known as an image frequency.

For example, you might find a service that regularly uses a frequency of
453.275 also on 474.675.

To see if it is an image, do a little math.

Note the new frequency                                      474.765
Double the intermediate frequency of 10.7 MHz (21.400)
and subtract it from the new frequency.                     -21.400
                                                           ─────────
If the answer is the regular frequency,                     453.275
then you have tuned to an image.

Occasionally you might get interference on a weak or distant channel from
a strong broadcast 21.4 MHz below the tuned frequency.  This is rare, and
the image signal is usually cleared whenever there is a broadcast on the
actual frequency.

FREQUENCY CONVERSION

The tuning location of a station can be expressed in frequency (kHz or
MHz) or in wavelength (meters).  The following information can help you
make the necessary conversions.

1 MHz (million) = 1,000 kHz (thousand)

To convert MHz to kHz, multiply by 1,000:

   30.62 MHz x 1000 = 30,620 kHz

To convert from kHz to MHz, divide by 1,000:

   127800 kHz
  ────────────  = 127.8 MHz
      1000

To convert MHz to meters, divide 300 by the number of megahertz.

   300
  ─────   = 1.75 meter
 171 MHz


(TE/all-07/18/95)