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RF Signals Field Strength Meter Circuit

2017-08-16 10:11  
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Field strength meter is extremely useful when working with RF devices. It can be used to quickly diagnose whether a transmitter circuit is working, and can be used to detect RF signals in the environment. The simplest field strength meter could be built with a tuned LC circuit and a germanium diode, just like the way of a building a crystal radio except replacing the ear piece with a high sensitivity current meter.CI and LI resonate on the 1750 meter band, with coverage from 150 kHz to 500 kHz. LI can be slug-tuned for 160-to-190 kHz coverage alone or a 2.5 mH choke can be used for LI, if desired, using CI for tuning. A  1N270 germanium diode rectifies the RF signal and C2 is charged at the peak RF level. This dc level is amplified by anLM358 . The gain is determined by R2 and R3, 1 100-kilohm linear potentiometer that varies the dc gain from 1 to 100, driving the 50 microampere meter. This field strength meter need not be limited to LF use.The Table shows the LI and CI values for HF operation and broadband operation.LT5534 can detect RF signal from 50MHz all the way up to 3GHz, which covers most of the spectrum one typically uses. If your frequency spectrum is significantly different, you may check out the other RF detection chips the above mentioned companies offer.
 

LF or HF field strength meter