The BC547 80M SSB QRP Transceiver

An Easy To Build All Transistor Transceiver


This is a bit of a retro design, and uses easily obtained parts, no hard to find or expensive ic's (no ic's at all).

Brief Description:
   Basicly two mixers, one acting as the rx mixer/balanced modulator, the other as product detector/tx mixer.
  Q1, Q2 & Q3 form a single balanced active mixer on receive, and balanced modulator on transmit, followed by a 6Mhz
  crystal filter (Q4, Q5, Q6 & Q7). 
  Q8, Q9, & Q10 form an active product detector on receive, and balanced mixer on transmit.
  On receive, Q31 forms an active low pass filter after the product detector, and feeds into Q19 the audio preamplifier.
  Q15, Q16 & Q17 is a simple direct coupled, audio output amplifier, on tx Q29 (mute) grounds the input to the audio amplifier.
  Q18 is a simple RF amplifier ahead of the rx mixer, which is turned hard on in transmit mode to RF ground the input to the
  balanced modulator.
  Q21 is a simple AF microphone amplifier used to drive the tx modulator on transmit.
  Q13, Q14 & Q20 form the VFO.  Q13 being a standard colpitts oscillator followed by Q14 & Q20 the vfo buffer.
  Q11 is the BFO oscillator.  The VFO and BFO feed into the diode switch network D3,D4,D5 & D6 which switch the VFO and
  BFO output between the rx and tx mixer on rx and tx respectivly.  Q30,D7 & D14 form a basic voltage regulator for the VFO.
  The VFO tunes from 9.5Mhz - 9.8Mhz
  Q22 & Q23 form part of the electronic tx/rx switching circuit, as well as D11 & D10 which act as an electronic switch for the
  rx antenna.
  Q24, Q25, Q26, Q27, Q28 makeup the simple tx power amplifier with a power output of 500-600mW.
  The rx and tx bandpass filters were wound on old 10mm 455Khz IF cans, using 14 turns/2 turns.
  The mixer transformers are 10 turns trifilar wound on a ferrite bead, except  L8, which is 10 turns bifilar wound on a ferrite bead.
  The input transformer on the PA is 14 turns primary, 1.5+1.5 turns secondary (0.25mm wire) wound on a small balun core, and the
  output coil is 14 turns (0.25mm wire) trifilar wound on a larger balun core.
  All transistors used are BC547 & BC557.  In the prototype I used all BC547C types, but in the final version I used BC547B's,
  except for the PA. Using BC547B's in the PA I could only get about 300mW, after changing them to BC547C's output increased
  to about 600mW.

You can download the schematic is here.
Download PC Layouts: AF board,  RF board, VFO board, PA board. (comming soon)

prototype    The prototype transceiver.

top view    View of HF and AF boards.

pa board    View of the 500mW PA board.

vfo board   View of the VFO/BFO board.

vfo-hf-af    Another view of the HF and AF boards.

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Last Update: 19/11/2006