All Weather Inc 20981 User manual

All Weather Inc. • 1065 National Drive • Sacramento, CA 95834 • USA • 800.824.5873 • www.allweatherinc.com
Model20981
UHFDataRadio
User’s
Manual
Rev. A

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Model 20981 UHF Data Radio User’s Manual
Revision History
Revision
Date
Summary of Changes
A
2020 Feb 15
Initial release.

Model 20981 UHF Data Radio User’s Manual
TABLE OF CONTENTS
OVERVIEW.........................................................................................................................1
1.1 Installation Kits...........................................................................................................................1
1.2 FCC Regulations.........................................................................................................................1
1.2.1 Licensing.............................................................................................................................1
1.2.2 Equipment Authorization (Certification)............................................................................1
1.2.3 Radio Frequency Exposure.................................................................................................2
I/O CONNECTOR AND LED INDICATORS........................................................................3
2.1 I/O Connector .............................................................................................................................3
2.1.1 Pinout Description ..............................................................................................................3
2.2 LED indicators............................................................................................................................5
OPERATION.......................................................................................................................6
3.1 Channel Selection.......................................................................................................................6
3.2 Power Supply Voltage................................................................................................................6
3.3 Current Drain vs Supply Voltage ...............................................................................................6
3.4 Duty Cycle/Key-Down Limitations............................................................................................7
INSTALLATION...................................................................................................................8
PROGRAMMING THE DATA RADIO .................................................................................9
5.1 Frequency Tab..........................................................................................................................10
5.2 Other Tabs ................................................................................................................................10
5.2.1 Buttons..............................................................................................................................10
5.2.2 General Tab.......................................................................................................................11
5.2.3 Modem Page .....................................................................................................................12
5.3 Analog Tab ...............................................................................................................................14
5.4 Summary Tab............................................................................................................................15
5.5 Restore EE Tab.........................................................................................................................15
AWOS INSTALLATION.....................................................................................................17
6.1 DCP Installation........................................................................................................................17
6.2 CDP Installation........................................................................................................................17
MAINTENANCE................................................................................................................18
7.1 AWOS Maintenance Procedures..............................................................................................18
7.1.1 Monthly Maintenance.......................................................................................................18
7.1.2 Triannual Maintenance .....................................................................................................19
7.1.3 Annual Maintenance.........................................................................................................19
SPECIFICATIONS ............................................................................................................21
WARRANTY......................................................................................................................23

Model 20981 UHF Data Radio User’s Manual
1
1. OVERVIEW
The Model 20981 UHF Data Radio is an integrated modem and radio that provides digital data
transmission at data rates of 9600 bps in a 12.5 kHz channel over a frequency range of 450–
470 MHz. The user data interface is a serial port through a 15-pin D connector, and is configured
for RS-232 signal levels. The Data Radio comes in a small, compact package that is easy to
integrate into new systems or retrofit into existing systems.
Transmit and receive LEDs provide the operational status of the Data Radio.
The antenna interface to the Data Radio is through a standard 50 Ω female BNC connector. A
variety of antennas can be used.
1.1 INSTALLATION KITS
Kits have been prepared to allow the Model 20981 UHF Data Radio to be installed in an AWOS
3000 CDP, a DCP, or as a retrofit to a previous installation using other radio modems. The kits
provide the UHF Data Radio(s), attenuator, other hardware, and cables needed for the
installation.
Table 1. Model 20981 UHF Data Radio Installation Kits
Part Number
Description
M488306-01
AWOS 3000 CDP Installation Kit
M488678-00
Retrofit Kit to replace AWOS 3000 CDP and DCP radios
M488679-00
DCP Installation Kit
1.2 FCC REGULATIONS
1.2.1 Licensing
The FCC and regulatory authorities in other countries require that the radio owner/operator
obtain a station license for the radio before using the equipment to transmit, but do not require an
operating license or permit. The station licensee is responsible for proper operation and
maintenance of the radio equipment, and for ensuring that transmitter power, frequency, and
deviation are within the limits specified by the station license. This includes checking the
transmitter frequency and deviation periodically using appropriate methods.
1.2.2 Equipment Authorization (Certification)
FCC Approval had been granted for the Model 20981 UHF Data Radio in November, 2014.

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1.2.3 Radio Frequency Exposure
The FCC, with its action in General Docket 79-144, March 13, 1985, adopted a safety standard
for human exposure to radio frequency electromagnetic energy emitted by regulated equipment.
The Model 20981 UHF Data Radio has been evaluated for compliance with the maximum
exposure limits for RF energy at the maximum power rating of the unit. To ensure compliance
with the General Population/Uncontrolled maximum exposure limits, please ensure that all
persons will be at least 20.5 cm (8.1") away from the antenna.

Model 20981 UHF Data Radio User’s Manual
3
2. I/O CONNECTOR AND LED INDICATORS
2.1 I/O CONNECTOR
Table 2. I/O Connector Pinout
Pin
Name
Description
Comments
1
—
—
Not used
2
—
—
Not used
3
—
—
Not used
4
A/B
Input
Channel 1/2 or High/Low power
5
RSSI
Output
Analog Receive Signal Strength Indicator
6
Supply
Input
DC Power connects here to power unit
7
NC
Output
Receiver Alignment—DO NOT CONNECT
8
RD
Output
RS-232 data output from modem
9
TD
Input
RS-232 data input to the modem
10
CTS
Output
RS-232 clear to send output from modem
11
DSR
Output
RS-232 data set ready output from modem
12
—
—
Not used
13
CD
Output
Carrier detect
14
RTS
Input
RS-232 request to send input to modem
15
GND
System ground (power supply and signal)
2.1.1 Pinout Description
Pin 4 (A/B)
Depending on how it is programmed via the programming utility, Pin 4 can either be a Channel
A/Channel B selection pin or a High/Low transmit power selection pin. This pin has an internal
pullup resistor to +5 V and assumes a high (channel A or high power) state when left
unconnected.
Pin 5 (RSSI)
Pin 5 is an analog output whose amplitude is proportional to the signal strength of the received
signal. The voltage at this pin varies from about 1.6 VDC for a -130 dBm signal to about 4 VDC
for signals at or above -60 dBm.

Model 20981 UHF Data Radio User’s Manual
4
Pin 6 (Supply)
Pin 6 is the positive power supply input for the modem.
Pin 7 (Receiver Alignment)
Pin 7 is the output pin of the modem IC’s input operational amplifier. It is used during alignment
to set the receiver gain and DC offset for proper modem IC receiver decoding. This pin must be
left unconnected.
Pin 8 (RD Receive Data)
RS-232 data to be received from the modem are available at Pin 8. The data are at normal
RS-232 levels and are transmitted from the modem to be received by the host computer or other
device connected to the modem.
Pin 9 (TD Transmit Data)
RS-232 data to be transmitted to the modem should be presented to Pin 9. The data should be at
normal RS-232 levels and are transmitted from the host computer or other device to the modem.
Pin 10 (CTS Clear to Send)
This RS-232 output pin is asserted by the modem as a response to an assertion of the RTS pin
when it is ready and able to receive data from the host computer or device.
Pin 11 (DSR Data Set Ready)
This RS-232 output pin is asserted by the modem when it is powered-up. It indicates that the
modem is actually connected, although not necessarily ready to receive data. The polarity (active
low/active high) is programmable via the programming utility.
Pin 13 (CD Carrier Detect)
Pin 13 is asserted by the modem when the receiver has detected a carrier. The RF level for CD
assertion is set via the programming utility. Note that the modem demodulation circuitry does
not actually use this signal to determine that a valid data packet has been received. The polarity
(active low/active high) is programmable via the programming utility
Pin 14 (RTS Request to Send)
This RS-232 input pin is asserted by the host computer or device to indicate that it has data to be
transmitted by the modem. If the modem is able to accept the data, the CTS pin will be asserted
in response.
Pin 15 (GND Ground)
The system ground common point and negative connection for the power supply and RS-232
signals.

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5
2.2 LED INDICATORS
The Model 20981 UHF Data Radio has two LEDs on the side of the unit, one green RX LED and
one red TX LED.
•The GREEN RX LED can be programmed to be illuminated under a variety of
conditions. The choices are:
oNever (Off)
oWhenever power is applied (Power On)
oWhen receiving, whether or not an actual signal is on the frequency
(RX Synthesizer Lock)
oWhen receiving and an actual data packet is being received (RX Data).
In typical applications, either RX Synthesizer Lock or RX Data is selected.
•The RED TX LED can be programmed to be illuminated when the modem is
transmitting, or to be never illuminated.