An RF signal strength meter is a device used in radio electronics, that helps to detect the strength of an incoming radio signal in a radio receiver. It differs from a field strength meter, where it measures the strength of the radio frequency field near a radio transmitter. An RF signal strength meter shows the nature of the incoming radio signal in a radio receiver such as signal strength, fading, signal drifting, overlapping, presence of background noise etc. The signal strength is indicated by the LEDs in a linear fashion. The weak signals are indicated by the lower values of the meter such as glowing of the green LEDs and stronger signals are indicated by glowing of the red LEDs.
Working of an RF Signal Strength Meter
The RF signal input to the meter is given from the last IF amplifier section of the receiver through a low value coupling capacitor. The RF signal is then amplified by an RF amplifier stage. This amplified AC signal is then converted to DC voltage using two 1N4148 diodes. The fall and rise time of this varying signal is maintained using a timing circuit consisted of 1 Mfd capacitor and 10K ohm resistor. The DC output from this stage is given to the 5th pin of the LM3914 Dot/Bar display driver IC. This IC senses the analog voltage levels at the input and drives 10 number of LEDs thereby providing a linear analog display. The LEDs glow according to the strength of the input radio frequency signal. This IC can display the intensity of the incoming RF signal in a dot or a bar graph. The IC runs on a voltage between 3 V to 12 V. The signal input can be adjusted using a 4.7K ohm potentiometer in series with the input capacitor.
Applications of RF Signal Strength Meter
RF signal strength meter is used in radio receivers to understand the signal pattern of a station such as signal strength, fading, signal drifting, overlapping etc.
The RF signal input to the meter is given from the last IF amplifier section of the receiver through a low value coupling capacitor. The RF signal is then amplified by an RF amplifier stage. This amplified AC signal is then converted to DC voltage using two 1N4148 diodes. The fall and rise time of this varying signal is maintained using a timing circuit consisted of 1 Mfd capacitor and 10K ohm resistor. The DC output from this stage is given to the 5th pin of the LM3914 Dot/Bar display driver IC. This IC senses the analog voltage levels at the input and drives 10 number of LEDs thereby providing a linear analog display. The LEDs glow according to the strength of the input radio frequency signal. This IC can display the intensity of the incoming RF signal in a dot or a bar graph. The IC runs on a voltage between 3 V to 12 V. The signal input can be adjusted using a 4.7K ohm potentiometer in series with the input capacitor.
Applications of RF Signal Strength Meter
RF signal strength meter is used in radio receivers to understand the signal pattern of a station such as signal strength, fading, signal drifting, overlapping etc.
- It helps to assess the signal received and to send a signal report.
- It is used to check the output signal strength of an oscillator or VFO.
- It is used to tune and align the tuned circuits or tuned amplifier stages.
- It can be used as a test equipment for checking the RF signal strength at various stages of a radio receiver or transmitter.
- It can be used to study the band condition by repetitive monitoring of stations at specific intervals.
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