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A wonderfully simple receiver designed by Onno PA2OHH#

This receiver is a direct conversion type with two main differences from its average competitors. The receiver is designed by Onno who's website is worth checking out. Onno's website

  1. There is no variable capacitor. Instead there is a variable inductor to achieve tuning
  2. The Local oscillator (LO) runs at half the frequency of the desired frequency. That is because this radio uses a RA3AAE mixer, which the Russian Ham Radio enthusiasts used for years.

Below is Onno's circuit#

This circuit was the starting place for a YooFab kit which is still in development. Onno kindly gave permission for YooFab to make use his wonderfully simple but elegant idea. The kit will be in keeping with 'Barefoot' essence of Onno's work.

The circuit has been redrawn without notes. It is the same circuit but only contains a schematic diagram. All notes are below the diagram such that they will translate properly with the Google translate button.

M0OOZ - YooFab / CC BY-SA

40/20m receiver with RA3AAE mixer

Volume control: move L1 to/over L2

Tuning: move shortened winding L4 to/over L3

L1: 2 windings, 18 mm plastic pipe around L2

L2: 20+3 windings, 8x8 mm wooden core

L3: 25 windings, 32x32 mm wooden core

CA1 and CA2 selected for resonance at 20/40m

CB1 and CB2 selected for VFO frequency 20/40m

P1: set to minimum AM detection of BC stations

P2: set to maximum sensitivity of receiver

The bottom piece of the circuit is the variable frequency oscillator at half the reception frequency.

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