Campbell Scientific RF300-Series DRL VHF/UHF Radio Transceivers - Manual (Page 51)

G-1
APPENDIX G. P50 RADIO
G.1 P50 RADIO SETUP AND
SPECIFICATIONS
The P50 Radio transmits and receives data
blocks. The volume, squelch, and frequency
controls on the radio must be set properly.
G.1.1 VOLUME CONTROL
The volume control should be set to
approximately 1/2 of the operational range.
This is equivalent to approximately 9:00
assuming the off position is at 4:00. Marginal
RF links can be enhanced by "fine tuning" the
volume control at any respective RF station.
G.1.2 SQUELCH CONTROL
The squelch control determines the input power
level that the radio will break squelch. The
squelch control should be set fully clockwise or
approximately 12:30.
G.1.3 FREQUENCY SWITCH
The frequency switch should always be set to 1,
unless you are using a dual frequency system.
G.1.4 P50 SPECIFICATIONS
VHF UHF
Power output 5W 4W
Frequency (MHz) 150-174 450-470
Channel capability 2 2
Dimensions 6.7"x2.5"x1.2" 6.7"x2.5"x1.2"
Weight 15.5 oz 15.5 oz
FCC Designation AZ489FT3729 AZ489FT4724
Current drain
Quiescent
10 mA 1.35 A
Active 15 mA 1.10 A
FIGURE G-1. P50 Radio Settings
G.2 ADDITIONAL TROUBLESHOOTING
FOR P50 RADIO
To test a station's radio/cable/antenna
transmission capabilities, a directional
wattmeter is needed such as Bird Electronic
Corporation's Model 4304A Wattmeter. Proper
connectors are also needed to place the
wattmeter in series between the radio and
antenna cable. A voltmeter is required to
measure the battery voltage of the datalogger
with and without radio transmission.
Place the wattmeter in series between the radio
and antenna cable. Set the wattmeter to the 15
Watt range, or the next highest wattmeter
setting, and point the directional arrow first
toward the antenna cable to measure forward
power (Wf). Depress the transmit button on the
radio, let the wattmeter stabilize, and write down
the wattmeter reading. Reverse the directional
arrow so it is pointing back toward the radio,
depress the transmit button, let the wattmeter
stabilize, and write down the wattmeter reading.
This second reading is the reflected power
(Wr). Take the square root of the quantity
reflected power divided by the forward power to
arrive at the square root ratio (R). Calculate the
Voltage Standing Wave Ratio (VSWR) with the
following equation:
VSWR = [(1+R) / (1-R)]
where, R = (Wr / Wf)
1/2
.
The impedance of the R transmission cable
(usually RG-8A/U) and antenna combination
should match the impedance (50 ohms) of the
radio output circuit. When the transmission
cable or antenna does not match the
impedance of the output circuit of the radio, not
all of the energy supplied to the cable will flow
into the antenna. Some of the energy supplied
will be reflected back to the radio, causing
standing waves on the cable. The ratio of
voltage across the line at the high voltage points
to that at the low voltage points is known as the
Voltage Standing Wave Ratio, or VSWR. The
VSWR should be kept below 1.5:1 for error-free
radiotelemetry.
For example, if the forward power (Wf) is 5
Watts and the reflected power (Wr) is 0.2
Watts, the VSWR is 1.5:1.