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I built a CW receiver using NE602 for the 20m band. Unfortunately, I do not receive any CW or SSB signals, only some noise and sometimes broadcast stations.

The schematic here shows the circuit that I built. What is wrong in the oscillator and input stages of ic that can not focused on 14 - 14.35 mhz (20m amateur band)

In oscillator section as you see i used two 220pf capacitor that are in series with each other so the total capacitance is equal to 110pf . For resonance at 14 mhz with present inductor (1uH) we need a capacitor value 129pf using formulae: (C=1/39.5 * F^2 * L) so if the varactor diode can induce about 19pf , the work is done (110+19=129) the second image show the internal transistor of ne602 chip and relationship between pins 6 and 7 and the other parts of oscillator section (https://i.stack.imgur.com/e1HLp.jpg)enter image description hereenter image description here

Mike Waters
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Farshad mahmoodi
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    Welcome to the site. You wrote that you receive only "HF". Since 20M *is* HF, that makes sense. Perhaps you can clarify? – mike65535 Sep 15 '18 at 13:52
  • Thank you for adding the details! :-) Perhaps someone here that's smarter (and with more time) than me will help you. – Mike Waters Sep 15 '18 at 22:29
  • Thank you for your attention. Infact these problems and abnormal behavior of circuits will cause to increase my electronic knowledge and finding good friends like you – Farshad mahmoodi Sep 16 '18 at 10:04

1 Answers1

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In your schematic, there is no way that the IC can get any power because:

  1. DC cannot flow through capacitors. I suggest that you look at a NE602 data sheet.

  2. There is no power being applied to pin 8.

I assume that you are receiving broadcast stations, digital transmissions, etc. Without power to the IC, it's just acting as an AM detector.

Mike Waters
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    @Farshadmahmoodi Understood. Unless someone else sees something that I didn't, it appears that you might have to show us your entire circuit. Perhaps photos of both sides of your printed circuit board would help. – Mike Waters Sep 15 '18 at 15:57