Small Wonder Labs PSK-20 User manual

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 1
PSK-20 Transceiver
Board Kit Instructions
Please take a few moments to look over the sections entitled "First Things First" and "Building Instructions"
before you dive in. These sections contain information which is key to your success with this kit
TABLE OF CONTENTS:
First Things First..................................... 2
Materials ................................................... 3
Component Identification……………….. 4
Parts List ................................................... 5
Operational Desription ..................................6
Schematics ................................................. 8
Pictorial Drawing................................... 10
Building instructions , general......... 11
Grouped assy. Instr……. 12
"Hooking Up" ................................ 20
Alignment ................................................ 21
Troubleshooting the "PSK-20 " ............... 22
"Frequently Asked Questions"………………24

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 2
THE FINE PRINT:
There are lots of small parts in this kit. With many of
us getting older, this may prove troublesome. I highly
recommend a magnifying glass or close-up glasses to
check all solder joints and component codes.
THE OTHER FINE PRINT:
If you encounter conflicts between various sections of
this document, contact me for a resolution. The
following order of precedence applies:
• Schematic (most trustworthy)
• Parts list
• Pictorial
• grouped assembly text
• Everything else
TOOLS:
You'll need the following tools:
-Soldering iron- ~25W
- 60/40 solder, small diameter
-Diagonal cutters
-Needle-nose pliers
-Small slot screwdriver
-Wire-strippers (recommended)
-Tweezers (recommended)
TEST EQUIPMENT:
- Wattmeter (Radio Shack #21-534 / equiv.) ($30)
-Multimeter (recommended)
- Amateur transceiver (recommended)
PSK-20 Power Requirements .
The PSK-20 is designed to operate with a minimum
supply voltage of approximately 10V. A power supply
capable of delivering a minimum of 1 Amp at 12-14
Volts DC is recommended. Maximum recommended
supply voltage is 15VDC.
A low-cost supply suggestion: Jameco's #228822, 15V
regulated 'wall-wart'. This supply requires a plug
adapter, their #229155CL. They're at 800-831-4242.
Note: the less expensive unregulated 'wall-warts' will
not provide adequately filtered DC- don't waste your
money! 'Filtered' is not sufficient- you need to see
the word "Regulated' on the description.
FIRST THINGS FIRST - -Stuff worth knowing!
COLOR CODES:
Resistor color codes are given in the parts list.
Radio Shack's Color-Code Guide, #271-1210, or the
ARRL Handbook will help. If you're not sure, verify
the resistor values with a multimeter before installing.
For what it's worth, roughly 8% of the male
population is red/green color-blind. If you're one of
these, you should be verifying all resistors with a
multimeter before installing them.
The PSK-20 board is double-sided and all holes on
the board are plated-through. This means that you do
not need to solder on the top side of the board.
SOLDERING SKILLS
Hopefully this isn't your first experience with a
soldering iron. If it is, though, or this is your first
solid-state project, here are some tips to ensure your
success:
- Soldering Iron:
Use a small iron in the 25-watt class (such as a Radio
Shack #64-2070) and keep the tip clean. Use a
moistened sponge or paper towel to clean the tip
periodically as you work.
Apply only as much heat as is needed to get a good
joint. A small vise to hold the printed-circuit board
may make soldering easier.
Touch the soldering iron tip to the PC board trace and
the component lead simultaneously. Within a second
or two, apply solder and you'll see the solder flow onto
the junction. Withdraw the solder and then the
soldering iron.
Avoid the temptation to load solder onto the joint
until no more will fit! This is an invitation for trouble,
as solder bridges may form across the closer trace
separations. Here's what the correct and incorrect joint
treatments look like:

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 3
.
PLEASE READ THE SECTION BELOW BEFORE
REMOVING ANY PARTS FROM THE BOARD
Uh-oh! Sooner or later, you may need to remove a
part installed in the wrong location, or perhaps pull a
component for troubleshooting purposes.
Get yourself a roll of desoldering braid (Radio Shack
#64-2090B). Lay the end of the braid down on the
joint to be cleaned and press the soldering iron tip over
the braid. Within several seconds you'll see the braid
begin to wick up solder from the joint. Remove the
braid and reapply a new section as needed until the
joint is clean. It may be necessary to pull the
component out from the top side of the board while
heating the joint. Leave the iron tip on the board only
as long as necessary to do the job- the PC-board traces
will eventually delaminate (peel off) if overheated.
If that still doesn't do the job, it may be necessary to
cut the offending part off on the top side and pull the
remaining leads through with pliers. Contact me for
replacement parts if necessary.
If you need to remove a transistor, I'd highly
recommend sacrificing the part by snipping it off on
the top side of the board. The leads are best pulled out
singly to minimize the risk of lifting pads.
After removing a component from the board, the
through-hole will probably still be blocked with solder.
Use a dissecting needle or dental probe (explorer),
apply heat to the probe and the board trace
simultaneously until the tool pushes through. Lacking
either of these tools, a round wooden toothpick works
well also!
WINDING TOROIDS:
-Count as you go. Draw each turn snug against the
core to ensure a trim and tight winding
-Double-check the turns count when you're finished.
Use your fingernail or small screwdriver to "bump"
over each turn as you count- this is considerably easier
than counting by eye.
- Trim the excess wire off to about 1/4" and strip the
insulation off the ends with a wirestripping tool.
(Make sure the stripper is adjusted correctly for the
wire- it should cut the insulation cleanly but should not
nick the wire itself- try this out on a sample length of
toroid wire first.)
Counting the turns:
If the wire passes through the toroid center hole, it
counts as a turn. Here's an example:
REFERENCE DESIGNATORS:
Each component is uniquely identified with a
reference designator. Bypass capacitors are identified
as C101 and up. Reference designators are shown in
blue on the schematic pages.
C OMPONENT IDENTIFICATION :
• Resistors and RF chokes
This manual describes the color coding for all resistors
and RF chokes. Only the first three bands are
described, the fourth band is a tolerance code, typically
gold (=5%) and is not listed. All resistors are 1/4W 5%
carbon film types, RF chokes are also an axial (leads
out of each end) component but are notably larger.
GOOD
SOLDER FILLET IS CONCAVE AND 'WETS'
SMOOTHLY TO COMPONENT LEAD
BAD
SOLDER FILLET IS CONVEX OR DOES NOT
ADHERE TO COMPONENT LEAD
This toroid is wound with 8 turns
Turns must be uniformly distributed around
the circumference of the toroid.

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 4
• Capacitors:
These are disk capacitors (‘caps’):
Here's the general rule for disk cap nomenclature:
If 3 digits are printed on the capacitor, the first two are
significant figures and the third is a multiplier.
Examples:
'471' = 47 x 10
1 =
470 pF
'103' = 10 x 10
3 =
10,000 pF = .01 uF
Letter suffixes: J=5%, K=10%, M=20%.
Please: If you're not sure, please be sure to inspect
both sides of the caps before concluding we gave you
the wrong value!
These are monolithic caps:
These caps generally follow the same marking conventions
as for the disk caps.
The monolithic caps in this kit are provided in their
own poly bag. Capacitors are separated by value
within this bag and are ordered by capacitance value.
The capacitors in this assortment are identified by
shading on the parts list on the next page. Cut this bag
open when you're ready to proceed, and store the
groups of capacitors separately in marked envelopes or
small paper cups.
If these parts are supplied with a 0.1" (2.5mm) lead-
spacing for installation in a board hole-spacing of 0.2"
(5 mm), bend the wire leads gently to spread the
spacing . Avoid sharp bends right at the wire-lead exit
from the epoxy case; this may cause component
damage/failure.
These are electrolytic caps:
The black band on the left side of the cap bodies above
denotes the negative ( - ) side of the capacitor.
These are marked directly with the component value
and voltage rating. Note that you may find a higher-
than-specified voltage rating. It’s OK!
• Extra information on components
There's often extraneous information marked on
components. Examining a sample IC, I find
"MC1458P1 KKJK 8949". You care only about the
'1458' or other markings I've specified If I've specified
a capacitor '104' and you find the correct number of
parts, but marked "104M', for instance, those are
them!
You'll find the following items with your PSK-20 kit:
1- bag of parts, miscellaneous
1- antistatic bag (contains semiconductors)
1- poly bag- SMT inductors, diodes
1- poly bag (resistors/disk capacitors)
1- poly bag (monolithic capacitors)
1- printed circuit board
- (this manual)

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 5
PARTS LIST
Quantity Reference Designator Value Description Markings or Ident.
1 C29 4.7 pF Disk cap 4.7
11 C1, C5-C9,C19-C23 27 pF Disk cap 27
1 C38 4-20 pF Trim cap Red, 2 leads
1 C42 6-30 pF Trim cap Green, 2 leads
3 C13, C39,C40 47 pF Disk cap 47
4 C3, C28,C30,C41 100 pF Monolithic cap 101J
2 C32,C37 150 pF Monolithic cap 151J
2 C43,C44 180 pF Monolithic cap 181J
2 C34,C36 330 pF Monolithic cap 331
4 C2,C27,C31,C35 470 pF Monolithic cap 471
20 C4,10,11,C24-26,C101-105,
C107-113,C118,C119
.01 uF Disk cap 103
6 C12,16,33,C114,115,117 .1 uF Monolithic cap 104
2 C15,C17 1 uF Electrolytic cap 1 uF
1 C14 10 uF Electrolytic cap 10 uF
1 C18 47 uF Electrolytic cap 47 uF
2 C106,C116 220 uF Electrolytic cap 220 uF
7 D1-D4,D7,D8,D10 1N4148A Diode Glass body, on tape
3 D5,D6,D9 1N5236B Diode, 7.5V Zener In marked bag-strip
1 D11 1N4001 Diode 1N4001
1 D12 1N5818 Diode 1N5818
1 HS1 - - Heat sink, small Black metal, w/ fins
1 HS2 - - Heat sink, medium Black metal, w/ fins
2 J1,J2 - - 3.5mm audio jack 3 leads, rectangular
1 J3 - - Power jack, 2.1/5.5 mm 3 leads, rectangular
1 J4 - - BNC, w/ lockwasher, nut (Antenna jack)
1 L1 4.7 uH RF choke Ylw-Viol-Gold
3 L2,L5,L6 1.5 uH Slug-tuned inductor, 10 mm
1 L3 3.3 uH SMT inductor In marked bag-strip
1 L7 1 uH SMT inductor In marked bag-strip
1 L8 T37-2 Toroid, 11 turns #24 Red 'doughnut'
2 L9, L10 T37-6 Toroid, 15 turns #24 Yellow 'doughnut'
1 P1 - - DC Power Plug, 2.1/5.5mm Plug, black body
2 Q1,Q3 2N3906 Transistor, TO-92 pkg. Small, plastic body
2 Q2,Q4 2N7000 Transistor, TO-92 pkg. Small, plastic body
4 Q5,Q6,Q8,Q9 2N4401 Transistor, TO-92 pkg. Small, plastic body
1 Q7 MPSH10 Transistor, TO-92 pkg. Small, plastic body
1 Q10 2SC1970 Transistor, TO-220 pkg. Large, metal tab
1 Q11 2SC1971 Transistor, TO-220 pkg. Large, metal tab
5 - - - - IC socket, 8-pin DIP 8 leads
3 R40-R42 1.5 ohm Resistor, 1/4w 5% Brown-grn-gld-gld
4 R9,R33,R35,R38 6.8 ohm " Blue-grey-gld-gld
3 R25, R26,R39 51 ohm " Grn-brn-blk-gld
2 R2,R32 100 ohm " Brn-Blk-brown-gold
2 R30,R34 220 ohm " Red-red-brown-gld
8 R1,R3,R4,R11,R22-R24,49 470 ohm " Ylw-viol-brown-gld
1 R27 680 ohm " Blue-gry-brown-gld
5 R6, R29,R37,R45,R48 1K " Brown-blk-red-gld

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 6
Parts list (cont'd)
Quantity Reference Designator Value Description Markings or Ident.
2 R12,R15 2.2K " Red-red-red-gld
1 R36 3.3K " Orange-org-red-gold
5 R5,R7,R18,R21,R28 4.7K " Ylw-viol-red-gld
4 R10,R14,R16,R20 10K " Brn-blk-orange-gld
5 R19,R31,R44,R47,R50 22K " Red-red-orange-gld
2 R43,R46 47K " Ylw-viol-orange-gld
1 R13 100K Brown-blk-ylw-gold
1 R8 510K " Grn-brn-yellow-gld
1 R17 1M " Brn-blk-green-gld
1 T1 FT50-43 Toroid, 4 turns -see text Grey 'doughnut'
3 U1,U2,U7 SA612AN Integrated circuit 8 leads, plastic
2 U3,U4 LM1458 Integrated circuit 8 leads, plastic
1 U5 TUF-1 Mixer, metal can package 4 leads, in-line
1 U6 78L08 Integrated ckt, TO-92 pkg. Small, plastic body
1 U8 MAR-3SM Surface-mnt IC, preinstalled Tiny- 4 leads
1 W1 - - 2' (0.7m) power wire 2-conductor
9 Y1-Y5,Y7-Y10 9.00 MHz Crystal, series-load
1 Y6 5.0688
MHz
Crystal, 20-pF load
1 - - - - Printed-circuit board 'SWL 3/02'
1 - - - - Mica washer
1 - - - - #4-40 x 1/4" nylon screw
1 - - - - #4-40 x 1/4"steel screw
2 - - - - #4-40 nut
1 - - - - 3' (1m) #24 magnet wire
2 - - 4" (10cm) solid wire Color varies
Theory of Operation:
This transceiver is a single PC-board design measuring
4.6" x 5.27" (12 x 13.4 cm). It is functionally a
crystal-controlled SSB transceiver with slightly wider-
than-normal IF passband characteristics. It covers the
range of 14.070 to 14.074 Mhz.
Receiver Operation:
The receiver RF input (schematic point 'D') is
applied through a series-tuned resonant circuit
(C1/L1). Diodes D1-D4 limit during key-down and
thereby restrict the signal levels presented to the
receiver front-end during transmit. The double-diode
configuration raises the network's intercept point with
respect to W7EL's original configuration to improve
IMD immunity. The combination of C2,C3 and L2
are a tuned circuit network which matches the input
impedance (1.5K ohms) of mixer U1.
U1 is fed with a 5.07 Mhz Local Oscillator (LO)
signal and converts the incoming 14.07 Mhz received
signal to the 9.00 MHz Intermediate Frequency (IF).
This mixer has approximately 12 dB of conversion
gain. The transistor (Q1) following the mixer is
configured as an amplifier with another ~12 dB of
gain.
Y1-Y4 and associated capacitors are the IF filter.
This filter has a 3-dB bandwidth of approximately 3.5
Khz and loss of roughly 2 dB. Its output is terminated
by the combination of R5 (2.2K) and U2's input
resistance
Product detector U2 receives the 9 Mhz IF filter
output and multiplies (mixes) it with a ~ 9 Mhz LO
signal (from schematic point 'E'. This results in an
audio output at pin 5 of that IC. C13 provides rolloff of
the audio to reduce high-frequency 'hiss'. Op-amp U3
and associated components provide audio
amplification. This stage has a gain of approximately
100 (40 dB).

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 7
Because the active soundcard inputs are always
active, even during transmit, the receiver must be
'muted' during transmit. Without this feature, the
receiver output will be mixed back through the
soundcard (in parallel with the desired DSP-based
transmitter drive) and cause transmitted signal
distortion. MOSFET Q2 provides this function by
shorting the receiver output to ground during transmit.
T-R Switching:
T-R switching is controlled by dual op-amp U4 and
associated components. The first section, U4-A, is
configured as a peak detector with a gain of
approximately 20 (26 dB). Incoming audio from the
computer sound card causes the voltage at capacitor
C16 to charge upwards in voltage. When the voltage is
high enough, the op-amp section U4-B switches its
output level from 'high' (~12V) to 'low' (~0-2V). This
threshold corresponds to a power output slightly
above 1W PEP [for a properly-adjusted PSK-20.]
The 'low' voltage at U4, pin 7 causes DC current to
flow out of the base of Q3 (via R18) and turns on Q3.
This circuit provide 'Vsw' used to bias a number of
transmitter stages.
'Vsw' is at 0V during receive and switches to V+
(~12V) on transmit. This also turns on (unmutes) TX
audio FET Q4. It also turns on RX muting FET Q2.
Transmitter operation:
Audio from the computer soundcard is applied to
the transmitter via J2. Q4 is switched on during
transmit and allows soundcard audio to reach the
amplifier stage (Q5 and associated components). Note
that when Q4 is off during 'receive', DC bias is
removed from Q5 and it is also non-conducting. The
combination of Q4 and Q5 provide relatively high
attenuation (>60 dB) of the soundcard audio during
receive. This is necessary since the transmitter's
double-sideband (DSB) generator -U5- is running
continuously- an audio signal applied to that stage's
input would be plainly audible through the receiver.
This situation would lead to soundcard
feedback/distortion on receive without the presence of
this muting function.
Single-sideband filtering is performed by a second
filter comprising Y7-Y10 and related capacitors. After
passing through the transmit IF filter comprising Y7-
Y10 and related components, the signal has been
reduced to a 9 MHz SSB signal. Its output drives 2nd
mixer U7. This mixer is also driven by a signal from
the 5.07 MHz LO, Colpitts oscillator Q9 and
associated components.
The output of this mixer consists primarily of both
the sum (14.07 MHz) and difference (3.93 Mhz)
frequencies applied to the mixer. Q7 is an emitter
follower used to buffer the high-impedance output of
the mixer. U8 is a Monolithic Microwave IC (MMIC)
and provides approximately 12 dB of gain.
Because the output of mixer U7 has energy on a
number of frequencies, bandpass filtering is required to
clean up its spectrum. L5, L6 and associated capacitors
form this filter, with input and output impedances of
50 ohms.
Q10 and associated components are the
transmitter's driver stage. This stage is feedback-
controlled by R36 for good linearity and operates
class-A (always conducting). The output of this stage
is L-network matched via L7 and C33 to the Power
Amplifier (PA) base. D11 biases the PA base to the
threshold of conduction, necessary for linear operation.
The PA stage (Q11) features a bifilar transformer (T1)
at its collector. This provides a 1:4 impedance match,
transforming the PA collector impedance at rated
power to 50 ohms. L8-L10 and C34-C37 are a 7-
element low pass filter used to remove harmonic
content from the PA output waveform. The design
complies with current FCC requirements for spurious
emissions. All harmonics were down at least 40 dB.
The largest spurious output is down 50 dB.

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 8
.01
U2
1
2
3
8
5
6
6V
1K
.01
.01
.1 6
57
4 8
220
47 pF
510K
10 uF
470
2.2K
10K
.01
V+
6.8
4.7K
J1
AF Out
.01 Vr
E
V+
Vsw
9.00 MHz
Y1 Y2 Y3 Y4
C5-C9: 27 pF
470
470
100
U1
1
2
3
8
4
6
6V
470
.01
.01
B
V+
D
.01
100
470
4.7 uH
27 pF
Q2
C1
D1
D2 D3
D4
C2
C3
R1
D5
L2
L1
Q1
R2
R3
R4
R6
R7
R
R8
R10 R11
C101
C102
C4
C5
C6 C7 C8
C
C103
C104
C10
C11
D6
C12
C105
C106
R12
C13
C14
U3
R50
22K
14 Mhz PSK31 Transceiver
D. Benson, K1SWL 1 27 2004 p.1 of 2
Vsw
Vr
V+ .01
5
6
7
8 4
.1
3
21
10K
100K
10K
2N3 06
.01
4.7K
V+
1M
V+
1 uF
F
- +
U4-A
U4-B
Q3
C15
C16
R13
R17
R16 R15
R14
2.2K D7
D8
C107
R18
R1
22K
C108
1.5 uH
LM1458
LM1458
R5
4.7K

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 9
14 Mhz PSK31 Transceiver
D. Benson, K1SWL 1 27 2004 p.2 of 2
A
E
B
A
D
J2
Y7 Y8 Y Y10
Y5 Y6
Q
TP1
L5 L6 D11
T1
J3
Vr
Vr
Vr
V+
Vr
Vsw
Vsw
Vsw
ANT.
150
330 470 330
220 uF
.1
.1
150
1.5 (3 pl)
.1
51
6.8
.1
6.8
3.3K
1K
1.5 uH
470
4.7
4-20 22K
47K
47 (2 pl)
1K
3.3 uH
100
.01
78L08
IN
5.068
.01
1 uF 10K
4
.
7K 470
47 uF
2
3
1
1 uH
(XMTR AF In)
4
51
680
Y7-Y10: .000 Mhz
C1 -C23: 27 pF .01
1 2
3
8
5
6
.01
6.0V
1K
.01
100
22K
220
.01
220
6.8 .01
.01
.01
1K
.01
47K
MHz
.00
MHz
6-30
22K
MAR-3SM
V+
LINE OUT
Vsw
(8V)
470
Vr
470
51
470
100 100
180 (2 pl)
F
470
Vsw
C10
C17 R20
Q4
R21
R22
R23 R24
R25
Q5
Q6
C18 R26
R27
U5
R2 R30
R31
R32
R33
R34
C110
C111 C112
C113
C1
C20 C21 C22
C23
C24
C25
C26
D
D10
D12
U6
U7
U8
Q7
Q8
Q10
Q11
L3
'L4'
L7
L8 L L10
C27
C28
C2
C30
C31
C32
C33
C34 C35 C36 C37
C38
C3
C40
C41
C42
C43
C44
R35
R36
R37
R38
R3
R40-R42
R43
R44
R45
R46
R47
R48
R4
C114
C115
C116
C117
C118
C11
J4
Install
jumper
R28
4.7K
1.5 uH

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 10
470
51
D12
C1
L6
BNC
MICR. LINE
OUT
T1
L10
D10
TP1
330
470
100
1.5
.1
PWR.
J1 J2
100
.1
C29
4.7
R12
R11
2.2K
470
C14
- +
10 uF
.1
C33
6.8
51
U3
C13
R8
47 pF
510K - +
C106
220 uF
U2
R9
1K
6.8
.01 C104
R6
C12
.1 uF
R7 4.7K
U4
C15
C107
.01
10K
2.2K
MCL
TUF-1
Q2 R1410K
- +
- +
C17
1 uF 1 uF
.01
C109
Q4
Q5 Q6 U5
4.7K
- +
47 uF
10K 470
Y7
680
C20
C21
27 27 27 27
Y8 Y9
Y1
Y2
Y3
Y4 27
27
27
27
U7
.01
470
C111
C108
+ -
27
D1
D4
L1
4.7 uH
220 uF
C116
U6
Q3
Y5
C42 Y6
C118
.01
Q8
R18
D7 4.7K
L3
R44
C39
C40
47
22K
100
1K
47K
R43
R45
U8
.01
100 220
1K
R31
220
22K
.01
C112
Q11
180
Q9
1K
C24
.01
.01
R40
R41
R42
1N4001
R33
6.8
3.3K
1K
R37
.01
C34
C35
C36
C37
470
330
J4
J3
150
L9
L8
.01
C101
C2
C3
470
100
U1
L2
D6
C11
.01
C9
C8 C7
C6
27
C5
R5
C103
R16
R19
22K
2N7000
2N 4401
2N 4401
R21
R20
R22
C18
R24
470
51
R25
R23
470
Y10
R26
R27
27
C19
C22
C23
C26
C28
R34
R29
Q7
.01
C25
C27
R32
.01
R30
D9
.01
R28
C110
180
C43 C44
R17
R13
D8
100K
1M
C16
.1 uF
R15
2N7000
2N3906
R10
C10
C105
.01
.01
10K
C41
47
C38
L4
R3
22K 47K
R47 R46
R4
470
Q1
.01
C119
R2
100
SA602
SA602
LM
1458
LM 1458
R1
1K
D5
.01
C4
C32
150
R39
6.8
R48
R49
470
C117
C102
.01
C30 C31 D11
C115
R38
C113
R36
Q10
L5
R35
C114
.1
L7
1N5818
5.068
3.3 uH
1 uH
1/28/04
4.7K
4
.
7K
R50 22K
SA602

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 11
Building instructions:
All parts installed on the PC board should be fully
seated unless otherwise noted in the assembly text..
Static-sensitive Components:
Components noted in bold in the assembly text are
static-sensitive. The following general precautions
apply:
• Keep these parts in the antistatic bag until you're
ready to install them and handle them no more
than necessary.
• Ideally, you've got a grounded-tip iron, but if not-
After the part is installed on the board and before
soldering, touch the iron tip to shack ground (if
available) or to a PC-board ground point.
• Avoid placing these components on paper
• Diode Installation:
Some of the diodes are bent for "upright" or
'hairpin' installation on the board. Installation polarity
is as shown below. Be sure to note the orientation of
the circle on the pictorial illustration and install the
diode to match this orientation. The banded
(cathode) end of the diode is at the top. For diodes
which are installed 'lying down', match the banded end
to that shown on the silkscreen and pictorial
illustration.
Pictorial
Diode-
Schematic
Banded end
Is cathode
Pictorial or
Silkscreen
outline
• Resistor installation:
Many resistors are likewise installed in 'hairpin'
fashion. As with the diodes, try to match the mounting
orientation shown on the drawing. (If mounted as
shown you've got better troubleshooting access to
circuit points from the top side of the board.)
Orientation of color bands on resistors and other
nonpolar devices is not critical.
• Installing IC sockets:
The "notch" or dot at one end should be oriented as
shown in the pictorial drawings. Doublecheck
orientation before soldering. A suggestion- solder
down two opposite corners of each socket, and then go
back and press a fingertip on the socket from
underneath while reheating both connections in turn.
You may then solder the remaining pads. This
precaution ensures that the socket is well-seated on the
PC board.
Recommended Assembly sequence:
I've specified the sequence detailed in the pages
which follow, but there's nothing sacred about the
order in which the board is populated. Some parts are
best installed in a particular order, as noted within each
group's instructions.
Directions for winding toroids are found within each
group's assembly instructions.
Stuff only a few parts at a time (3-4 pieces). If you try
to add too many parts at once between soldering
operations, you may lose track and wind up with
missing solder joints! Once you've stuffed the parts on
the board, bend the protruding leads slightly outward
to keep them in place while the board is inverted for
soldering.
'The Real Men's Corner:'
This is for the folks who don't read instructions- you
know who you are! Be aware of the following:
Crystals and mixer U5 should be stood slightly
(0.5 to 1mm) above the printed-circuit board to
prevent shorts from case to ground.
Do not omit the mica washer from under the PA
transistor (Q11)- it's there for a reason!

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 12
-ASSEMBLY INSTRUCTIONS:
The following component is pre-mounted on the
board: U8
Mount all components on the silkscreened side of
the board. Solder components into place and trim
leads after installation unless otherwise noted .
You may find it convenient to install 3-4 parts
at a time between soldering operations.
Group 1 Assembly:
Group 1 assembly installs the DC power circuitry.
Install the DC power jack (black, 3 tabs) at J3.
Note: there will be 'play' in the orientation of
this part due to the slot widths - make sure it
is carefully aligned square to the board edges
before soldering all three tabs.
Install diode D12 (1N5818) immediately
below J3. Match the installation orientation as
shown on the silkscreen.
Install electrolytic capacitor C116 (220 UF).
Observe the polarity marking on the device-
the dark bar down one side of the part denotes
the negative lead. Note that the longer of the
two capacitor leads is (+).
Assemble power cable using the 2' length of
black twin-conductor wire. (unthread and
remove the plastic shroud. The wire with the
white-striped insulation is considered
'positive' and connects to the center conductor
of the power plug. Once both leads are
soldered, install the plastic shroud. Note: not
to worry- the PSK-20 is reverse-polarity
protected by D12.
D12
PWR.
+ -
220 uF
C116
J3
(pads unused)
1N5818
Group 2 Assembly:
(Group 2 assembly installs the Transmit/Receive
switching circuitry).
Y10
(ref. only)
U4
C15
C107
.01
10K
2.2K
R1410K
- +
1 uF
.01
C109
C108
U6
Q3
C118
.01
R18
D7 4.7K
R16
R19
22K
.01
R17
R13
D8
100K
1M
C16
.1 uF
R15
2N3906
LM
1458
Install an 8-pin IC socket at U4. Match the
installation polarity as shown on the
silkscreen and pictorial drawing. Caution:
before soldering, make sure that all 8
socket leads protrude through the board.
Install .01 uF ('103') disk capacitors at C107,
C108, C109 and C118.
Install resistors R14 and R16 (10K,
brn/blk/org).
Install resistor R15 (2.2K, red/red/red).
Install 1N4148 diodes D7 and D8. Match the
installation polarity as shown on the
silkscreen and pictorial drawing..
Install resistor R17 (1M, brown-blk-green)
Install resistor R19 (22K, red-red-orange)
Install resistor R13 (100K, brn-blk-yellow)
Install resistor R18 (4.7K, ylw-violet-red)
Install electrolytic capacitor C15 (1 uF).
Match the installation polarity as shown on
the silkscreen and pictorial drawing..
Install monolithic capacitor C16 (.1 uF)
('104')

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 13
Install a 2N3906 plastic transistor at Q3.
Match the installation polarity as shown on
the silkscreen and pictorial drawing..
Install the 78L08 3-pin regulator at U6.
Match the installation polarity as shown on
the silkscreen and pictorial drawing..
Install a 3.5 mm audio jack at 'J2' near the
upper left corner of the board.
Install an LM1458 IC in the U4 socket. You
may wish to press the two rows of ICs gently
together (I use a tabletop surface) to ease
installation. Make sure that all pins seat
firmly in the IC socket.
Group 3 Assembly:
Group 3 assembly installs the 9 Mhz and 5.07 Mhz
local oscillators.
Install surface-mount inductor L3 (3.3 uH,
from bag strip). Note: the inductor itself is
inside a black plastic carrier. Pre-tin the
inductor pads on the PC board sparingly
with solder before installing the part. Place
this component on the two pad locations and
restrain carefully in place with tweezers. Tack
one end down with the soldering iron, solder
the other end sparingly, and retouch the end
originally tacked down. Good component
alignment is important to ensure that there
are no short-circuits- check your work
carefully for solder bridges.
Y5
C42 Y6
5.068
Q8
L3
R44
C39
C40
47
22K
100
1K
47K
R43
R45
180
Q9
1K
C24
.01
180
C43 C44
C41
47
C38
L4
22K 47K
R47 R46
.01
C119
R48
R49
470
9.00
3.3 uH
Install trimmer capacitor C38 (RED). Be sure
to orient the 'flat' side of the capacitor body as
shown on the pictorial and silkscreen.
Install trimmer capacitor C42 (GREEN). Be
sure to orient the 'flat' side of the capacitor
body as shown on the pictorial and silkscreen.
Install one of the 9.00 Mhz crystals at Y5.
Install this component slightly above the
board (0.5 to 1 mm) to prevent the case from
shorting to board traces. This is best
accomplished by installing and soldering the
crystal in place and then retouching the
connection while pulling gently on the
component to lift it slightly.
Install capacitor C41 (100 pF monolithic).
Install capacitors C39 and C40 (47 pF disk).
Install resistors R45,R48 (1K- brn-blk-red).
Note: R48 is not on board silkscreen.
Install resistors R43,R46 (47K-ylw-viol-org).
Install resistors R44,R47 (22K-red-red-org).
Install transistors Q8 and Q9 (2N4401, from
antistatic bag). Match the orientation of the
flat side of the components to that of the
silkscreen.
Install the single 5.068 Mhz crystal at Y6.
Provide height clearance as noted previously
for Y5 for this and all remaining crystal
installations.
Using a length of leftover wire lead from a
resistor, install a short wire jumper at the two
holes identified on the printed-circuit board as
'L4'.
Install R49 (470 ohm, yellow/violet/brown).
Install C43 and C44 (180 pF monolithic
caps).
Install C24 and C119 (.01 uF disk caps).

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 14
Group 4 Assembly:
Group 4 assembly installs the receiver AF amp,
product detector and crystal filter
MICR.
J1
R12
R11
2 . 2K
470
C14
- +
10 uF
U3
C13
R8
47 pF
510K - +
C106
220 uF
U2
R9
1K
6.8
.01 C104
R6
C12
.1 uF
R7
4 . 7K
Q2
Y1
Y2
Y3
Y4 27
27
27
27
4 . 7K
.01
D6
C11
.01
C9
C8
C7
C6
27
C5
R5
C103
2N7000
R10
C10
C105
.01
.01
10K
SA612
LM 1458
R50 22K
Install 8-pin IC sockets at U2 and U3. Match
the installation polarity as shown on the
silkscreen and pictorial drawing. Caution:
before soldering, make sure that all 8
socket leads protrude through the board.
Install resistor R12 (2.2K, red/red/red).
Install resistor R5 (4.7K, yellow/violet/red)
Install resistor R11 (470 ohm, ylw-viol-
brown).
Install resistor R8 (510K, grn-brn-yellow).
Install disk capacitor C13 (47 pF).
Install audio jack J1 at the upper left corner
of the board.
Install electrolytic capacitor C14 (10 uF).
Match the installation polarity as shown on
the silkscreen and pictorial drawing.
Install resistor R7 (4.7K, ylw/viol/red).
Install resistor R9 (6.8 ohm, blue/grey/gld).
Install .01 uF ('103') disk capacitors at C10,
C11,C103,C104 and C105.
Install electrolytic capacitor C106 (220 uF).
Match the installation polarity as shown on
the silkscreen and pictorial drawing.
Install a .1 uF monolithic capacitor ('104') at
C12.
Install resistor R10 (10K, brn/blk/org).
Install a 7.5V Zener diode (from bag strip) at
D6. Match the installation polarity as shown
on the silkscreen and pictorial drawing.
Install resistor R6 (1K, brn/blk/red).
Install resistor R50 (22K, red/red/orange).
Install disk capacitors C5-C9 (27 pF).
Install 9.00 Mhz crystals Y1-Y4.
Install jumper wires from the unlabeled single
holes to the left of Y1 and to the right sides of
Y2 and Y4. [Place the board on the
workbench surface and stand a resistor
upright in these holes. Solder on the top side
of the board and cut the lead to a length of
~1/8" (4mm).] Save the resistors for later use.
Bend the free end of each wire over to the
nearest crystal and solder each wire to the
crystal can. [The crystal cans are tinned and
will accept solder readily. Use no more heat
than necessary to ensure a good connection.]
Install a 2N7000 transistor at Q2. This part
is static-sensitive. Match the installation
polarity as shown on the silkscreen and
pictorial drawing.
Install a LM1458 IC from the antistatic
envelope) at U3. Match the installation
polarity as shown on the silkscreen and
pictorial drawing.
Install an SA612 IC from the antistatic
envelope) at U2. Match the installation
polarity as shown on the silkscreen and
pictorial drawing.

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 15
Group 5 Assembly:
Group 5 assembly installs the receiver 'front end'. The
receiver portion of the PSK-20 will be functional upon
completion of this group.
C1
BNC
L10
330
470
27
D1
D4
L1
4 . 7 uH
C34
C35
C36
C37
470
330
J4
150
L9
L8
.01
C101
C2
C3
470
100
U1
L2
R3 R4
Q1
R2
100
SA612
R1
470
D5
.01
C4
C102
.01
470
Install 1N4148 diodes at D1, D2, D3 and D4.
Match the installation polarity as shown on the
silkscreen and pictorial drawing.
Install C1 (27 pF disk capacitor)
Install a 4.7 RF choke (yellow/violet/gold) at
L1.
Note: the monolithic capacitors below are
somewhat fragile. If supplied with a 0.1"
lead spacing, but installed on pads with a
0.2" lead spacing, proceed as follows: Grasp
the capacitor body between thumb and
forefinger. Spread the wire leads apart
outward, taking care not to bend the leads
right at the capacitor body. The wire leads
may then be re-bent a few mm away from the
capacitor body to re-form them at the correct
parallel spacing.
Install a 470 pF ('471') monolithic capacitor at
C2.
Install a 100 pF ('101') monolithic cap at C3.
Install 330 pF ('331') monolithic capacitors at
C34 and C36.
Install a 150 pF ('151') monolithic cap at C37.
Install a 470 pF ('471') monolithic capacitor
at C35.
Install a slug tuned inductor (metal can) at L2.
Install a .01 uF ('103') disk capacitors at
C4,C101 and C102..
Install a 7.5V Zener diode (from bag strip) at
D5. Match the installation polarity as shown
on the silkscreen and pictorial drawing.
Install resistor R1 (470 ohm, ylw/violet/brn).
Install an 8-pin IC socket at U1. Match the
installation polarity as shown on the
silkscreen and pictorial drawing. Caution:
before soldering, make sure that all 8
socket leads protrude through the board.
Install resistor R2 (100 ohms,
brn/black/brown).
Install resistors R3 and R4 (470 ohm,
ylw/violet/brown).
Install a 2N3906 transistor at Q1. Match the
installation polarity as shown on the
silkscreen and pictorial drawing.
Install an SA612/SA602 IC at U1. Match the
installation polarity as shown on the
silkscreen and pictorial drawing.
L8, L9, L10 Winding Instructions:
Using an 8" (20 cm) length of magnet wire,
wind 11 turns on one of the 0.37" (1 cm)
diameter red toroids. After passing the wire
through the center hole each time, pull it snug
against the toroid as you proceed. Make sure
that each turn lays flat on the core- 'crossed' or
scramble-wound turns must be avoided.

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 16
Doublecheck the turns count, adjust the
spacing between turns for a uniform
appearance. Review the toroid sketch on
page 3 carefully. Mis-counting the turns is
a common source of difficulty for newer
builders.
Trim the excess wire ends to a length of ~3/8"
(1 cm). Each lead-end must be gently scraped
with a sharp knife or hobby knife blade to
remove the enamel insulation. Do not omit
this step, and do not count on your
soldering iron to melt the enamel.
Install this prepared toroid at 'L8'.
Using an 10" (25 cm) length of magnet wire,
wind 15 turns of wire on a T37-6 (yellow)
toroidal core. Prepare the toroid for
installation in the manner described above.
Install this prepared toroid at 'L9'.
Using an 10" (25 cm) length of magnet wire,
wind 15 turns of wire on the remaining T37-6
(yellow) toroidal core. Prepare the toroid for
installation in the manner described earlier..
Install this prepared toroid at 'L10'.
Install the BNC connector at J4. Solder all
pins.
* *
Group 6 Assembly:
Group 6 assembly installs the audio switch and
transmit first mixer.
51
MCL TUF-1
- +
C17
1 uF
Q4
Q5 Q6 U5
4 . 7K
- +
47 uF
10K
470
680
2N7000
2N
4401
2N
4401
R21
R20
R22
C18
R24
470
51
R25
R23
470
R26
R27
Install a 1 uF electrolytic capacitor at C17.
Match the installation polarity as shown on
the silkscreen and pictorial drawing.
Install resistor R20 (10K, brn/black/org).
Install resistors R22,R23 and R24 (470 ohm,
ylw/violet/brn).
Install resistor R21 (4.7K, yellow/violet/red).
Install resistor R25 ((51 ohm,
grn/brown/black).
Install resistor R27 (680 ohm,
blue/grey/brown).
Install resistor R26 (51 ohm, grn/brn/black).
Install Q4 (2N7000- from antistatic bag).
Match the orientation of the flat side of the
component to that of the silkscreen. This part
is static-sensitive.
Install Q5 and Q6 (2N4401- from antistatic
bag). Match the orientation of the flat side of
the components to that of the silkscreen
Install Mixer U5 (MCL TUF-1), from
antistatic bag). Be sure that the part
labeling is oriented as shown on the figure
on this page and that the part correctly
overlaps the silkscreened outline on the
board.
Caution: This component should be spaced
slightly above the board. Solder only 1 of
the 4 pins into place initially. Adjust
component spacing above the board while
briefly re-heating this connection, then
solder the remaining connections.
Install a 47 uF electrolytic capacitor at C18.
Match the installation polarity as shown on
the silkscreen and pictorial drawing.
* *

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 17
Group 7 Assembly:
Group 7 assembly installs the transmitter IF filter and
second mixer stages.
Y7
C20
C21
27 27 27 27
Y8 Y9
U7
C111
U8
.01
100 220
1K
R31
220
22K
.01
C112
.01
.01
Y10
27
C19
C22
C23
C26
R34
R29
Q7
.01
C25
R32
.01
R30
D9
4 . 7K
R28
C110
C113
R33
6.8
Install C19 through C23 (27 pF disk caps).
Install the remaining four 9.00 MHz crystals
at Y7-Y10. Add grounding wires (see p.14).
Install crystal ground leads to the left of Y7
and below Y8, Y9 and Y10 following the
procedure detailed earlier (group 4).
Install an 8-pin IC socket at U7. Match the
installation polarity as shown on the
silkscreen and pictorial drawing. Caution:
before soldering, make sure that all 8
socket leads protrude through the board.
Install R29 (1K, brown/blk/red).
Install D9 (7.5V Zener- from bag strip).
Observe the installation polarity as shown on
the silkscreen.
Install .01 uF ('103') disk capacitors at C25,
C26, C110, C111, C112 and C113
Install R28 (4.7K ohms, yellow/violet/red).
Install R30 and R34 (220 ohms,
red/red/brown).
Install R31 (22K, red/red/orange).
Install R32 (100 ohm, brown/blk/brown).
Install R33 (6.8 ohm, blue/grey/gold).
Install Q7 (MPSH10, from antistatic bag).
Match the orientation of the flat side of the
component to that of the silkscreen.
* *
Group 8 Assembly:
Group 8 assembly installs the transmitter bandpass
filter and driver stages.
L6
D10
TP1
470
100
180
.1
C29
4 . 7
6.8
51
220
1N4001
6.8
3.3K
1K
680
C28
R34
C27
C32
150
R39
C30 C31 D11
C115
R38
R36
Q10
L5
C114
.1
L7
R35
R37
Install L7 (1 uH SMT inductor, from the bag
strip.
Install C27 and C31 (470 pF monolithic caps,
'471').
Install C28 and C30 (100 pF monolithic caps,
'101').
Install C29 (4.7 pF disk capacitor).
Install C32 (150 pF monolithic cap, '151').
Install L5 and L6 (remaining two metal-can
tunable inductors)
Install R37 (1K, brown/blk/red).
Install R36 (3.3K, orange/org/red).
Install R35 and R38 (6.8Ω, blue/gry/gold).
Install R39 (51Ω, green/brn/black).

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 18
Install C114 and C115 (.1 uF monolithic cap,
'104') Note: C115 not labeled on silkscreen.
Install D10 (1N4148). Match the orientation
of the banded end of the diode with that of the
silkscreen and pictorial.
Install D11 (1N4001, power diode). Observe
the installation polarity as shown on the
silkscreen and pictorial.
Install Q10 (2SC1970, from antistatic bag).
Observe the component's tab orientation as
shown on the silkscreen. The metal tab is to
the rear; the lettering faces the front of the
board.
Install the smaller heatsink on the 2SC1970
using a metal screw and nut. Use the heat-
sink orientation (i.e., 'hole-up') which results
in the lower height above the board when
installed.
Tighten the hardware.
Caution: Ensure that R39 's wire lead is
not touching the heat sink.
* *
Group 9 Assembly:
Group 9 assembly installs the transmitter final
amplifier.
T1
1.5
.1
C117
.1
C33
Q11
R40 R41
R42
Install C33 and C117 (.1 uF monolithic
capacitors, '104').
T1 Winding Instructions:
Using the two 4" (10cm) lengths of solid wire,
wrap this wire-pair snugly around the toroid
for one complete turn. It should look like
this:
Proceed to thread the wire pair through the
hole again and draw it snug . Repeat this
threading operation twice more (a total of 4
wire-pair turns through the hole in all).
Caution:
The wires must not cross over each other
as they are laid down on the core (i.e.,
there are no 'twists' built into the wire. If
(color 1) is on the leading edge in the
direction you're winding, it must continue
on the leading edge for all 4 turns.
'Clockwise' and 'counterclockwise' winding
senses are non-critical- either one is fine.
Here's what the result looks like:
Note the way the color-pairs are arranged as
they proceed around the core.
As you look through the toroid hole (as
shown above, confirm that the 2 (first color)
leads protruding are on the left and the 2
(other color) are on the right.
Cut the protruding leads to a length of 1/2",
strip these with the wirestripping tool and
install at T1. Doublecheck the insulation
colors before soldering this component down.

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 19
(Assuming your wires are red and black, the red leads
go to the two 'upper' T1 mounting-holes and the black
leads go to the 'lower ' T1 mounting-holes. Or the
reverse- it doesn't matter. Your wire colors may vary.
T1 Q11
Install R40, R41 and R42 (1.5 ohms,
brown/green/gold).
Using a small screwdriver blade (or 8-10d
common nail) as a 'form', bend the 3 leads of
the 2SC1971 transistor downward at a 90°
angle as shown, immediately.outboard of the
wide portion of the leads. Take care to
ensure the resulting bent leads are
uniformly distant from the transistor body.
Cradle the 2SC1971 within the large heat sink
so that the hole in the transistor tab lines up
with that of the heatsink's hole.
'Sandwich' the mica washer between the
transistor and the heat sink so that all three
layers' holes line up.
Insert the nylon 4-40 machine screw
downward through the aligned holes in this
'sandwich'.
Use a fingertip to secure the nylon screw in
place, place this assembly on the board, insert
Q11's three leads into the corresponding
holes in the board. (Do not solder yet.) Secure
in place with a steel nut on the underside of
the board. . Make sure that the heat sink is
aligned parallel with the board before
tightening the nut. Tighten cautiously- the
nylon screw threads will strip at the torque
typically used for steel hardware. Solder
Q11's leads into place.
Caution: do not substitute a metallic screw here!
That's it- board assembly is complete!
CLEAN UP YOUR ACT! Before you proceed to
checkout, grab some cotton swabs and use acetone
(nail polish remover) or isopropyl alcohol to remove
solder flux from the underside of the PC board. The
result is a much cleaner appearance once you've
completed this step. Use acetone cautiously on the top
side of the boards- some of the plastic compenents
may be softened by contact with it.

Small Wonder Labs PSK-20 Transceiver Kit 8/31/04 20
Hooking Up:
The figure below shows the interconnect between
the PSK-20 board and the outside world (more on
alignment later)
Before the "Smoke Test":
Inspect your work to ensure there are no solder
bridges or unsoldered joints. Check to see that the ICs
are mounted in their proper orientations, or install them
if you haven't already done so (see p.10 for placement).
PSK-20 Mechanical Details
The board itself may be mounted in an enclosure at
the board's four corners, using #4 machine screw
hardware. #4 spacers should be used to separate the
PC board from the enclosure by 3/16" or more. ( #4
hex nuts are an acceptable substitute for spacers.)
Enclosures may be found in a variety of styles.
Radio Shack offers several types of metallic
enclosures. I'd especially recommend Hosfelt
Electronics, Inc., who carry enclosures offered by a
number of companies. There's no minimum order,
and they can be reached at [800] 524-6464 for a
catalog. Ten-Tec also offers a complete line of
enclosures, and they support small orders as well! Call
[800] 231-8842 for a free brochure.
The enclosure option for this transceiver is a
black/ grey extrusion enclosure with a companion
custom-punched end panel. The board size is
tailored to fit the enclosure side-rail slots and the
custom panel fastens to the BNC connector for
mechanical integrity. Information on this
enclosure may be found at:
http://smallwonderlabs.com
under 'PSK31'.
COMPUTER
MICR. IN
LINE or SPKR
OUT 'AF IN'
J2
J1 'AF OUT'
J4
'PWR'
'ANT.'
COAX, 50 OHM
(TO TUNER/SWR BRIDGE
OR ANTENNA)
DC POWER
12-15V @1A min
J3 center pin positive
Soundcard
Interface
PSK-20
1
1
CABLE DESCRIPTION:
1
3.5mm stereo (3-cond)
to 3.5mm stereo (3-cond)
Radio Shack # 42-2387
(2 required)
J3