Marti Electronics STL-10A, Technical Manual

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7
Location and Grounding of Coaxial Cable.
Keep the STL receiver coaxial cable as far from the broadcast transmitter and 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 separation between these cables at all points, including the distance from tower base to
transmitter building as well as inside the building.
System Grounding.
It is essential that the STL antenna system be properly grounded for safety and proper operation. Ensure the antenna
system is properly grounded.
Antenna Installation and Adjustment.
The polarization of the transmit and receive antennas of the STL system must be the same. This means that if the
transmitting antenna is horizontal, the receiving antenna must also be horizontal. Each antenna should be attached to
the tower to allow for final adjustment in azimuth heading and vertical tilt.
After visual adjustment of the antennas, the transmitter and receiver can be used to make the final adjustments of the
antennas. With the transmitter driving one antenna, the receiving antenna is adjusted for maximum signal (indicated
on the receiver) in both horizontal and vertical directivity. CAUTION: Antennas have a “major” and several
“minor” lobes in their directivity patterns. A common error is to peak the antenna on a minor lobe, resulting in a
signal level of only a fraction of the major lobe signal. This error can be avoided only by swinging the antenna
through a large angle so that all lobes are evaluated and the major lobe clearly determined. After one antenna is ad-
justed, the transmitter and receiver locations are reversed, to allow adjustment of the other antenna. If an RF watt-
meter 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, check the following items:
1. Check for correct assembly of antenna.
2. Ensure the antennas have same polarity.
3. Check orientation of antennas in both horizontal and vertical directions.
4. Check VSWR of both the transmit and receive antennas. VSWR should be less than 1.5:1.
5. Check for required Fresnel zone path clearance at all points along radio path.
6. Check for obstructions in the path such as trees and man–made structures. Do not depend on maps or aerial
photographs.
WARNING
WARNING
YOU CAN BE KILLED IF AN ANTENNA COMES IN CONTACT
WITH ELECTRIC POWER LINES OR EXPOSED ELECTRICAL
WIRING. FOR YOUR SAFETY USE EXTREME CAUTION WHEN
INSTALLING ANTENNAS. KEEP AWAY FROM POWER LINES.
OPERATION.
SWITCH AND METER FUNCTIONS.
TRANSMIT–OFF Switch & LED.
This toggle switch controls the RF output of the transmitter. The red LED above this switch is a visual indication
that the switch is in “TRANSMIT” position. The audio circuits, the 13.5 volt regulated power supply and the meter
illumination lamps remain on when the TRANSMIT switch is “OFF”.