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Showing posts with the label Antenna

Q Multiplying Loop Antenna

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 Q-Multiplying Loop Antenna Schematic Notes This circuit is designed to be used in conjunction with the standard 4 foot square loop used in MW for long distance reception. Circuit : David Sayles Email: All enquiries via anc@mitedu.freeserve.co.uk 

1 4 wavelength Active Antenna Circuit Diagram

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Circuit Diagram Description Antennas are much shorter than quarter wavelength impedance obtained is very small and highly dependent on the frequency. It was a difficult game impedances over a decade of frequency coverage. Instead, the phase of the input source-follower FET Q1. A high impedance input successfully bridges Antenna characteristics at any frequency.   transistor Q2 is used as a follower, to provide a high impedance load for Q1, but more importantly that it makes to drive low-impedance amplifier coupled to commonly Q3, which each receive a voltage amplifier. Q3 Q4 turns transistor output impedance is relatively low in impedance, which is enough to drive 50 Three dimensional receiver, Antenna input impedance. Source -http://www.free-circuit.com/2010/09/21/14-wavelength-active-antenna-circuit/

Active Short Wave Antenna

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The circuit presented here illustrates the fact that in spite of all kinds of new component and technology, it is still possible to design useful, and interesting, circuits. The circuit is based on two well-established transistors, a Type BF256C and a BF494. In conjunction with the requisite resistors and capacitors, these form a well-working antenna amplifier. Note that they are direct coupled. Transistor T1 is the input amplifier cum buffer, while the BF494, in a common-ground configuration, provides the necessary amplification. The amplifier is designed for operation at frequencies between 10 MHz and 30 MHz, which is the larger part of the short-wave range, and has a gain of 20 dB. Inductor L1 is wound on an Amidon core Type T-37-6. The primary consists of 2 turns, and the secondary of 12 turns 0.3 mm dia. enameled copper wire. The number of turns may be experimented with for other frequency ranges. The input circuit is tuned to the wanted station with capacitor C1. The response of ...

Medium Wave Active Antenna

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This circuit is designed to amplify the input from a telescopic whip antenna. The preamplifier is designed to cover the medium waveband from about 550Khz to 1650Khz. The tuning voltage required is 1 to 12 volts and can be obtained from a 10k potentiometer connected to the 12 Volt power supply. Medium Wave Active Antenna Schematic RV1 is the gain control allowing weak signals to be amplified or strong signals to be attenuated. The control voltage is applied to gate 2 of TR1, a dual-gate MOSFET, the signal voltage applied via gate 1; the input signal being tuned via L1 and the two varicap diodes at the MOSFET's input and also by L2 and the varicaps at the MOSFET's drain terminal. Both tuned circuits provide high selectivity across the entire tuning range. To aid stability the MOSFET stage is fed from a stabilized supply consisting of ZD1 and R6. To drive low impedance (50 ohm) receivers, the medium output imepedance of the BF981 stage is enhanced by the composite amplifier made f...