The STPS3045CW Shottky rectifier used as a variable capacitor in a shortwave radio coil oscillator

Опубликовано: 21 Январь 2024
на канале: radiofun232

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Please read the description first.

In this video the (double) Shottky diode/rectifier with type number STPS 3045 CW is used as a variable capacitor (varactor, varicap), to tune a coil (tank circuit) on Shortwave in the 3 MC range.

With a frequency variation of (say) 1 to 2 MC.

Of course the whole setup can also be used on lower or higher frequencies on Shortwave, when such a double Shottky diode is placed parallel to a coil we change the voltage on the Cathode.

The Cathode is the middle pin of the STPS 3045 CW.

All relevant information about how to use this setup is showed in the video. So it is an easy way, in my opinion, to avoid a classical tuning capacitor.

At first I told that the capacitance value of the STPS 3045 C in this showed setup must be somewhere between 10 pF and 100 pF. One day later I measured it, it is in this setup between 100 pF and 300 pF. Thanks to YT user @t1d100, asking for a calculation.

The setup is surely possible to make an analog radio oscillator work with a variation of 1 or 2 MC. That could be enough.

NEXT video (pure waveform with a FET BF 256 A oscillator, between 3 MC and (say) 6 MC or other frequencies (when you like to do radio experiments) is (23 jan. 2024) here
   • The STPS 3045 CW Shottky diode again ...

Correction: on 2.28 I say “analog audio oscillators” but of course I mean “analog Shortwave oscillators”.

FIRST video about this circuit is here
   • 1 transistor BC 547 Sine Wave (or kin...

Important: turning the 470K potentiometer sets the frequency change via the voltage to the Shottky diode and the 1 K potentiometer sets the oscillation, combined with the alignment of the 22 K bias potentiometer.

The schematic is completely OK, simple and useful.

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