TIL 1792 User manual

All Weather Inc. • 1165 National Drive • Sacramento, CA 95834 • USA • 800.824.5873 • www.allweatherinc.com
User’s
Manual
Rev. B
Model1792
VHFRadio
×
FAA APPROVED
ECP202 — 2014 Dec 30
NOT FAA APPROVED

Copyright ©2011, All Weather, Inc.
All Rights Reserved. The information contained herein is proprietary and is provided solely for the purpose of
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Disclaimer
The information and specifications described in this manual are subject to change without notice.
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1792 VHF Radio User's Manual
TABLEOFCONTENTS
1. OVERVIEW.........................................................................................................................1
2. INSTALLATION AND CHECKOUT.....................................................................................2
2.1 Set Operating Frequency ............................................................................................................2
2.1.1 Remove the Bottom Enclosure Cover.................................................................................2
2.1.2 Set the Transmitter Frequency............................................................................................3
2.1.3 Replace the Bottom Enclosure Cover.................................................................................7
2.2 Mounting Bracket.......................................................................................................................7
2.3 Calibration ..................................................................................................................................8
2.4 Connections ................................................................................................................................8
2.5 Operational Check......................................................................................................................9
3. OPERATING INSTRUCTIONS .........................................................................................10
3.1 Switches, Controls, and Indicators ...........................................................................................10
3.2 Operating Instructions ..............................................................................................................11
3.2.1 Switching VHF Radio OFF ..............................................................................................11
4. MAINTENANCE................................................................................................................12
4.1 Periodic Maintenance ...............................................................................................................12
4.1.1 Monthly Maintenance.......................................................................................................12
4.1.2 Triannual Maintenance .....................................................................................................12
4.1.3 Annual Revalidation .........................................................................................................12
4.2 Voice Output Static Reduction.................................................................................................17
4.3 Fuse Replacement.....................................................................................................................17
5. SPECIFICATIONS ............................................................................................................18
6. FORMS.............................................................................................................................19
7. WARRANTY......................................................................................................................20

1792 VHF Radio User's Manual
1
1. OVERVIEW
The Model 1792 VHF Radio is a single-channel, fixed-frequency, low-power transmitter intended for
base station operation in an air traffic environment to broadcast audio automated weather observations
from the AWOS 3000. The Model 1792VHFRadio operates over the frequency range from 117.975 MHz
to 138.000 MHz, and uses DC power (negative ground only). The frequency is programmable over
the specified frequency range with a channel spacing of 25 kHz.
The Model 1792 VHF Radio includes the following items.
Mounting Bracket —A U-shaped aluminum alloy bracket is used to mount the Model 1792 VHF
Radio in the AWOS 3000 CDP rack.
Power Input Cable Assembly —A 12" (30 cm) two- core cable terminated at one end by a
two-pin (female contacts) connector mates with the two-pin (male contacts) power connector
at the back of the Model 1792 VHF Radio. The cable provides DC power from the AWOS
CDP rack.
VHF Radio Signal Cable Assembly —A 36" (90 cm) cable terminated at one end with a male
DB9 connector delivers the VHF voice output and the keying instructions that turn the
transmitter on/off. This cable connects to a female DB9 connector on the side of the Model
1792 VHF Radio.
An RG-58 antenna cable in the AWOS 3000 CDP rack connects the antenna output on the back of the
Model 1792 VHF Radio to the antenna connector on the back of the CDP rack.

1792 VHF Radio User's Manual
2
2. INSTALLATIONANDCHECKOUT
2.1 SET OPERATING FREQUENCY
The operating frequency must be set before the Model 1792 VHF Radio is used. The frequency is set
using jumpers inside the radio enclosure.
2.1.1 Remove the Bottom Enclosure Cover
To access the frequency setting jumpers, you must first remove the bottom enclosure cover.
1. Remove and set aside the 13 screws securing the bottom enclosure cover to the radio chassis.
2. Lift the cover clear of the chassis to expose the internal view of the radio as shown in Figure 1.
Figure 1. Model 1792 Internal View

1792 VHF Radio User's Manual
3
2.1.2 Set the Transmitter Frequency
The operating frequency may be programmed over the frequency range from 117.975 MHz to
138.000 MHz with a 25 kHz channel spacing.
1. Determine the operating frequency to be programmed. Jumpers on the Single-Channel
Memory Set Board (Figure 2) are used to set the frequency based on its MHz and kHz
components.
Figure 2. Frequency Set Jumpers

1792 VHF Radio User's Manual
4
2. Refer to Table 1 to select the integer portion of the frequency. Find the desired frequency in
the Operating Frequency column, and install the jumper(s) accordingly.
Table 1. MHz Frequency Selection Jumper Settings
Operating
Frequency
(MHz)
Jumper Location
20 MHz
10 MHz
8 MHz
4 MHz
2 MHz
1 MHz
117
0
1
0
1
1
1
118
1
1
1
0
0
0
119
0
1
1
0
0
1
120
1
0
0
0
0
0
121
1
0
0
0
0
1
122
1
0
0
0
1
0
123
1
0
0
0
1
1
124
1
0
0
1
0
0
125
1
0
0
1
0
1
126
1
0
0
1
1
0
127
1
0
0
1
1
1
128
1
0
1
0
0
0
129
1
0
1
0
0
1
130
1
1
0
0
0
0
131
1
1
0
0
0
1
132
1
1
0
0
1
0
133
1
1
0
0
0
1
134
1
1
0
1
0
0
135
1
1
0
1
0
1
136
1
1
0
1
1
0
137
1
1
0
1
1
1
138
1
1
1
0
0
0

1792 VHF Radio User's Manual
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3. Refer to Table 2 to select the decimal portion of the frequency. Since 0.001 MHz is 1 kHz, this
portion of the frequency is expressed in kHz in the table. Find the desired frequency in the
Operating Frequency column, and install the jumper(s) accordingly.
Table 2. kHz Frequency Selection Jumper Settings
Operating
Frequency
(kHz)
Jumper Location
800 kHz
400 kHz
200 kHz
100 kHz
50 kHz
25 kHz
000
0
0
0
0
0
0
025
0
0
0
0
0
1
050
0
0
0
0
1
0
075
0
0
0
0
1
1
100
0
0
0
1
0
0
125
0
0
0
1
0
1
150
0
0
0
1
1
0
175
0
0
0
1
1
1
200
0
0
1
0
0
0
225
0
0
1
0
0
1
250
0
0
1
0
1
0
275
0
0
1
0
1
1
300
0
0
1
1
0
0
325
0
0
1
1
0
1
350
0
0
1
1
1
0
375
0
0
1
1
1
1
400
0
1
0
0
0
0
425
0
1
0
0
0
1
450
0
1
0
0
1
0
475
0
1
0
0
1
1
500
0
1
0
1
0
0
525
0
1
0
1
0
1
550
0
1
0
1
1
0
575
0
1
0
1
1
1
600
0
1
1
0
0
0
625
0
1
1
0
0
1
650
0
1
1
0
1
0
675
0
1
1
0
1
1
700
0
1
1
1
0
0
725
0
1
1
1
0
1
750
0
1
1
1
1
0
775
0
1
1
1
1
1
800
1
0
0
0
0
0

1792 VHF Radio User's Manual
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Operating
Frequency
(kHz)
Jumper Location
800 kHz
400 kHz
200 kHz
100 kHz
50 kHz
25 kHz
825
1
0
1
1
0
1
850
1
0
0
0
1
0
875
1
0
0
0
1
1
900
1
0
0
1
0
0
925
1
0
0
0
0
1
950
1
0
0
0
1
0
975
1
0
0
0
1
1
Figure 3 shows an example of the jumper
setting for a frequency of 123.175 MHz.
Figure 3. Jumper Settings for 123.175 MHz

1792 VHF Radio User's Manual
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2.1.3 Replace the Bottom Enclosure Cover
1. Position the bottom cover on the chassis.
2. Position one screw in each corner of the bottom cover mounting holes.
3. Secure the three screws for the “inside” of the enclosure cover.
4. Secure the remaining screws in the holes around the enclosure perimeter.
2.2 MOUNTING BRACKET
The CDP rack’s bottom shelf (Figure 4) 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
the mounting bracket, with the control knobs facing to the right when the VHF radio is viewed from
the front end of the CDP rack.
Figure 4. CDP Bottom-Shelf Components
The mounting bracket and the VHF radio are installed at the factory. Should the need arise to remove
the radio, undo the wing screws 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 mounting bracket. Any cables that have been removed should be reattached before mounting
the VHF radio back in the mounting bracket.
There is no need to remove the mounting bracket itself.

1792 VHF Radio User's Manual
8
Figure 5 shows the VHF radio secured in the mounting bracket.
Figure 5. VHF Radio Secured in Mounting Bracket Using Wing Screws
2.3 CALIBRATION
The Model 1792 VHF Radio is calibrated at the factory prior to shipment, and should not need to be
calibrated again during installation. Power level and modulation calibration are performed as part of
the annual revalidation described in Section 4.1.3.
2.4 CONNECTIONS
The VHF radio is connected to existing connectors in the CDP rack as shown in Figure 6. Follow
these steps.
1. Ensure that the VHF radio’s POWER ON/OFF switch is set to OFF.
2. Connect the M491852-00 antenna cable from the VHF RG58 connector on the back side of the
CDP rear panel to the RG58 antenna connector at the back of the VHF radio.
3. Connect the M491844-00 signal cable’s DB9 connector to the DB9 connector on the side of
the VHF radio.
4. Connect the M491850-00 power supply cable to the power supply connector on the rear side
of the VHF radio. The red wire is positive, and the black wire is the negative supply ground
5. Power on the radio by switching the radio's POWER ON/OFF switch to ON.

1792 VHF Radio User's Manual
9
Figure 6. VHF Radio Connections
2.5 OPERATIONAL CHECK
Ensure that the VHF radio operates as described in the operating instructions in Chapter 3.
Section 4.2 describes how to reduce the static if it is evident in the broadcast.

1792 VHF Radio User's Manual
10
3. OPERATINGINSTRUCTIONS
3.1 SWITCHES, CONTROLS, AND INDICATORS
Figure 7 shows the switches, controls, and indicators on the front panel of the VHF radio.
Figure 7. VHF Radio Front Panel Controls
Table 3 provides a functional description of each of the VHF radio switches, controls, and indicators.
Table 3. Description of VHF Radio Switches, Controls, and Indicators
SWITCHES
CONTROLS &
INDICATORS
FUNCTIONAL DESCRIPTION
POWER ON/OFF
SWITCH
A two-position toggle switch controls the application of the power
supply to the VHF radio.
Position 1, toggle UP, the VHF radio is switched ON.
Position 0, toggle DOWN, the VHF radio is switched OFF.
POWER ON LED
INDICATOR
A green LED is ON when the POWER ON/OFF switch is set to
Position 1, and power is applied to the VHF radio.
FUSE
A 5 A fuse which protects the power supply line.
As part of reverse polarity protection, the fuse will “blow”if the
polarity of the supply line is reversed.
FUSE BLOWN
RED LED
INDICATOR
A red LED goes ON when the 5 A fuse is “blown”while power is
applied to the VHF radio.

1792 VHF Radio User's Manual
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SWITCHES
CONTROLS &
INDICATORS
FUNCTIONAL DESCRIPTION
SQUELCH
CONTROL
The unlabeled squelch control above and to the right of the fuse is not
used, and should remain in the fully counter clockwise position.
SQUELCH
INDICATOR
GREEN LED
The squelch indicator LED above the unlabeled squelch control should
remain off since the squelch control is not used.
Tx ON
YELLOW LED
INDICATOR
A yellow LED is ON when the VHF radio is transmitting. The Tx ON
yellow LED is OFF at other times.
VOLUME
CONTROL
The volume control to the right of and below the Tx ON LED is not
used, and should remain in the fully counter clockwise position.
MIC/PTT
CONNECTOR
The MIC/PTT connector below the unlabeled volume control is not
used.
SPEAKER/
HEADPHONE
CONNECTOR
The speaker/headphone connector next to the MIC/PTT connector is
not used.
3.2 OPERATING INSTRUCTIONS
1. Ensure that the signal and antenna cables are connected.
2. Set the POWER ON/OFF switch to ON.
3. Verify that the POWER ON green LED is ON.
4. Verify that the AWOS station voice message is being transmitted.
5. Ensure that the Tx ON yellow LED cycles ON during voice message output.
6. Verify that the Tx ON yellow LED cycles OFF between voice message broadcasts.
3.2.1 Switching VHF Radio OFF
1. Set the POWER ON/OFF switch to OFF.
2. Verify that all indicator LEDs on the front panel are OFF.
CAUTION
Antenna must be connected to VHF radio before turning power on.

1792 VHF Radio User's Manual
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4. MAINTENANCE
The Model 1792 VHF Radio requires no maintenance, other than the recommended periodic checks
outlined below. If transmission problems should arise, perform the Annual Revalidation procedures
described in below. If the problem persists, contact All Weather, Inc. Customer Service.
4.1 PERIODIC MAINTENANCE
Periodic maintenance of the Model 1792 VHF Radio is divided into three categories within the
maintenance cycle: monthly, triannual, and annual maintenance procedures.
4.1.1 Monthly Maintenance
Check the cabling for integrity. Verify the voice output. Verify the Tx LED illuminates when voice
output is activated.
4.1.2 Triannual Maintenance
Triannual maintenance of the VHF radio is identical to that specified in the monthly maintenance
procedure.
4.1.3 Annual Revalidation
The following list gives the test equipment required during annual revalidation.
Radio Test Equipment:
Power Meter
Bird Watt Meter Model 43 or equivalent
Forward/Reflected Power
Tester
Bird Watt Meter Model 43 w/ 10C elements or equivalent
Frequency Meter
Aeroflex 3500 or equivalent
Modulation Meter
Aeroflex 3500 or equivalent
Deviation Meter
Aeroflex 3500 or equivalent
When VHF antenna cables are longer than 50 feet, tests must be repeated at the antenna end of the
cable.
Power Level
1. Remove power from the VHF radio by turning the power switch on the radio’s front panel off.
2. Connect the power meter between the RG58 connector on the front end of the CDP rear panel
and terminate with the antenna or a dummy load. See Figure 8.

1792 VHF Radio User's Manual
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Figure 8. Insert Power Meter Between Antenna Cable
and CDP Back Panel VHF Connector
3. Apply power to the VHF radio by turning the power switch on the radio’s front panel on.
4. Record the VHF radio output power level on the Annual Technical Performance Record.
5. Turn the VHF radio power off, remove the power meter, and reconnect the antenna cable to
the RG58 connector on the front end of the CDP rear panel.
VSWR (at transmitter)
If RF cables must be disconnected when switching between power level and VSWR tests, turn the
radio off using the switch on the radio’s front panel.
1. Disconnect the M491852-00 antenna cable from the back of the VHF radio.
2. Connect a VSWR or forward/reflected power tester to the antenna connector on the back of the
VHF radio.
3. Measure the VSWR and enter the value on the Annual Technical Performance Record. If you
measure forward and reflected power, calculate the VSWR using the following equation.

1792 VHF Radio User's Manual
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VSWR
1reflectedpower
forwardpower
1reflectedpower
forwardpower
Sample Calculation:
Reflected power = 0.02 W
Forward power = 2.5 W
1964.1
9106.0 0894.1 0894.01 0894.01
008.01
008.01
5.202.0
1
5.202.0
1
_
_
1
_
_
1













powerforward powerreflected
powerforward powerreflected
VSWR
4. Disconnect the VSWR or forward/reflected power tester from the antenna connector on the
back of the VHF radio.
Frequency
If RF cables must be disconnected when switching between frequency and modulation tests, turn the
radio off using the switch on the radio’s front panel.
1. Log the assigned frequency on the Annual Technical Performance Record.
2. Connect a frequency meter to the antenna connector on the back of the VHF radio.
3. The radio transmits for approximately 30 seconds, followed by an off time of five seconds.
While the radio is transmitting, measure the frequency.
4. Record the frequency on the Annual Technical Performance Record.
5. Disconnect the frequency meter from the antenna connector on the back of the VHF radio.
CAUTION
Use isolators or attenuators as needed to protect the test equipment.

1792 VHF Radio User's Manual
15
Modulation
If RF cables must be disconnected when switching between frequency and modulation tests, turn the
radio off using the switch on the radio’s front panel.
1. Log in as an administrator on the CDP display and insert an AWOS Security Key CD. You
will be able to access the menus once the optical drive light stops blinking, indicating that the
AWOS Security Key CD has been read.
2. Connect a modulation meter to the antenna connector on the back of the VHF radio. Set the
modulation meter to the instantaneous mode.
3. Access the Edit > Configuration > Voice tab on the CDP display and click the 300 Hz tone
option in the Test panel.
CAUTION
Use isolators or attenuators as needed to protect the test equipment.

1792 VHF Radio User's Manual
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4. Use the modulation adjustment potentiometer on the VHF radio to adjust the modulation depth
to 90%.
Figure 9. VHF Radio Modulation Adjustment Potentiometer
5. Use the VHF adjustment potentiometer (R29) on the CDP peripheral interface board to lower
the signal level until the modulation decreases to 80%.
Figure 10. VHF Adjustment Potentiometer on CDP Peripheral Interface Board
6. Use the modulation adjustment potentiometer on the VHF radio to adjust the modulation depth
to 60%.
7. Set the modulation meter to the “peak hold” mode.

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8. Access the Edit > Configuration > Voice tab on the CDP display and click the Modulated 300
Hz tone option in the Test panel.
9. Reset the modulation meter and wait until the modulated tone stops.
10. Verify that the peak modulation reading does not exceed 95%. If it does, adjust the modulation
adjustment potentiometer on the VHF radio and recheck the peak modulation reading.
11. Access the Edit > Configuration > Voice tab on the CDP display and click the Word option in
the Test panel.
12. Reset the modulation meter and wait until the words stop. Verify that the peak modulation
reading does not exceed 95%. If it does, adjust the modulation adjustment potentiometer on
the VHF radio and recheck the peak modulation reading.
13. Enter the final modulation meter reading on the Annual Technical Performance Record.
14. Turn the VHF radio off using the front panel switch. Disconnect the test equipment and cables,
and reconnect the M491852-00 antenna cable. Turn the radio on.
15. Remove the CD Key from the CDP optical drive.
4.2 VOICE OUTPUT STATIC REDUCTION
The Model 1792 VHF Radio has been adjusted for use with the AWOS 3000 to minimize audible
static on the voice transmission. The following steps described how to reduce static should additional
adjustment be required.
1. Adjust the VHF voice output signal at the CDP peripheral interface board by adjusting trim
potentiometer R29 (see the Modulation section above) until the desired reduction in static is
achieved.
2. Adjusting the VHF voice output signal will also change the modulation level. Increase the
modulation level as described in the Modulation section above.
4.3 FUSE REPLACEMENT
A 5 A fuse is located on the front panel of the Model 1792 VHF Radio. Check this fuse first if the
VHF radio should fail, and replace as necessary with an appropriately rated replacement.