The BC547 80M SSB QRP Transceiver
An Easy To Build All Transistor Transceiver
a bit of a retro design, and uses easily obtained parts, no hard to
find or expensive ic's (no ic's at all).
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
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 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
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
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
All transistors used are BC547 & BC557. In the
prototype I used all BC547C types, but in the final version I used
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.
The prototype transceiver.
View of HF and AF boards.
View of the 500mW PA board.
View of the VFO/BFO board.
Another view of the HF and AF boards.
Last Update: 19/11/2006