1/4 wavelength Active Antenna

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.

1/4 wavelength Active Antenna Circuit Diagram
 

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.
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