User's Manual

46 MDS Mercury 16E Technical Manual MDS 05-6302A01, Rev. A
Transmitter Power Output and Antenna System SWR
Introduction A proper impedance match between the transceiver and the antenna
system is important. It ensures the maximum signal transfer between the
radio and antenna. The impedance match can be checked indirectly by
measuring the SWR (Standing Wave Ratio) of the antenna system. If the
results are normal, record them for comparison for use during future
routine preventative maintenance. Abnormal readings indicate a pos-
sible trouble with the antenna or the transmission line that will need to
be corrected.
The SWR of the antenna system should be checked before the radio is
put into regular service. For accurate readings, a wattmeter suited to the
frequency of operation is required. One example of such a unit is the
Bird Model 43
™
directional wattmeter with an appropriate element
installed.
The reflected power should be less than 10% of the forward power
(2:1 SWR). Higher readings usually indicate problems with the
antenna, feedline or coaxial connectors. If the reflected power is more
than 10%, check these areas for damage.
Procedure 1. Place a directional wattmeter between the radio (TX/RX connector)
and the antenna system.
2. With the transmitter keyed, measure the forward and reflected
power on the wattmeter. Reflected power should be no more than
10% of the forward power. Record these readings for future refer-
ence.
NOTE: The transmitter has a 10-minute ti mer. When in test mo de, it
will dekey after 10 minutes of continuous operation. The
Radio can also be dekeyed by temporarily disconnecting the
radio’s DC power.
3. Dekey the transmitter and disconnect the wattmeter. Reconnect the
antenna feedline to the radio.
End of procedure
Antenna Heading Optimization
Introduction The radio network integrity depends, in a large part, on stable radio
signal levels being received at each end of a data link. In general, signals
stronger than –80 dBm provide reliable communication that includes a
fade margin for signal variances. As the distance between the Base Sta-
tion and Subscriber Unit increases, the influence of terrain, foliage and
man-made obstructions become more influential and the use of direc-
tional antennas at Remote locations becomes necessary. Directional
antennas usually require some fine-tuning of their bearing to optimize