Smeter

Description: This design is for an external signal strength meter that is analog, digital, and audible for mobile transmitter hunters. The S meter also incorporates a gain circuit. The digital LED bar graph display has a very fast response time. The 3.3 kΩ resistor near LM3914 can be replaced with a 5 kΩ potentiometer to control LED brightness. The S2A position provides a 2:1 gain, while the S2B position offers approximately a 50:1 gain. The calibration pots regulate the meter's response relative to the gain. Additionally, an optional dampening circuit is utilized for averaging a transmitted signal that has modulated power or when dips occur on voice peaks. The capacitors can be switched individually or configured for a very slow response using a total capacitance of 5.8 µF.

The external signal strength meter is designed to provide comprehensive feedback for mobile transmitter hunters through its analog, digital, and audible outputs. The core of the meter functionality is based on the LM3914 LED bar graph driver, which allows for a visual representation of signal strength with a rapid response time. The inclusion of a gain circuit enhances the meter's sensitivity, enabling users to detect weaker signals effectively.

In the design, a 3.3 kΩ resistor serves as a fixed component that can be substituted with a 5 kΩ potentiometer, allowing users to adjust the brightness of the LED display according to their preferences or environmental conditions. This feature is particularly beneficial in varying lighting situations, ensuring optimal visibility of the signal strength readings.

The meter's gain settings are adjustable via the S2A and S2B positions, providing users with the flexibility to choose between a modest 2:1 gain and a more significant 50:1 gain. This adaptability is crucial for different hunting scenarios, allowing for precise calibration of signal detection capabilities. Calibration pots are integrated into the circuit to fine-tune the meter's response, ensuring that the displayed signal strength accurately reflects the incoming signal based on the selected gain.

An optional dampening circuit can be included in the design to smooth out fluctuations in signal strength, particularly in scenarios where the transmitted signal exhibits modulated power or experiences dips during voice peaks. This feature enhances the usability of the meter in dynamic environments, allowing for a more stable reading. The dampening circuit employs capacitors that can be switched individually, or configured collectively to achieve a total capacitance of 5.8 µF, providing a slower response time for more accurate averaging of the signal. This capability is essential for users who require consistent and reliable measurements in the field.

Overall, this external signal strength meter design combines advanced features with user-friendly adjustments, making it an invaluable tool for mobile transmitter hunters.This design is for an external signal strength meter that is analog, digital, and audible for mobile transmitter hunters. The S meter also incorporates a gain circuit. The digital LED bar graph display has a very fast response time. The 3.3-KO resistor near LM3914 can be replaced with a 5-K pot to control LED brightness. The S2A position gives a 2:1 gain and the S2B position gives about a 50:1 gain. The calibration pots control the amount of meter action relative to the gain. The optional dampening circuit is used for the averaging of a transmitted signal that has modulated power or when a dip on the voice peaks occur. The capacitors can be switched one by one or switched into a very slow response using 5.8 I"F total capacitance.