the distortion in the baseband output highly depends on the source resistor and the amplitude and bias at the gate. It improved quite a bit in the end when the potentiometer was used instead of the 22k. It would be nice to see the THD or at least the FFT of the base band output and adjust the source resistor to minimize the THD. It's a FET so the second harmonic distortion is dominant
Good idea and good timing: Measuring THD is going to be a topic of a future video, so I will consider actually using the Infinite Impedance Detector as a device under test. Migth actually be interesting to even compare regular diode detector, with and without bias, and JFET-based options against each other in regards of THD performance. So thanks for your suggestion.
I have always been curious about this type of detector. I am currently in the process of building a communications receiver and at this point the detector is a diode type in which I have the diode slightly forward biased to overcome the problem of the .6 Volts of signal needed to get the diode to conduct. I never liked the low signal detect/no detect problem. So I am wondering how the infinite impedance detector performs at low signal input levels. Could you tell me about your findings regarding this aspect?
Hey Mark, it's been a while since I tried a comparison between a biased diode detector and the infinite impedance detector. But the infinite impedance detector definitely performed a lot better in low-signal conditions than the biased diode detector. The second circuit in the video with the IF transformer, for instance, works well on 200 mVpp signal amplitude.
Pretty much any n-channel JFET should work. The BF245 definitely works and I also tried a J113. You may have to adjust the source resistor, however, to bias the device into cut-off.
I am puzzled why we see both the halfwaves of the demodulated signal if, as the author said, the negative hafwave of the modulated signal does not change the conductivness of the JFET. I would be grateful for some explanation from someone knowing the right answer here.
Fantastic demonstration ❤❤
Thanks so much 😊
Great video! Thank you for sharing.
Nice and clear explanation.
Thanks!
Thats helpful, thanks!
Glad you found the video helpful! P.S. Been subscribed to you since whenever I discovered your channel.
@@BalticLab Haha, tnx!
the distortion in the baseband output highly depends on the source resistor and the amplitude and bias at the gate. It improved quite a bit in the end when the potentiometer was used instead of the 22k. It would be nice to see the THD or at least the FFT of the base band output and adjust the source resistor to minimize the THD. It's a FET so the second harmonic distortion is dominant
Good idea and good timing: Measuring THD is going to be a topic of a future video, so I will consider actually using the Infinite Impedance Detector as a device under test. Migth actually be interesting to even compare regular diode detector, with and without bias, and JFET-based options against each other in regards of THD performance. So thanks for your suggestion.
Valves is the terminology used in the UK (and probably some commonwealth countries). Tubes is the U.S. name, not sure about Canada. Fascinating video!
I have always been curious about this type of detector. I am currently in the process of building a communications receiver and at this point the detector is a diode type in which I have the diode slightly forward biased to overcome the problem of the .6 Volts of signal needed to get the diode to conduct. I never liked the low signal detect/no detect problem. So I am wondering how the infinite impedance detector performs at low signal input levels. Could you tell me about your findings regarding this aspect?
Hey Mark, it's been a while since I tried a comparison between a biased diode detector and the infinite impedance detector. But the infinite impedance detector definitely performed a lot better in low-signal conditions than the biased diode detector. The second circuit in the video with the IF transformer, for instance, works well on 200 mVpp signal amplitude.
Can I use 2SK19 or 2SK30 or BF245?
Thank you
Pretty much any n-channel JFET should work. The BF245 definitely works and I also tried a J113. You may have to adjust the source resistor, however, to bias the device into cut-off.
@@BalticLab thank you very much, sir
I am puzzled why we see both the halfwaves of the demodulated signal if, as the author said, the negative hafwave of the modulated signal does not change the conductivness of the JFET. I would be grateful for some explanation from someone knowing the right answer here.
Silly me. Of course you need only one HF halfwave to get the whole demodulated audio as it is all biased above zero level.