12
MDS 1710A/C and MDS 2710A/C/D
MDS 05-3447A01, Rev. F
Invisible place holder
Figure 7. Typical Yagi Antenna (mounted to mast)
Feedlines
The selection of antenna feedline is very important. Poor quality cables
should be avoided as they will result in power losses that may reduce the
range and reliability of the radio system.
Table 3
shows the losses that will occur when using various lengths and
types of cable at 200 MHz. Losses at 130-174 MHz will be slightly
lower. Regardless of the type of cable used, it should be kept as short as
possible to minimize signal loss
† Cable loss slightly lower at 130-174 MHz.
3.4 Power Connection
The transceiver can be operated from any well-filtered 10.5 to 16 Vdc
power source. The power supply should be capable of providing at least
2.5 amperes of continuous current.
The red wire on the power cable is the positive lead; the black is nega-
tive.
NOTE:
The radio is designed for use only in negative ground systems.
Table 3. Length vs. Loss in Coaxial Cables at 200 MHz
†
Cable Type
3 Meters
(10 Feet)
15 Meters
(46 Feet)
30 Meters
(91 Feet)
150 Meters
(525 Feet)
RG-8A/U
0.32 dB
1.6 dB
3.2 dB
16 dB
1/2 inch HELIAX
0.10 dB
0.49 dB
0.98 dB
4.9 dB
7/8 inch HELIAX
0.05 dB
0.27 dB
0.54 dB
2.7 dB
1-1/4 inch HELIAX
0.04 dB
0.20 dB
0.40 dB
2.0 dB
1-5/8 inch HELIAX
0.03 dB
0.17 dB
0.33 dB
1.65 dB
MDS 05-3447A01, Rev. F
MDS 1710A/C and MDS 2710A/C/D
29
SHOW [DC, PORT, PWR]
The
SHOW
command displays different types of information based on
the command variables. The different parameters are:
•
DC
—Display DC input/output voltages
•
PORT
—Display the connector port (RJ-11 or DB-25) that is active
for diagnostics and control.
•
PWR
—Display RF power output
SNR
This command continuously displays the signal-to-noise ratio of the
received signal expressed in dB, until you press the Enter key. As used
in this guide, the signal-to-noise measurement is based upon the signal
level following equalization, for received frames.
The SNR is an indication of the received signal quality. The SNR indi-
cation ranges from 10 dB to 33 dB. A value of 10 dB represents a very
poor signal. A value of 24 dB represents a very good signal.
When the SNR command is used, it causes the
DIAG.
port to enter an
update mode, and the signal-to-noise ratio is updated and redisplayed
every 2 seconds. The SNR continuously updates until the
key is
pressed.
SREV
This command displays the software revision level of the transceiver
firmware.
STAT
This command displays the current alarm status of the transceiver.
If no alarms exist, the message
NO ALARMS PRESENT
appears at the top
of the HHT display.
If an alarm does exist, a two-digit code (00–31) is displayed and the
alarm is identified as “Major” or “Minor.” A brief description of the
alarm code is also given.
If more than one alarm exists, the word
MORE
appears at the bottom of
the screen and additional alarms are viewed by pressing the
key. Detailed descriptions of event codes are provided in
Table 8 on
page 32
.
TEMP
This command displays the internal temperature of the transceiver in
degrees Celsius.
ENTER
ENTER
