Posted on Feb 2, 2013

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.

Click here to download the full size of the above Circuit.

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.

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