Marti RPT-30, Руководство пользователя

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ANTENNAS
BASE STATION ANTENNA IN-
STALLATION CHECKLIST
The following suggestions are offered to help
those responsible for antenna installations avoid costly
errors in assembly and adjustment. Marti Electron-
ics, Inc. assumes no responsibility for the installation
and performance of antenna systems associated with
its equipment. The following suggestions are not
intended to be a complete step-by-step procedure,
simply a listing of some of the most frequently re-
ported errors in antenna system installation.
Antenna Assembly
Follow the manufacturer's instructions carefully. If
no instructions were included with the antenna, call or
write the antenna manufacturer for instructions. Anten-
nas which have phasing or stacking cables must be as-
sembled carefully to avoid phase reversal or signal can-
cellation.
Transmission Line Connector Assembly
Do not use RG-58 U or RG-8 U cable for STL
station antennas! They have too much loss at VHF and
UHF frequencies. Follow the instructions furnished by
the manufacturer when cutting coaxial cable. Inspect the
cable ends for small metal fragments which can short-
circuit the line inside the connector assembly. Check the
line for a short-circuit condition after each connector is
installed by using an ohmmeter. Pressurized line should
be checked for several days under pressure before instal-
lation on a tower to ensure that there are no leaks in the
line or fittings
Moisture Proofing Coax Connectors and
Fittings
Extreme care must be exercised with coaxial cable
before and after connectors have been installed to ensure
that moisture does not enter the line. Foam dielectric line
can take on moisture absorption which is difficult to
detect and remedy. Therefore, keep the line dry while in
storage with ends tightly capped. Coaxial splices, connec-
tors, and fittings, to be located outside should be made
mechanically tight, then coated with a weather-proofing
material over at least two layers of vinyl plastic electrical
tape. Moisture problems in antenna systems are usually
traced back to connectors which have NOT been properly
taped. The Marti K-1 Grounding and Weatherproofing
Kit is recommended for use in each new antenna
installation.
Location and Grounding of Coaxial Ca-
ble
Keep the RPU receiver coaxial cable as far from the
broadcast transmitter and its coaxial cable as possible.
DO NOT STRAP RECEIVER CABLE TO THE MAIN
ANTENNA CABLE AT ANY POINT. PLACE THE
RECEIVER ANTENNA COAXIAL CABLE ON THE
OPPOSITE SIDE OF THE TOWER FROM THE
MAIN ANTENNA CABLE
. Maintain maximum separa-
tion between these cables at all points, including the dis-
tance from tower base to transmitter building as well as
inside the building.
System Grounding
It is essential that the RPU antenna system be
properly grounded for safety and proper operation.
Antenna Installation and Adjustment
The polarization of the transmit and receive antennas
of the RPU system must be the same! This means that if
the transmitting antenna is vertical, the receiving antenna
must also be vertical. Each antenna should be attached to
the tower using the proper side mount or top mount
hardware. If an RF wattmeter is available, each antenna
and transmission line can be checked for VSWR when the
transmitter is supplying power to it. The VSWR should
be less than 1.5 to 1 (1.5:1).
IF THE ANTENNA
SYSTEM FAILS TO GIVE THE PREDICTED
SIGNAL STRENGTH LEVEL, THE FOLLOWING
ITEMS SHOULD BE CHECKED:
1. Check for correct assembly of antenna.
2. Check that antennas have same polarity.
3. Check VSWR of both transmit and receive antennas.
VSWR should be less that 1.5:1.
4. Check for obstructions in the path such as trees and
man-made structures. The base antenna must be high
enough to provide a line-of-sight path to the remote
transmitting
antenna.
CAUTION & WARNING
Y
OU CAN BE KILLED IF AN ANTENNA COMES IN
CONTACT WITH ELECTRIC POWER LINES OR
EXPOSED ELECTRICAL WIRING
. F
OR YOUR
SAFETY USE EXTREME CAUTION WHEN IN
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