This is for not suitable for external use. This appears to be the same unit as used for the AD270 and AD370 units. Interface/Preamp Model IB5.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.An Active Short Dipole Antennawith Remote TuningThe last active dipole aerial produced so far came from Datong (the AD-370) some 30. AD370 was designed for outdoor use. AD270 was the indoor version. The antenna consists of three.There were two later versions of the wideband active antenna.
![]() ![]() Datong Active Antenna Model Ad370 Zip Cord ForThis pro-vides the best possible immunity from strongcommon-mode signals and also allows for theelimination of the 220K gate biasing resistors,which in turn provides a very high load imped-ance for the short dipole antenna. To start with, we adda BalBal transformer between the antenna in-put terminals and the JFET gates, as shown inthe functional schematic of Fig. 1 is avery good place to begin. It also requires that a separate con-ductor be provided for supplying DC power,which is an unnecessary installation burden.An Improved Balanced ActiveDipole Antenna AmplifierThe Lankford circuit has little if anything tooffer as a basis for an efficient and effectivedesign, however the balanced feedback topol-ogy of the Datong circuit shown in Fig. 3 - Basic BalancedActive Dipole AmplifierUse of table lamp zip cord for transmission lineis highly questionable if for no other reason thanthe very high dielectric losses in the insulationmaterial. Neo geo cd emulator for macThe am-plifier gain is now controlled by the turns ratioof transformer T2. 4 - Active Short Dipole Antenna Amplifier with Remote TuningActeristics of the amplifier remain essentiallythe same as before, however the higher openloop gain provides significantly better IMD char-acteristics for the JFET input stage. The output impedance char-C1, C2, C3, C4, C6, C8 - 0.1uFC5 - 22uF 16V electrolyticC7 - 0.33uF 50V electrolyticD1, D2 - MVAM109 or MVAM115 (see text)D3 - 1N5236BQ1, Q2 - J309 or J310 (preferred)Q3, Q4 - 2N2222 or MPS6521 (preferred)R2 - 10KR3, R4 - 100 ohms (see text)R5, R6 - 470 ohmsR7 - 12 ohmsT1 - 1:2CT Transformer (see text)T2, - 2:2:12 Transformer (see text)T3 - 1:2 Balanced Autotransformer (see text)T4 - 1:1 Balun Transformer (see text)Fig. These may be changedas desired if a different bias condiciton is de-siredRather than have two separate gainstages as with the Datong amplifier, the JFETand bipolar devices are combined into a sin-gle non-inverting stage having a very hightransconductance. This turns ratio provides a noise-and distortion-free voltage gain of 2.Trask, Active Short Dipole Antenna 5 7 March 2011The JFET biasing resistors R3 and R4are chosen to provide about 5-10mA of biascurrent for each device. ![]()
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