Preventive Maintenance; Visual Inspection; Periodic Cleaning - Motorola CDR500 Programming Manual

Introduction to Repeaters and Components

Preventive Maintenance

the transmit radio with separate transmission lines. The
separation necessary to yield the desired 70 dB of isola-
tion is dependent upon the frequency band of operation.
It is obvious from the following charts that, for all verti-
cally polarized antennas in use for land mobile services,
vertical spacing will get the 70 dB more easily than hor-
izontal spacing. The horizontal spacing may be reduced
if buildings, hills, or mountains are present between the
antennas; the amount of reduction has to be determined
by experiment. Table 1-7 shows the vertical spacing and
Table 1-8 shows the horizontal spacing,.
NOTE
The losses associated with long transmis-
sion lines have not been included in the
calculations of the spacings. It is readily
apparent that horizontal spacing of
antennas is somewhat useless; the cost of
the transmission lines to the two anten-
nas would be greater than the cost of a
duplexer.
NOTE
The two antennas will couple to a com-
mon metallic support; the position of one
of the antennas may have to be varied to
attain the desired isolation.
NOTE
The following tables contain spacing
information for vertically polarized
antennas used in land mobile services.
Table 1-7. Vertical Spacing
Frequency
(MHz)
30
40
50
150
170
400
470
1-6
Spacing
feet meters
295 90
220 68
177 54
59 18
52 16
22 7
20 6
Table 1-8. Horizontal Spacing
Frequency
(MHz)
30
150
400
Preventive Maintenance
Preventive maintenance of the CDR500 and CDR700
repeaters consist of:

• visual inspection

• periodic cleaning

Visual Inspection
Check that external surfaces of the equipment are
clean, that connecting cables are not damaged, and that
connections are firm. A detailed inspection of the inte-
rior electronic circuitry is not needed or desired.
Periodic Cleaning
Periodically clean smudges and grime from the exte-
rior housing. Use a soft, non-abrasive cloth moistened
in a mild soap and water solution. Rinse the surface
using a second cloth moistened in clean water, and
clean any dirt or debris from the fan grill.
6864110R66-O
CDR500 & CDR700 Repeater Service Manual
Spacing
feet
12,800
2,600
960
meters
3,900
780
293
March, 2001