| AS-154A/URD-4 |
|
| Physical
Dimensions |
|
| Height |
73
- 1/16 inches |
| Diameter |
18
- 3/4 inches |
| Weight |
72.75
lbs |
| Operating
Temperature |
-54
C to +65 C |
|
|
| Frequency
Range |
225
to 400 MHz |
| Input
Impedance |
50
ohms (nominal) |
| VSWR |
Unavailable |
| Polarization |
Vertical,
designed to furnish satisfactory azimuth information
where received signals are 45 degrees from vertical |
| RF
Power Rating |
n/a,
receive only |
| Power
Requirement |
Control
voltages supplied from OA-485A/URD-4 Receiver Group |
| Feed
Type |
Unbalanced,
coaxial cable |
| Input
Connector |
RF:
UG-271/U
Control:
10-42224-7P |
|
|
Description:
The AS-154A/URD-4 is a unit ofthe AN/URD-4 series UHF
Direction Finders. The antenna is a rotating Adcock array
employing two dipoles positioned vertically and protected by
a plastic radome. The sense relay is also located within the
radome. The lower antenna housing encloses the antenna drive
motor, balun transformer, tone wheel and al ternator. The
antenna control and RF cables are connected to the antenna
assembly through connectors at the base of the antenna
housing. The AN/ URD-4 is used to provide visual direction
finding information within its frequency range.
Installation: The antenna should be mounted
high enough to clear obstructions and reflecting surfaces in
its immediate vicinity so as to minimize signal reflections
and unequal signal pick-up. The base of the antenna assembly
has eight 3/8 inch bolt holes on a 7 - 3/4 inch bolt circle
for mounting the antenna to the ship's structure. The
maximum cable length between the antenna and receiver is
limited to 150 feet. The antenna must be oriented in the
direction of the ship's bow in accordance with the arrow
stamped on the antenna housing.
Considerations: The base of the antenna
assembly is fitted with a drain plug and vent hole to allow
pressure equalization and drainage of accumulated
condensation caused by atmospheric temperature variations.
The antenna may be pressurized to 1 lb. psig, with dry air
by replacing the drain plug with a 1/8 inch AN hydraulic
fitting and connecting to an air pressure line. |
