QRP Labs QDX User instructions

QDX
QDX: QRP Labs Digital Xcvr (transceiver)
Assembly, design and operating manual
 1


 
  
! "
#
$% # 
&$' $
(! 
'!)*+,(
- .*'
"!# ## )
/  )$
)0!1  (
/   2 *'
%)3
$
1!0### 
(#$'4 $
',#(
,# '
$  $
$5$
$67 $(
$5% 8 $'
$$5  9 0 %
$50 % #2
$(:5# 
$')0 #:# 2
$-  +
$"35;02 $
$3$: $-7#<565'
$+*  .-
$ .= -
$+:!%:#!0# 2(-
$$50 %#)0!1 ("
$>### '-
1 0<##-
(* ## -
(!+ -
(3  ## -$
(3?  ## -$
($+2 -
( 20#-"
((120#"
('# "
(-+*"
(")2"-
(1
(<#20
 2

(3?  
'!.
' #
'* #
'!0###
'$,#% 
'<0 ## $
- 
"  4 
1 Introduction
The QDX is a high performance, four-band 5W Digital modes transceiver with CAT control and
built-in SB sound card. QRP Labs presents QDX, a digital transceiver with a ratio of performance
to price not available until now.
•Four band 80, 40, 30 and 20m; 5 W from 9 – 10V supply
•Clean single signal output (zero residual carrier, zero unwanted sideband)
•Solid state PIN-diode switched Low Pass Filters and solid state Band Pass Filters
•Solid state transmit/receive switching
•High performance embedded-SDR SSB receiver using 110dB 24-bit stereo ADC chip
•Built-in SB sound card: 48ksps 24-bit stereo
•Built in SB Virtual COM port serial for CAT control
•Si5351A Synthesized local oscillator with better than 0.001Hz resolution and high precision
25MHz TCXO reference as standard
•Built-in signal generator
•Built-in suite of configuration and analysis tools
•Lifetime free firmware upgrades with QRP Labs Firmware pdate (QF ) bootloader for
easy firmware update on any OS with no extra software, or drivers, or programming
hardware
•All SMD components pre-installed by factory, only through-hole component soldering by the
kit constructor
•Receive current: 100mA; Transmit current 1.0 – 1.1A (9V supply, 5W output)
•Only three connectors: SB (audio and serial for CAT), Power and RF
•Optional smart aluminium extruded enclosure measuring just 89 x 63 x 25mm
No test equipment is required to build, align and operate this digi modes transceiver. There are no
alignment tasks.
We hope you enjoy building and operating this kit! Please read this manual carefully, and follow
the instructions step by step in the recommended order. Later in the manual the circuit design is
described in detail and we recommend reading and understanding this section too, to get the
maximum enjoyment and education from your new radio.
Typical performance measurements are shown in the measurements section. The operation
section will get you started with QDX and your WSJT-X or other digi modes software in minutes.
PLEASE READ THE BASIC ASSEMBLY AND USE INSTRUCTIONS IN
THIS MANUAL VERY CAREFULLY BEFORE APPLYING POWER TO
THE BOARD!
 3

IMPORTANT!
QDX produces 5 W power output from a supply voltage of 9V or a little over. At 12 V QDX could
be producing 8 W power output which is likely to cause over-heating and perhaps failure of the
BS170 final transistors.
Operation of QDX at more than 6W power output is NOT RECOMMENDED
If you wish to operate using a 12 V supply, you may use a two turn secondary winding on the
output transformer T1, so a 3:2 ratio instead of the 3:3 turns ratio documented in this manual.
Remember this when you come to the assembly step for preparing and installing the output
transformer T1. The “primary” is still 3 turns, with a tap half way at 1.5 turns. The secondary (no
tap) will now be only two turns.
The chart below shows the measured power output vs supply voltage for the standard 3:3 winding
(Red line); at 12 V supply the output power of around 8 W is too high and likely to cause over-
heating or failure of the power amplifier transistors. If you wish to use a supply of 12 - 13 V the 3:2
winding style is more suitable and will produce 4 – 5 W output for 12 – 13 V supply. The graph
shows 40m but other bands are very similar.
 4

2 Assembly
2 1 General guidelines
Assembly of this kit is quite straightforward, most components are SMD and have already been
pre-assembled by the PCB factory. The usual kit-building recommendations apply: work in a well-
lit area, with peace and quiet to concentrate. Some of the other semiconductors in the kit are
sensitive to static discharge Therefore, observe Electrostatic discharge (ESD) precautions.
And I say it again: FOLLOW THE INSTRUCTIONS!!
Don’t try to be a hero and do it without instructions!
A jeweler's loupe is really useful for inspecting small
components and soldered joints. You’ll need a fine-
tipped soldering iron too. It is good to get into the habit of
inspecting every joint with the magnifying glass or
jeweler's loupe (like this one I use), right after soldering.
This way you can easily identify any dry joints or solder
bridges, before they become a problem later on when
you are trying to test the project.
You could also take photos with a mobile phone, and use
the phone’s zoom features to view the board in detail.
Triple check every component value and location BEFORE soldering the component!
It is easy to put component leads into the wrong holes, so check, check and check again! It is
difficult to de-solder and replace components, so it is much better to get them correctly installed
the first time. In the event of a mistake, it is always best to detect and correct any errors as early
as possible (immediately after soldering the incorrect component). Again, a reminder: removing a
component and re-installing it later is often very difficult!
Please refer to the layout diagram and PCB tracks diagrams below, and follow the steps carefully.
Use of a good quality soldering iron and solder is highly recommended for best results!
The following diagrams show the PCB layout and track diagrams of the QDX.
Tracks shown in BL E are on the bottom layer. Tracks shown in RED are on the top layer. There
are only two layers (nothing is hidden in the middle). Not shown in this diagram are the extensive
ground-planes, on both sides of the board. Practically everything on both layers that isn’t a RED or
BL E track, is ground-plane! The two ground-planes are connected at frequent intervals (not more
than 0.1-inches) by vias.
NOTE: the capacitor lead spacing on the PCB is 0.1-inches (2.54 mm) and most of the capacitors
are sized appropriately for this. From time to time, due to availability constraints, we may have to
use capacitors with 0.2-inch lead spacing (5.08 mm); this is not a mistake, it is just due to
component availability. In this case simply use a pair of long-nosed pliers (etc) to straighten out
the wires and make them spaced for the 0.1-inch pads.
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2 2 Parts list
Many components are SMD, pre-soldered to the PCB in the factory. Only through-hole
components need to be installed by the constructor. SMD components in the parts list are
identified in the Description column and by the text colour being purple.
Resistors
Qty Value Description Component numbers
3 0-ohms SMD R30, 31, 32
4 100-ohms SMD R22, 23, 24, 25
2 330-ohms SMD R2, 4
2 470-ohms SMD R28, 33
4 1K SMD R1, 6, 20, 21
1 1.5K SMD R34 (NOT INSTALLED)
12 10K SMD R3, 5, 10, 11, 12, 13, 14, 17, 18, 26, 27, 29
3 100K SMD R15, 16, 19
3 470K SMD R7, 8, 9
Capacitors (50V, Multi-layer Ceramic capacitors)
Qty Value Description Component numbers
1 22pF Label “220” C29
1 30pF Label “300” C31
2 47pF SMD C27, 32
2 56pF Label “56J” C10, 28
1 82pF Label “820” C11
1 100pF Label “101” C9
1 180pF Label “181” C20
1 220pF Label “221” C30
1 270pF Label “271” C7
2 390pF Label “391” C6, 19
2 470pF Label “471” C5, 14
2 820pF Label “821” C13, 18
1 1200pF Label “122” C12
3 10nF SMD C36, 44, 45
21 0.1uF SMD C15, 16, 17, 21, 22, 23, 24, 25, 26, 33, 35, 37, 39, 40,
41, 43, 46, 47, 49, 51, 53
11 2.2uF SMD C1, 2, 3, 4, 8, 34, 38, 42, 48, 50, 52
1 220uF 16V electrolytic Extra DC supply capacitor (see text)
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Semiconductors
Qty Description Component numbers
5 SMD: 1N4148 D7, 8, 9
6 1N4007 diode D1, 2, 3, 4, 5, 6
1 SMD: AMS1117-3.3 IC1
1 SMD: AMS1117-5.0 IC2
2 SMD: FST3253 IC3, 4
1 SMD: 74ACT08 IC5
1 SMD: 24C64 IC6
1 SMD: LM4562 IC7
1 STM32F401RBT6 IC8
1 AK5386 IC9
1 SMD: Si5351A 1
1 SMD: BSS84 MOSFET Q1
5 SMD: BSS123 MOSFET Q2, 3, 4, 5, 6
4 BS170: TO92 MOSFET Q8, 9, 10, 11
1 SMD: BC857 PNP T3
1 SMD: BC817 NPN T4
1 SMD: Red LED DIAG
1 3mm Red LED PANEL
Inductors
Qty Description Component numbers
6 SMD: 47uH L11, 13, 15, 16, 17, 18
4 47uH radial inductor L1, 5, 7, 9 (replace SMD inductors, see text)
1 T37-2 toroid (red), 2.40 uH (24t) L2
1 T37-2 toroid (red), 2.88 uH (26t) L6
1 T37-6 toroid (yel), 1.06 uH (18t) L3
1 T37-6 toroid (yel), 393 nH (11t) L4
1 T37-6 toroid (yel), 1.20 uH (20t) L8
1 T37-6 toroid (yel), 525 nH (13t) L10
1 T50-2 toroid – tapped, see text L12
1 FT37-43 10t L14
1 BN43-202 binocular, 3:3 T1
1 FT37-43 10t trifilar T2
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