The Datong AD270/370 Active Dipole Antenna One of the more popular commercially available active dipole antennas was the Datong AD270 and AD370, the former intended for indoor useage and the latter for outdoor.
![datong active antenna model ad370 datong active antenna model ad370](http://www.geocities.ws/val_alan/ra17.jpg)
1 - The Datong AD270/370 Active Dipole Antenna Amplifier Trask, Active Short Dipole Antenna 2 7 March 2011ģ meaning low NF and high IMD performance, while at the same time keeping cost and power consumption to a minimum. Typically, dipoles are designed such that their length is a half wavelength of the desired operating frequency although other lengths, although other lengths such as that for the Zepp (short for Zeppelin) are found as they have a narrower major radiation pattern. Short Active Dipole Antennas Dipole antennas share radiation pattern characteristics that are similar to those of loop antennas. The NF and IMD performance of such an amplifier constitutes the Achilles Heel of active dipole antennas, and a considerable amount of attention to detail is required in order to arrive at a suitable design the provides a high degree of dynamic range, The purpose of this paper is to present an alternative small directional antenna that is capable of both wideband and tuned narrowband perfromance and which can be made with readily available and inexpensive parts and materials. The high terminal impedance of a short dipole antenna requires that an amplifier with a similarly high input impedance be employed in order to conduct the antenna signal voltage to a suitable feedline, which is typically 50-ohm or 75-ohm coaxial cable. Also, as the dipole becomes smaller with respect to wavelength the efficiency and gain decreases, however the directional characteristics are retained, much the same as with a small loop.
#Datong active antenna model ad370 series
This is in direct contrast with the terminal impedance of a loop antenna, which is often represented as a small resistance in series with a large inductor. As the antenna becomes shorter with respect to wavelength, the impedance increases and is best represented as a large resistor in series with a small capacitor.
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A half-wavelength dipole has a terminal impedance of roughly 72 ohms. Designs that employ parallel tuning require an amplifier to couple the resultant high antenna impedance to the feed line, while those that employ series tuning can be passively matched to the feedline and have exceptional noise figure (NF) and intermodulation distortion (IMD) performance. Both forms of loop antennas require some form of tuning in order to accomodate the high inductive reactance of the terminal impedance. Small loop antennas have this characteristic, and small shielded loop antennas provide a good degree of immunity from low frequency electric field noise, which is highly desireable in urban environments. Physically small antennas that have a directional radiation pattern can be very useful when nulling out interference is desired. SWLs and radio amateurs living in confined areas such as apartments or in communities having antenna restrictions find small antennas and especially active antennas to be a practical solution.
![datong active antenna model ad370 datong active antenna model ad370](http://www.pgr1.co.uk/shackpics/pgrvp1a.jpg)
Box Tempe, AZ Senior Member IEEE Revised 7 March 2011 Trask, Active Short Dipole Antenna 1 7 March 2011Ģ Introduction Active antennas are of interest to a wide range of users, from shortwave listeners (SWLs) and radio amateurs to designers of aircraft radios.
![datong active antenna model ad370 datong active antenna model ad370](http://www.crosscountrywireless.net/active_antenna_all.jpg)
1 An Active Short Dipole Antenna with Remote Tuning by Chris Trask / N7ZWY Sonoran Radio Research P.O.