AmQRP AA-908 User manual

Micro908 Antenna Analyst “Assembly Manual”, v2 1 Copyright 2004, G. Heron, N2APB
~ Assembly Manual ~
Micro908 Antenna Analyst
The Micro908 is a flexible and re-usable control platform for ham radio projects. The Micro908
platform is designed to be easily operated on the bench as well as in the field. It is comprised of a
single 5” x 5” printed circuit board containing all components, connectors, controls, LCD, and two
daughtercards. The plastic enclosure contains an 8-cell AA battery back enabling convenient field
use. A number of standard ham radio peripherals may be connected to the Micro908: antenna,
paddles, a PC-style keyboard, headphones, an audio line to drive an SSB transceiver, a keyline to
drive a transmitter, your rig's audio in/out signals, and custom control lines via an auxiliary jack. The
first major software available for the Micro908 platform is the Antenna Analyst – an instrument that
automatically determines SWR and complex impedance characteristics of an HF antenna system.
Advanced features of DDS frequency control, LCD tuning, PC data collection and plotting, numerous
operating modes and easy software upgradability make this instrument attractive for homebrewers and
antenna enthusiasts.

Micro908 Antenna Analyst “Assembly Manual”, v2 2 Copyright 2004, G. Heron, N2APB
CONTENTS
Section 1: Introduction ......................................................................................................... 2
Section 2: Parts Inventory .................................................................................................... 3
Section 3: PCB Preparation ................................................................................................. 8
Section 4: Installing the Surface Mount Components ........................................................ 10
Section 5: Installing the Controls and Connectors.............................................................. 15
Section 6: Power-up and Test ............................................................................................ 20
Section 7: Installing the PC Board in the Enclosure........................................................... 21
Section 8: Troubleshooting ................................................................................................ 23
Appendix A: Parts List ........................................................................................................... 26
Appendix B: Schematic .......................................................................................................... 29
Appendix C: Component Layout ........................................................................................... 31
Appendix D: Fully-Assembled PC Board .............................................................................. 33
Appendix E: Mechanical Assembly Diagram ........................................................................ 34
Appendix F: Quick Reference Sheet ..................................................................................... 35
Appendix G: Loading New Software into the Micro908 ....................................................... 36
Appendix H: Making a Dummy Antenna for Testing ............................................................ 37
Section 1: Introduction
Welcome to the Micro908 Antenna Analyst Kit, a reprogrammable and multi-use microcontrolled instrument that will
provide years of reliable service in both the shack and the field when constructed according to this assembly guide.
This project involves the soldering of small surface mount technology (SMT) parts and other delicate components to a
printed circuit card, and it will take about six hours to assemble – perhaps several evenings or over a weekend. Once the kit
is assembled, the pre-programmed controller (the HC908 Daughtercard) may be inserted into place and immediate
indication of product operation will be seen.
This Assembly Manual provides detailed, step-by-step instructions on preparation of the components, installation of them
to the printed circuit board and enclosure, and basic calibration and operation of the instrument. Other documents provided
on the enclosed CDROM describe the technical overview and more detailed usage. Several useful software programs are
also contained on this Micro908 Resource CDROM, such as a software loader application and a terminal program.
Additionally, the CD contains information and full software source code that will be useful for those wishing to develop
custom software for the Micro908 platform.
Please regularly visit the Micro908 project website (www.amqrp.org/kits/micro908) to download updated versions of the
software, manuals and schematics. We are also maintaining a list of frequently asked questions (and answers) that will
surely be of help to you in building and using this kit. An even more complete and up to date Assembly Manual, with
additional photos (all in color) may be found at the Micro908 online site.
We’ve made every effort possible within reason to make construction and use of the Micro908 Antenna Analyst a success
for the builder. Please let us know how it works out for you or if you have any questions along the way. We thank you for
purchasing the Micro908 Kit from the AmQRP Club and we wish you good luck in building and using it!
Sincerely yours,
“The Micro908 Team”
George Heron, N2APB [e-mail]
Joe Ev erhart, N2CX [e-mail]
Tom (W8KOX) & Nancy (NJ8B) Feeny, [e-mail]
David Willmore, N0YMV, [e-mail]

Micro908 Antenna Analyst “Assembly Manual”, v2 3 Copyright 2004, G. Heron, N2APB
Section 2: Parts Inventory
Carefully review the contents of each parts bag and component supplied in the kit to ensure that you have everything
needed at the start of the project. If a part is missing, please contact us by email and we’ll get it out to you right away.
Surface Mount Components Sheet

Micro908 Antenna Analyst “Assembly Manual”, v2 4 Copyright 2004, G. Heron, N2APB
Controls & Connectors Bag
1 J1 BNC, pcb mount
1 J2 Serial port connector, DB9F
1 ENC Rotary Encoder
1 J4 Coaxial pow er connector, 2.1mm
1 J8 Socket, 1x12 pos'n (DSP out)
1 J9 Socket, 2x10 position, (DSP in)
1 J11 Mini-DIN, 6 pos'n (KBD)
3 J6, J7, J12 Audio jack, 1/8", pcb mount
1 J10 Socket, 1x8 pos'n, right angle
1 J14 Mini-Din, 8 pos'n (AUX)
1 W1 Jumper, Flexstrip, (LCD)
2 P1, P2 Pinheader, 2x34 (HC908) (cut 2 f rom 2x72 strip)
2 P3, P4 Pinheader, 1x2 pos'n (MON) (cut from 2x72 strip)
3 C7, C33, C34 Capacitor, 1 uF, Electrolytic, SMT
2 C5, C26 Capacitor, 10 uF, Electrolytic
1 C27 Capacitor, 47 uF, Electrolytic
1 C24 Capacitor, 100 uF, Electrolytic
1 R45 Potentiometer, 10K, miniature, pcb mount
1 S2 Slide sw itch, pcb mount, SPST
5 PB1, PB2, PB3, PB4, PB5 Pushbuttons, SPST, momentary contact
1 SPKR Speaker, miniature, 32-ohm
5 Pushbutton caps (black)
1 Heatsink - TO220
1 Knob, 1/4"-dia shaft, (ENC)
1 Nut, zinc plated, 4-40 (U1)
1 Machine screw , zinc plated, round head, 4-40 x 0.5" (U1)
4 Spacer, nylon, hex tapped, 4-40x0.25" (LCD)
6 Spacer, nylon, hex tapped, 4-40x0.375" (PCB+DDS)
16 Machine screw , pan slotted, #4-40x0.25" (PCB+DDS+LCD)
4 Machine screw , flat slotted, #4-40x0.25" (PCB-cover)
1 Desoldering Braid
1 Solder, 63/37 Eutectic, No-Clean Flux, @28 ga.
Overlay Bag (Included with Enclosure Option)
1 Front panel overlay
1 Side panel overlay
1 End panel overlay
1 End panel (drilled)
1 End panel (undrilled)
4 Enclosure screw s
4Enclosure rubber f eet
Battery Holder Bag
1 LCD Display, LCD, Hantronix, 16x2 STN, GRAY
1 J3 Battery holder, 8-AA cells
1 Flux Pen, No-Clean

Micro908 Antenna Analyst “Assembly Manual”, v2 5 Copyright 2004, G. Heron, N2APB
Semiconductor Bag
1 U1 Voltage regulator, 3-terminal, 7805
1 U2 Me mor y , SEEPROM, 512Mb
2 U3, U4 IC, Op Amp, LMC6484, SOIC
1 U5 IC, Audio Amp, LM386, SOIC
1 U6 IC, Level Translator, TC7SET08F, SOIC
1 LED1 LED, T1- 3 / 4 ( BUSY )
2 Shunt shunt, 0.1", 2 pos'n
3 D7, D8, D9 Diode, Schottky, 1N5817, DO-41
1 VR1 - DDS Option Voltage Regulator, 78L08, 8V (optional, f or use w ith regarg
a
1 Q1 Transistor, NPN, 2N3904, TO92
PCB Bag
1PCB PC Board
HC908 Daughtercard Bag (Optional)
1HC908 HC908 Daughtercard assembly

Micro908 Antenna Analyst “Assembly Manual”, v2 6 Copyright 2004, G. Heron, N2APB
DSPx Daughtercard Bag (Optional)
1DSPx DSPx for Micro908 assembly
DDS Daughtercard Kit Bag (Optional)
1DDS Ki
t
DDS Daughtercard Kit
Keyboard Cable Bag (Optional)
1 Cable Keyborad extension cable (6')
Keyboard (Optional)
1Keyboard Dauphin Mini Keyboard
Enclosure (Optional)
1Enclosure Pac-Tec LH-57 Enclosure (pre-drilled)

Micro908 Antenna Analyst “Assembly Manual”, v2 7 Copyright 2004, G. Heron, N2APB
Section 3: PC Board Preparation
Meet the Micro908 PC Board! You should become familiar with the orientation nomenclature that we’ll be using
throughout this manual.
Top, “Component” Side
Left Right 
Bottom, “Ground”, “Controls” Side
Left Right 

Micro908 Antenna Analyst “Assembly Manual”, v2 8 Copyright 2004, G. Heron, N2APB
Section 4: Installing the Surface Mount Components
Preparing for the job
The key to being successful with any construction project is selecting and using the proper tools. For projects using SMT
(Surface Mount Technology), the tools are easy to find.A magnifying lamp is essential for well-lighted, close-up work on
the components. Tweezers or fine-tipped pliers allow you to grab the small chip components with dexterity. Thinner
solder (.015”) than you might normally use is preferred because of its being quicker to melt and smaller in solder volume
on the component lead. Use of a super fine-tipped soldering iron make soldering the leads of these small parts
straightforward and easy. A clean work surface is of paramount importance because SMT components often have a
tendency to fly away even when held with the utmost care in tweezers – you’ll have the best chance of recovering your
wayward part if your table is clear. When the inevitable happens, despite your best efforts of holding an SMT part in your
tweezers, you’ll have lots of trouble finding it if it falls onto a rug-covered floor covered. It’s best to have your work area
in a non-carpeted room, for this reason as well as to protect static-sensitive parts.
Attaching SMT Components to the PC Board
We’ve supplied two items in this Micro908 Kit that will greatly help you successfully solder these small surface mount
components to the pc board. The first is a small coil of .015” solder. As described above, this thin solder is perfect for
soldering small SMT parts. Just wrap the solder around a convenient tube as shown below on the left) so you can easily
play out the solder as you go along in the board assembly. The other helpful item is the Flux Pen. By making the pads to
be soldered wet with the liquid flux, you are greatly helping the joint be clean and ready to accept the soldered component.
(Just press down a little on the tip of the flux pen and the liquid flux will start flowing out through the sponge tip.) In order
to solder these small components in place, having a fine-tipped, 600-700 degree soldering iron is essential, as illustrated in
the rightmost photo below.
Thin solder (.015”) is coiled around a glue stick. Flux pen applies flux to pads. Fine tipped iron solders in SMT resistor.
The trick to soldering surface mount devices to pc boards is to (a) pre-solder one of the pads on the board where the
component will ultimately go; (b) hold the component in place with needle nose pliers or tweezers on the tinned pad; (c) re-
heat the tinned pad and component to reflow the solder onto the component lead, thus holding the component in place; and
lastly (d) solder the other end of the component to its pad.
Attaching a Surface Mount IC
There are four surface mount integrated circuits to attach on the Micro908 pc board: U2 (memory chip), U3 & U4 (op
amps), U5 (audio amp) and U6 (a pretty tiny driver IC). Pre-solder the pad in one corner of the given layout then carefully
position the leads of the IC over its set of pads on the pc board. I generally use my fingers to carefully align the IC over all
its pads and then reheat the corner pad to reflow the solder onto the IC pin. This should leave the IC attached by that pin.
Again making sure the IC pins are aligned over all pads, carefully solder the opposite corner lead to its pad. This should
leave all other pins of the IC aligned over their respective pads, making it easier to solder them. Next solder each of the
other pins to their respective pads, being careful not to bridge solder across any adjacent pads or pins. If this does happen,
that’s okay! Just grab some solder wick (also supplied in the Micro908 Kit) and use it to draw off the excess solder, which
should be fairly easy and clean because of the solder mask on the circuit board.

Micro908 Antenna Analyst “Assembly Manual”, v2 9 Copyright 2004, G. Heron, N2APB
First corner pin of surface mount IC being attached. Solder wick easily absorbs excess solder between pins.
(IC shown being attached here is the DDS chip onto the DDS Daughtercard. The techniques are the same for the Micro908 ICs.)
Using the Component Layouts During Assembly
A helpful practice to develop is to mark the supplied Layout diagram as you install each component. As you go along, the
diagram will fill up with more and more marks, enabling you to more easily find the location of the remaining components,
and have confidence that you haven’t omitted installation of a component along the way.
A useful marking technique is to identify with a “dot” the location of the parts you are about to install, making it easier for
you to place and solder the part in the right spot. Once soldered in place, going back to the diagram and placing a full line
in that same spot will indicate that you’ve soldered it in place, as shown in the photo on the right.
The component layout diagram is a useful tool if you mark it up as you proceed along in installing the components.
1) Install components from Resistor Card 1 section of the SMT Sheet
Using the Component Layout Diagram in Appendix A as a guide, install the SMT components from the Resistor Card 1.
Check off each row as you complete installing those components.
QTY
[ ] 1 R46 Resistor, 10, SMT, 1206
[ ] 3 R11, R12, R14 Resistor, 49.9, SMT, 1206, 1%
[ ] 1 R7 Resistor, 330, SMT, 1206
[ ] 1 R8 Resistor, 1K, SMT, 1206
[ ] 1 R6 Resistor, 4.3K, SMT, 1206
[ ] 1 R44 Resistor, 4.7K, SMT, 1206

Micro908 Antenna Analyst “Assembly Manual”, v2 10 Copyright 2004, G. Heron, N2APB
[ ] 4 R37, R38, R39, R40 Resistor, 5.1K, SMT, 1206
[ ] 12 R1, R2, R3, R4, R5, R17, Resistor, 10K, SMT, 1206
R18, R22, R23, R27, R42, R48
2) Install components from Resistor Card 2
Using the Component Layout Diagram in Appendix A as a guide, install the SMT components from the Resistor Card 2.
Check off each row as you complete installing those components.
QTY
[ ] 1 R41 Resistor, 10.0K, SMT, 1206, 1%
[ ] 1 R28 Resistor, 22K, SMT, 1206, 1%
[ ] 4 R10, R13, R15, R49 Resistor, 47K, SMT, 1206
[ ] 4 R19, R24, R29, R51 Resistor, 71.5K, SMT, 1206, 1%
[ ] 4 R16, R21, R26, R50 Resistor, 220K, SMT, 1206, 1%
[ ] 3 R20, R30, 52 Resistor, 221K, SMT, 1206, 1%
[ ] 1 R25 Resistor, 549K, SMT, 1206, 1%
[ ] 4 R32, R33, R34, R54 Resistor, 1M, SMT, 1206
3) Install components from Capacitor & Diode Card
Using the Component Layout Diagram in Appendix A as a guide, install the SMT components from the Capacitor & Diode
card. Check off each row as you complete installing those components. Be careful to identify the cathode of the diodes on
this card. The cathode is the side of the diode with a single straight line on the schematic symbol, and with a (faint) single
straight line on the package. You will surely need to use your magnifying glass to see this mark. Orient the end of the
diode with the single straight line onto the pc board with the diode outline also containing the straight line indicating the
cathode.
[ ] 4 C17, C19, C21, C41 Capacitor, 220 pF, SMT, 1206
[ ] 2 C31, C32 Capacitor, 560 pF, SMT, 1206
[ ] 7 C18, C20, C22, C23, Capacitor, 0.01 uF, SMT, 1206
C28, C40, C42
[ ] 16 C1, C2, C3, C4, C6, C11, Capacitor, 0.1 uF, SMT, 1206
C12, C13, C14, C15, C25,
C35, C36, C37, C38, C39
[ ] 2 C29, C30 Capacitor, 0.33 uF, SMT, 1206
[ ] 10 D1, D2, D3, D4, D5, D6, Diode, Schottky, 1N5711, SMT (These diodes have faint cathode markings)
D10, D11, D12, D13
For now, don’t install this leftover part on the SMT sheet. But don’t lose it! (We just wanted to mention this up front!)
[ ] 1 U6 Integrated Circuit, Level Translator, TC7SET08F