Thursday, January 17, 2013

Stealth ST-940B Mobile HF NVIS Magnetic Loop Antenna

The Stealth 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 NVIS Mobile loop 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 of the ST-940B HF Mobile antenna 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 dehermetization.
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.

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 both installation & operation does not require highly qualified radio personnel.

More Info; Click Here
http://www.stealth-tele.com/plugins/custompages/detinf.php?id=372&id_categories=156



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HOW TO READ PROPAGATION NUMBERS

The A index [ LOW is GOOD ]

  • 1 to 6 is BEST
  • 7 to 9 is OK
  • 11 or more is BAD

Represents the overall geomagnetic condition of the ionosphere ("Ap" if averaged from the Kp-Index) (an average of the eight 3-hour K-Indices) ('A' referring to amplitude) over a given 24 hour period, ranging (linearly) typically from 1-100 but theoretically up to 400.

A lower A-Index generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; a low & steady Ap-Index generally suggest good propagation on the 30, 40, 60, 80, & 160 Meter Bands.

SFI index [ HIGH is GOOD ]

  • 70 NOT GOOD
  • 80 GOOD
  • 90 BETTER
  • 100+ BEST

The measure of total radio emissions from the sun at 10.7cm (2800 MHz), on a scale of 60 (no sunspots) to 300, generally corresponding to the sunspot level, but being too low in energy to cause ionization, not related to the ionization level of the Ionosphere.

Higher Solar Flux generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; Solar Flux rarely affects the 30, 40, 60, 80, & 160 Meter Bands.

K index [ LOW is GOOD ]

  • 0 or 1 is BEST
  • 2 is OK
  • 3 or more is BAD
  • 5 is VERY VERY BAD

The overall geomagnetic condition of the ionosphere ("Kp" if averaged over the planet) over the past 3 hours, measured by 13 magnetometers between 46 & 63 degrees of latitude, and ranging quasi-logarithmically from 0-9. Designed to detect solar particle radiation by its magnetic effect. A higher K-index generally means worse HF conditions.

A lower K-Index generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; a low & steady Kp-Index generally suggest good propagation on the 30, 40, 60, 80, & 160 Meter Bands.

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