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How are you measuring it - with an ohm meter? While it's possible you have defective units, it's very common for there to be some kind of matching network at the input to the antenna. You need to test with a VNA or other RF device to be sure.


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This design pattern is called a "Tuned Radio Frequency" receiver. Almost all of the "radio" aspects of the circuit are on the far left. The antenna, capacitor, and transformer create a band-pass filter who's output goes into the diode-capacitor G1/C3 combination. This is a classic envelope detector, as the previous poster indicated. The ...


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Andy is correct that you need gain but his estimate of gain is incorrect. The gain is only 30 +/-5 with such a low bias current from 1M5 to amplify say a 50mVp to 300mVpp. The dual Sch. Diodes clamp and rectify the signal but drop about 50mV each at this xx nA current level leaving about 200 mVdc for the ADC to decide when to enable and disable mic for ...


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why do I need such a complicated circuit with Q17, D21 Q17 has a voltage gain of of several hundred so, if your input signal is not tiny you can dispense with that amplifier stage. But you can't get rid of the 2nd diode in D21 to ground after C109 because it (and the other diode) are needed to properly rectify a signal and sustain an output DC level that is ...


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The N210 is daughterboard based. That is, the N210 itself is a fancy network connected digitizer (ADC/DAC + FPGA + ethernet interface) and it requries a front-end card for analog interfacing. In most cases, this is some type of direct-conversion radio receiver, but there are also simple frontends which just provide a direct interface to the ADC and/or DAC. ...


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I found this circuit from wikiHow that is about a demodulator using opamp: https://www.wikihow.com/Create-a-Simple-AM-Radio?amp=1


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Is such a power limiter realized with an attenuator Usually no, as an attenuator would attenuate all signals so that means your receiver would become less sensitive. You actually want a "smart" attenuator that doesn't attenuate small signals but that does attenuate large signals. Note that the large (harmfull) signals aren't the ones that you're ...


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