THE QRP LABS 20

Building The QCX 20M 5W CW Tranceiver
The Assembly Manual


Bags of parts to be inventoried.


Top of PCB (L), Bottom of PCB (R)
Notice SMT components installed at factory.

~~ Step 3.1~~

Inventory the parts.

The kit has been inventoried. No missing parts.

Each part was placed in #1 coin envelopes and labeled. To make
it easier to find when needed. There were several extra components

OK! LETS GET TO IT
NOTICE! the color coding in the manual
The part(s) being installed are "RED"
Those parts already installed are "GRAY"
The parts that have not been installed are "WHITE"

~~ Step 3.2~~

Install the 28 pin IC socket for IC2

(L) from the manual, (R) on the PCB
BE SURE to observe the proper orientation.

~~ Step 3.3~~

Install the DIP intergrated circuits IC3, IC5-10

(L) from the manual, (R) on the PCB
BE SURE to observe the proper orientation.

~~ Step 3.4~~

Install all 100nF (0.1uf,"104") capacitors
C2,C3,C6,C12,C29,C32,C34,C35,C36,C39,C40,C41,C48,C49,C50 and C52

(L) from the manual, (R) on the PCB

~~ Step 3.5~~

Install all 470nF ("474") capacitors
C11,C43,C44,C45 and C46

(L) from the manual, (R) on the PCB

~~ Step 3.6~~

Install all 1nF ("102") capacitors
C14,C16,C18,C23 and C33

(L) from the manual, (R) on the PCB

~~ Step 3.7~~

Install all 10nF ("103") capacitors
C4,C7,C10 and C42

(L) from the manual, (R) on the PCB

~~ Step 3.8~~

Install 47nF ("473") capacitors
C9 and C13

(L) from the manual, (R) on the PCB

~~ Step 3.9~~

Install 39nF ("393") capacitors
C17

(L) from the manual, (R) on the PCD

~~ Step 3.10~~

Install 2.2nF ("222") capacitors
C19 and C20

(L) from the manual, (R) on the PCB

~~ Step 3.11~~

Install 33nF ("333")and 3.3nF ("332") capacitors
C15 and C53 they are in parallel and make up 36nf

(L) from the manual, (R) on the PCB

~~ Step 3.12~~

Install capacitors C25 and C26
from the 20M Low Pass Filter Kit
they are 390pf ("391")

(L) from the manual, (R) on the PCB

~~ Step 3.13~~

Install capacitors C27 and C28
from the 20M Low Pass Filter Kit
they are 180pf ("181")

(L) from the manual, (R) on the PCB

~~ Step 3.14 ~~

Install 30pf ("300") capacitor
C30 the 20M band dependent capacitor

(L) from the manual, (R) on the PCD

~~ Step 3.15 ~~

Capacitors C5 and C8 not used on 20M

~~ Step 3.16 ~~

Install 1uf ("105") capacitor
C31 the 20M band dependent capacitor

(L) from the manual, (R) on the PCB

~~ Step 3.17 ~~

Install 1N4148 Diodes
D1,D2,D4 and D5. Observe orientation

(L) from the manual, (R) on the PCB

~~ Step 3.18 ~~

Install 1N5819 Diode
D3. Observe orientation

(L) from the manual, (R) on the PCB

~~ Step 3.19 ~~

Install 20Mhz Crystal

(L) from the manual, (R) on the PCB

~~ Step 3.20 ~~

Install 27Mhz Crystal


(L) from the manual, (R) on the PCB

~~ Step 3.21 ~~

Install all 15 10K resisters
R1,R2,R7,R10,R14,R34,R39,R40,R46,R49,R50,R51,R52,R57 and R58

(L) from the manual, (R) on the PCB

~~ Step 3.22~~

Install all 12 1K resisters
R3,R4,R25,R26,R37,R42,R45,R53,R54,R55,R62and R63

(L) from the manual, (R) on the PCB

~~ Step 3.23 ~~

Install all 11 3.3K resisters
R12,R13,R15,R16,R19,R20,R22,R23,R24,R44,R56 and R59

(L) from the manual, (R) on the PCB

~~ Step 3.24 ~~

Install all 4 100 ohm resisters
R5,R6,R8 and R9

(L) from the manual, (R) on the PCB

~~ Step 3.25 ~~

Install all 3 120K ohm resisters
R38,R43 and R60

(L) from the manual, (R) on the PCB

~~ Step 3.26 ~~

Install 2 33K ohm resisters
R28 and R29

(L) from the manual, (R) on the PCB

~~ Step 3.27 ~~

Install 2 47k ohm resisters
R30 and R31

(L) from the manual, (R) on the PCB

~~ Step 3.28 ~~

Install 2 36k ohm resisters
R32 and R33

(L) from the manual, (R) on the PCB

~~ Step 3.29 ~~

Install 270 ohm resisters at R48

(L) from the manual, (R) on the PCB

~~ Step 3.30 ~~

Install 470 ohm resisters at R41

(L) from the manual, (R) on the PCB

~~ Step 3.31 ~~

Install 3.9K ohm resisters at R61

(L) from the manual, (R) on the PCB

~~ Step 3.32 ~~

Install 4.3K ohm resisters at R18

(L) from the manual, (R) on the PCB

~~ Step 3.33 ~~

Install 5.1K ohm resisters at R11

(L) from the manual, (R) on the PCB

~~ Step 3.34 ~~

Install 7.5K ohm resisters at R21

(L) from the manual, (R) on the PCB

~~ Step 3.35 ~~

Install 750K ohm resisters at R48

(L) from the manual, (R) on the PCB

~~ Step 3.36 ~~

Install 100K ohm LCD Contract trimmer resister at R47

(L) from the manual, (R) on the PCB

~~ Step 3.37 ~~

Install 500 ohm multi-turn trimmer potentiometer at R27
Observe orientation

(L) from the manual, (R) on the PCB

~~ Step 3.38 ~~

Install 50k ohm multi-turn trimmer potentiometer at R17and R24
Observe orientation

(L) from the manual, (R) on the PCB

~~ Step 3.39 ~~

Install 2 100uh inductors at L5 and L6

(L) from the manual, (R) on the PCB

~~ Step 3.40 ~~

Install 6 10uf electrolytic capacitors C21,C22,C24,C37,C38 and C51
capacitors are polarised,Observe orientation

(L) from the manual, (R) on the PCB

~~ Step 3.41 ~~

Install 220uf (may be supply at 470uf) electrolytic capacitor at C47
capacitor is polarised, Observe orientation
because of component height install horizontally

(L) from the manual, (R) on the PCB

~~ Step 3.42 ~~

Install 30pf Trimmer capacitor C1

(L) from the manual, (R) on the PCB

~~ Step 3.43 ~~

Install Transistor Q6 MSP751

(L) from the manual, (R) on the PCB

~~ Step 3.44 ~~

Install Transistors BS170 at Q1,Q2,Q3, Q4,Q5 and Q7

(L) from the manual, (R) on the PCB

~~ Step 3.45 ~~

Install 2 X3 pin in-circuit programing header

(L) from the manual, (R) on the PCB

~~ Step 3.46 ~~

Install 4 pin GPS header

(L) from the manual, (R) on the PCB

~~ Step 3.47 ~~

Install 3 pin DVM/RF detector header

(L) from the manual, (R) on the PCB

~~ Step 3.48 ~~

Install 3 1-pin TEST POINTS

(L) from the manual, (R) on the PCB

~~ Step 3.49 ~~

Install power connector

(L) from the manual, (R) on the PCB

~~ Step 3.50 ~~

Install 7805 voltage regulator IC11

(L) from the manual, (R) on the PCB

~~ Step 3.51 ~~

Install pin headers for the LCD module

(L) from the manual, (R) on the PCB

~~ Step 3.52 ~~

Wind and Install toroid L4
using a T37-2 toroid wind 10 turns for 20M

(L) from the manual, (C) the toroid (R) on the PCB

~~ Step 3.53 ~~

Wind and Install toroid L4
using a T37-6 toroid wind 17 turns for 20M

(L) from the manual, (C) the toroid (R) on the PCB

~~ Step 3.54 ~~

Wind and Install toroids L1 and L3
using a T37-6 toroid wind 16 turns for 20M

(L) from the manual, (C) the toroids (R) on the PCB

~~ Step 3.55 ~~

Wind and Install transformer T1

(L) a drawing of T1 (R) a schematic of T1

(L) turns needed for 20m (R) how T1 should look mounted

(L) 1st attempt (R)2nd attempt
Now to try mounting T1, man it's a BOOGER

(L) transformer T1 is now mounted, (R) A close up view of T1
I found this to be an extremely tricky process.
~~ Step 3.56 ~~

Install RF output BNC connector

(L) from the manual, (R) on the PCB

~~ Step 3.57 ~~

Install 3.5mm stereo connectors

(L) from the manual, (R) on the PCB

~~ Step 3.58 ~~

Install buttons S2 and S3 (left and right buttons)

(L) from the manual, (R) on the PCB

~~ Step 3.59 ~~

Install rotary encoder

(L) from the manual, (R) on the PCB

~~ Step 3.60 ~~

Install MICROSWITCH

(L) from the manual, (R) on the PCB

~~ Step 3.61 ~~

Install gain control potentiometer R36

(L) from the manual, (R) on the PCB

~~ Step 3.62 ~~

Install four 12mm hex spacers at the LCD corners

(L) from the manual, (R) on the PCB

~~ Step 3.63 ~~

Install four 12mm hex spacers at the PCB corners

(L) from the manual, (R) on the PCB

~~ Step 3.64 ~~

Install the two knobs

~~ Step 3.65 ~~

Install 16-pin female connector on LCD module

~~ Step 3.66

Install microcontroller

~~ Step 3.67 ~~

Install LCD and four screws to bolt on LCD module

This QCX 20M TRANSCEIVER IS COMPLETE

~~ Step 3.70 ~~

Alignment and Calibration

Fused power supply built and power applied

Contrast ajusted.

Select band that transceiver was built for

In this case its twenty meters (14mhz)

Frequency selection made

14.020 MHZ

Peak BPF (band pass filter)

Adjust I-Q balance

adjust R27 for minimum

Adjustment of 90 degree audio phase shift

Phase LO, adjust R24 for minimum


Phase HI,adjust R17 for minimum

Following the adjustments of the trimmers the transceiver is ready for use.

>-=-<+>-=-<
QCX-20RX TEST
VFO"A" IN UPPER LEFT shows14,006.05
VFO 'B" IN LOWER LEFT show 14,030.00
"S" METER IN UPPER RIGHT
CW DECODER ON LOWER RIGHT

TX TESTED
On dummy load 16.73v on meter converts to 4watts output
successful CW contact made

QCX-20QCX MOUNTED