ACTIVE_ANTENNA_WITH_GAIN

Published:2009/7/8 22:20:00 Author:May | From:SeekIC

The signal boostei，built around a few transistors and support components，offers an RF galn of about12 to 18 dB (from about 100 kHz to over 30 MHz). The RF signal is direct－coupled from Q1’s Source terminal to the base of Q2，which is configured as avoltage amplifier． The output of Q2 is then direct－coupled to the base of Q3 (configured as an emitter-fallower amplifier)．Transistor Q3 is used to match and isolate the gam stage from the receiver’s RF-inputcircuitry． Inductor L1 is used to keep any power Source nolse from reaching the FET (Q1) and any value of RF choke from 0.5 to 2.5 mH will do.The value of R2 sets the Q2 bias at about 2V. If the voltage is less than 2V, Increase the value of R2 to 1.5 kΩ，To go below 100 kHz(to the bottom ofthe RF spectrum)，increasethe value of C1 to 0.002 μF. The antenna is a short pull－up type (42″to 86″long)．



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