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The concept of the Dressler ara 2000

A typical problem encountered with modern wideband VHF/UHF receivers is the choice of a suitable antenna. A common choice is the popular discone design. However, the major drawbacks of the discone are its size and its lack of a very wide frequency range. A solution to these shortcomings is the Dressler ara 2000 active antenna, offering advantages such as very good impedance matching to the receiver, plus a very wide frequency range and a compact design.

Modern receivers are not as sensitive as we often would like them to be. Typically, most receivers have a noise figure of 5-8 dB, which describes their sensitivity. The ara 2000 helps to improve the sensitivity by 2-4 dB, which is a remarkable increase in the signal-to-noise ratio.

The ara 2000 offers a very important advantage over passive antenna systems: The low noise amplifier in the antenna increases the signal before any cable losses are introduced. Depending on the cable length used, the additional improvement in reception can be 5-8 dB! This means signals which were normally below the noise floor can now be picked up and clearly heard!

The electronic design of the ara 2000 utilizes modern profession techniques. The modified conical antenna structure allows for very wideband reception and can pick up signals in both the vertical and horizontal fields, although vertical polarization is preferred. The active section employs a state of the art MMIC (Monolithic Microwave Integrated Circuit) preamplifier with a very low noise figure, followed by a high current final stage for maximum strong signal handling performance. To match the gain of the antenna to the receiver in use and prevent overloading, a variable attenuator (0 to -20 dB) is incorporated into the remote interface unit that is situated near the receiver.

The antenna element and the electronics are housed in a solid plastic tube less than 18 inches tall and 3.5 inches in diameter, making the ara 2000 very unobtrusive and resistant to harsh enviormental conditions. The large volume inside the tube ensures adequate heat dissipation of the power produced by the high current wideband amplifier module. The ara 2000 antenna tube can be mounted to any metallic or non-metallic mast by means of two supplied mounting brackets. P> Power for the antenna electronics is supplied via the coaxial cable by a 12 volt DC source (optional) connected to the indoor interface unit. The ara 2000 is supplied with approx. 40 ft. of RG-58U coaxial cable, but up to 130 ft. can be used if suitable cable is chosen (i.e., Belden 9913). A BNC connector is supplied at the receiver end.

 

Active Antennas versus Longwire Antennas

On the VHF and UHF bands, a remote passive antenna such as a discone is subject to severe feedline losses, resulting in weaker signals at the receiver's antenna input. The integrated low-noise amplifier of the ara 2000 increases signal strength before any cable losses are encountered, delivering much stronger signal levels to the receiver.