All Weather Inc 1793 User manual

All Weather Inc. • 1165 National Drive • Sacramento, CA 95834 • USA • 800.824.5873 • www.allweatherinc.com
User’s
Manual
Rev. A
Model1793
VHFRadio
FAA APPROVED
ECP232 —2017 Jul 28
NOT FAA APPROVED

Copyright ©2016, All Weather, Inc.
All Rights Reserved. The information contained herein is proprietary and is provided solely for the purpose of
allowing customers to operate and/or service All Weather, Inc. manufactured equipment and is not to be released,
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Disclaimer
The information and specifications described in this manual are subject to change without notice.
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1793 VHF Radio User's Manual
TABLE OF CONTENTS
1. INTRODUCTION.................................................................................................................1
1.1 Description..................................................................................................................................1
2. INSTALLATION AND CHECKOUT.....................................................................................1
2.1 Setting the Transmitter Frequency..............................................................................................1
2.2 Mounting Bracket.......................................................................................................................3
2.3 Connections ................................................................................................................................5
2.4 Calibration ..................................................................................................................................7
2.5 Operational Check......................................................................................................................7
3. OPERATION.......................................................................................................................8
3.1 Operating VHF Radio Instructions.............................................................................................8
3.2 Switching VHF Radio OFF........................................................................................................8
4. MAINTENANCE................................................................................................................11
4.1 Periodic Maintenance ...............................................................................................................11
4.1.1 Monthly Maintenance.......................................................................................................11
4.1.2 Triannual Maintenance .....................................................................................................11
4.1.3 Annual Revalidation .........................................................................................................11
5. SPECIFICATIONS ............................................................................................................20
6. FORMS.............................................................................................................................21
7. WARRANTY......................................................................................................................23

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1. INTRODUCTION
This publication provides general information on the Model 1793 VHF Radio. The Model 1793
VHF Radio is a single channel, fixed frequency Amplitude Modulated (AM) transmitter
operating over the frequency range of 118.000 to 136.975 MHz. The transmitter is intended for
base station operation in an air traffic environment. The Model 1793 operates on DC voltage in
the range of 11.25 to 16.25 volts.
1.1 DESCRIPTION
Each Model 1793 VHF Radio consists of a transmitter board mounted in a heat sink as shown in
Figure 1. The transmitter is a low power VHF AM transmitter which can transmit on a single
programmable synthesized frequency, with 25 kHz channel spacing in the frequency range of
118.000 to 136.975 MHz. The channel selection switches are accessible below the heatsink. The
transmitter requires a DC Power input that supplies voltage to the transmitter and linear
amplifier.
Figure 1. VHF/AM Single Channel Transmitter

1793 VHF Radio User's Manual
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2. INSTALLATION AND CHECKOUT
Before using the VHF Radio, it is necessary to set the operating frequency.
2.1 SETTING THE TRANSMITTER FREQUENCY
The operating frequency may be programmed over the frequency range of 118.000 to 136.975
MHz with 25 kHz channel spacing. To access the frequency jumper settings access the bottom of
the radio, opposite side of the heat sink see Figure 3. The operating frequency is selected by
setting the eleven switches on DS401 and DS402 shown in Error! Reference source not found.
and Figure 3. Refer to Figure 4 for the frequency selection switch settings. Fine-tuning the
frequency is achieved by adjusting C427.
Figure 2. Adjustments and Frequency Setting Jumpers
Figure 3. Model 1793 Bottom View

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Figure 4. Frequency Selection Switch Map

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2.2 MOUNTING BRACKET
The CDP rack’s bottom shelf (Figure 5) is fixed in place. Components are accessible through the
rack’s front or side doors. The VHF radio is secured to the bottom side of the sliding top shelf
using four wing knobs facing up when the VHF radio is viewed from the front end of the CDP
rack.
Figure 5. CDP Bottom-Shelf Components

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The mounting bracket and the VHF radio are installed at the factory. Should the need arise to
remove the radio, undo the four wing knobs on either side of the radio. Because of the tight space
inside the CDP rack, it is recommended that any connecting cables remain in place until the VHF
radio is removed from the siding shelf. Any cables that have been removed should be reattached
before mounting the VHF radio back in the mounting bracket. Figure 6 shows how the VHF
radio is secured to the siding shelf.
Figure 6. VHF Radio Secured in Mounting Bracket Using Four Wing Knobs

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2.3 CONNECTIONS
In the All Weather, Inc. AWOS 3000 system, the 1793 VHF radio is installed at the Central Data
Platform (CDP). The VHF control cable connects the VHF radio to the AWOS Peripheral
Interface PCB at terminal block J2 and the AWOS computer power supply. The cable is fitted
with a DB9 connector at one end for connection to the VHF radio. It has four unterminated wires
at the other end for connection to the Peripheral Interface. The cable also has a four pin Molex
power connector to supply power to the VHF radio from the AWOS computer power. The
antenna connector is a 50 ohm "BNC" Type connector. For runs longer than 50 feet, RG-8 cable
should be used.
To connect a 1793 VHF radio to an AWOS 3000 perform the following steps:
1. Ensure that the radio POWER ON/OFF switch is set to OFF.
2. Connect the antenna cable to the front panel BNC connector.
3. Connect the signal / power cable DB9 connector to the 9-pin D connector on the radio
front panel.
4. Connect the unterminated end of the signal cable to terminal block J2 on the Peripheral
Interface board as follows:
a. Signal cable WHITE wire to pin 1.
b. Signal cable GREEN wire to pin 2.
c. Signal cable RED wire to pin 3.
d. Signal cable BLACK wire to pin 4.
5. Connect the 4 pin connector to the AWOS computer power supply.
6. Power on the radio by switching the radio POWER ON/OFF switch to the ON position.

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Figure 7. VHF Radio Connections
Figure 8. Connector Pinout