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Simple Field Strength Meter

2015-01-09 10:44  
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Circuit diagram is very useful for radio frequency (rf) engineer and hobby, especially when he had to adjust the end of the rf transmission. Circuits that use only one transistor (MPSA18) as the active component. Analog signal strength meter using the meter display (1 mA full scale). This rf field strength meter does not have absolute scale if we do not adjust the scale using a standard instrument, but this is important to rf uncalibrated meters is that you can show changes that rf field when we calibrate or antenna matching network for rf-antenna transmitter loading. If we are tuning the size of the antenna or transmitter antenna matcher-filter, then only the analog meter to get the maximum deflection. Here is a schematic diagram is rf meter circuit:

 

Field Strength Meter Simple Field Strength Meter

Circuit diagram in the picture above by transistor bias voltage of 1 mega-ohm resistor, and connected to the 1N914 diode to the ground. Voltage in the resistor-diode 0,6-0.7 about the connection V, and sent to the base of the transistor through the RFC (Radio Frequency choke) inductor. Bias voltage is required to make the transistor to conduct. Using the bias, the signal received from the antenna does not have to reach the 0.6V base-emitter barrier to make the transistor work. Bias voltage is determined by the diode below the point where the transistor started, the circuit will not take any batteries from now if there is no rf signal is received, so that does not require a power switch to cut the power consumption of the supply (battery).








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