The ST-940B Mobile HF NVIS Magnetic Loop Antenna has been developed to address the emerging need to reduce the visibility of vehicles fitted with traditional HF antenna systems.
Earlier, the presence of large HF Whip or auto tune vehicular antenna used to make vehicles an easy target But, the unique design of the ST-940B provides for a hidden, almost undetectable presence of en efficient antenna system on the vehicle, which is camouflaged by shaping it as a regular luggage roof rack.
The highly efficient auto tune antenna radiates with an almost vertical take-off angle. It provides reliable communication within distances that are traditionally affected by skip zones created by the radiation pattern of non-NVIS antennas.
A closed H/Q loop circuitry ensures significant increase in transmitting end receiving power as well as reception immunity to ignition and industrial noise. Compared with the traditional whip-type vehicle antennas, the ST-940B gives an additional 9dB of omni-directional gain, even in regions with poor soil conductivity. As a result, the overall performance of the entire vehicular HF installation is now much higher than other vehicle antenna systems.
The ST-940B antenna is skillfully modeled with extensive use of NEC CAD software. The roof rack has been meticulously designed to become an integral part of the antenna system rather than building the antenna around a random rack. The fully functional roof rack can also be used for carrying almost any kind of cargo, except fuel and light flammables.
The all-welded lightweight aluminum construction provides physical strength, excellent tuning point stability and protects the mechanical parts of the antenna from damage. Made to the highest quality standards and with extensive knowledge of materials, the construction is free of environmental problems such as corrosion due to dissimilar metal joints, UV degrading, low temperature cracking and dehermitisation.
The shock-sensitive components of the system are protected by aircraft-type shock absorbing vibroframe. The micro-processor controlled interface of the Stealth ST-940B allows for flexibility in connection with any type of mobile HF transceiver.
HF Magnetic Loop Key Features
Power Rating - The antenna is rated for a maximum RF power of 150W PEP
Fully Automatic Operation - The motorized folding loop can change its position within seconds from inside the moving vehicle at any time. The antenna is designed so that it normally operates when the hinged loop is raised. However to support ALE/CALM and other networking functions of modern transceivers, the antenna can work for reception even when the loop is folded down. This feature allows for the vehicle to maintain a "hidden look" till transmission is required
Multipurpose Graphic Remote Control - The rugged construction of the antenna remote control unit allows control and observation of the current antenna position and tuning parameters,through large, easily readable mnemonic symbols and messages on the bright OLED display that is installed on the vehicle's dashboard
Intelligently Designed User Interface - It allows customers to change warning sound signals as well as provides computerized access for radio technicians to the system parameter settings and diagnostics
Easy Installation and Operation - The Antenna is easily installable on the hard roof of vehicles, end bothinstallation & operation does not require highly qualified radio personnel
20 kHz at 3.0 MHz Carrier 260 kHz at 15D MHz Carrier
Power Supply Voltage
12-18VDC/ 4 A [peak current]
ATU Tuning Method
Continously Variable Tuning
Tuning Drive Method
WC/stepper motor/mute ble chopper drive/VSWR bridge/CPU
Tuning Time
3 seconds average, Â seconds max.
Tuning Accuracy
± 1.8° step or Approx. +200 Hz at 3.0 MHz Approx. ±15 kHz at 14 MHz
Tune Signal
(Default settings
compatible with
Codan NGT
series transceivers)
Programmable consequence vide upto 4
bi-directional logic ports, followed by 10-30 W PEP CW
Tune Point Instability vs
WInd/Vibration
Tune Point Instability
vs Heat/Time messured,
within 3 minutes
under 100 W PEP CW
Not detected at speeds up to 150 km/h asphalt and up to 90 km/h offroad
Less then 500Hz negative drift @ frequencies below 4 MHz
Less than 10Hz negative drift @ frequencies above 4 MHz
VSWR matching
Gamma-match/reactance bank
System Serial Bus
RS-485, differential
Programming Port
RS-232
Dimensions H x W x L,
(without
mounting brackets)
Folded Up: 740* * x 1254 x 1852 mm
Folded Down: 175 x 1254 x 1B52 mm
Weight (without
mounting brackets)
36 kg
Sealing
Withstands rain testing per MIL STD 810 C/D/E
Shock/Vibration
Protection provided via Impact resistant vibroframe
Dust and Humidity
Protection provided via environmental resistant housing
to ML STD 810 C/D/E and connections to MIL C26482
Data is specified for +25oC unless otherwise stated. Star marked data is tentative.
** - For ST-940B only. Specifications are subject to change without notice and are issued for guidance purposes only.
Accessories & Options
ST-940 Standard Package includes:
94010.10 Roof Rack Antenna Assembly
94020.10 Automatic Tuning Unit
94030.10 Main Unit
94040.10 Junction Unit
94050.10 Remote Control Unit
94060.10 Cable Set
94070.10 Configuration/Diagnostic6 Software CD and User's Manual
ST-940 options (select one when ordering):
94080.10 - Wide Roof Bracket Set. Fitting for rain shield type roofs. Vehicles supported includes Mercedes Benz G-CIaaa Gelendewagen, Nissan Patrol 19B9, etc. Also fits certain sedans, minivans and pickups.
940B1.10 - Tall Ceiling Roof Bracket Set Fitting for rain shield type roofs. Vehicles supported includes Landrover Discovery, Long/Short 110/90 County Station Wagon. It can also fit certain other vans, trucks and pickups.
94082.10 - Slot Type Roof Bracket Set. Fits post 2000 Toyota Land Cruiser, Nissan Patrol. Mercedes-Benz ML - series, etc. Also fits some modern sedans and 4x4s.
94090.00 - Spare Parts & Custom Software.
Note: Some vehicles such as the Hummer may or may not require special design brackets. Please provide the outline drawings of the roof or contact us for more details.
