Transcript Homebrewing From Scratch - South Canadian Amateur Radio

Homebrewing from a
Schematic
For the enthusiastic amateur
Why not build another kit?
Kits are self contained: no extra parts to
buy.
 You know what you’re getting: the project
has been tested and most of the kinks
have probably been worked out.
 Someone has thought out most of the
details for you.
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Why homebrew?
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You have ample, by which I mean too much,
free time.
You are afflicted with curiosity about how
circuits work.
You get free vision and psychiatric care.
You want to optimize.
You want a truly custom piece of equipment.
You want the satisfaction of knowing that you
are communicating around the world (or the
block) with something you made yourself.
Obstacles to homebrew success
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Start-itis.
You don’t have exactly the right part on hand.
 You don’t know what you want to build.
 You have more fun collecting parts than building
circuits.
 You think that you have to have lots of test equipment
to make a circuit work.
 You think that circuits are too complicated.
 You think that you have to be smart to make a circuit
work. (That’s patently false: look at me!)
 You think that it has to be finished in one sitting.
 You think that it should work the first time you turn it
on.
What do I build?
Start with easy projects.
 Simple test equipment like crystal
oscillators, RF probes, etc. are great.
 A regenerative receiver is fun.
 Shack accessories: dummy load,
antenna tuner, keyer, etc. are always
useful.
 Radios!
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Inspiration from the internet
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The homepage of KD1JV:
http://kd1jv.qrpradio.com
The homepage of Miguel, PY2OHH
http://py2ohh.w2c.com.br
The homepage of Onno, PA2OHH
http://www.qsl.net/pa2ohh
The homepage of PG1N
http://home.hetnet.nl/~pg1n/hambrew/hb_hf.ht
m
Numerous others
Inspiration from books and
magazines
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DeMaw and Co. from the ARRL: QRP
Notebook, EMRFD, QRP Power, More QRP
Power, W1FB’s Design Notebook, etc.
 The fine folks from RSGB and G-QRP club
including the book Low Power Scrapbook.
 The OU library has QST and Ham Radio
magazines going back decades.
 ARRL has most QST articles online for
members.
What about parts?
Do not expect to find every part that you
need for a project.
 Expect to improvise.
 Order more than you will need (your
friends, if not your spouse, will love you
for it.)
 Consider shipping costs as part of parts
cost.
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Where can I get parts for a project?
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Jameco, Digikey and Mouser carry most
everything you could possibly want: except
much in the way of RF components.
 Electronics Goldmine: Dealer of choice for
Parts Junkies. They also have the cheapest
copper clad board stock around.
 As a last resort: ebay.
 Keep in mind: leaded components are going
the way of steam passenger ships.
I need a variable capacitor for my
project!
Ocean State Electronics
 Nebraska Surplus
 Polyvaricons from Doug Hendricks at
QRPKits.com
 http://www.danssmallpartsandkits.net
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Some toroid cores would be nice
too.
Diz, W8DIZ runs
http://www.partsandkits.com.
 Palomar Engineers.
 Ocean State Electronics
 Last resort: ebay
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Ugly Construction
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Fast
 Ugly
 Easy to troubleshoot
 Can be easy to visualize
the circuit
 Is hidden when you put
the case on anyway
 Easy to modify
 Can write notes right on
the circuit board
Manhattan Construction
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Neat
Has all the advantages of
Ugly construction
FAST
Did I mention it is fast?
Can blend leaded
components with surface
mount components
Use to impress your non
techie friends
See Jim Kortge’s stuff at
http://www.k8iqy.com. He is
the master.
More on Manhattan Construction
Circuits are built on bare copper
substrate.
 Interconnections are made on pieces of
PC board glued onto the substrate.
 You can build testable subassemblies
and glue them onto the substrate when
you know they are working correctly.
 Can really simplify some tricky lead
placement.
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Manhattan/Ugly Subassemblies
Printed circuit boards
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Used primarily by
over achievers
 A must if you are
making more than
one of any project
 Free layout and
schematic tools are
widely available on
the internet
Tools
Simple rule: one can never have too
many.
 Practical rule: you will end up using very
few, so make sure the ones you actually
use are of good quality.
 What tools do I use?
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Kenn’s most often used tools
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Magnifiers, lots of ‘em, all shapes and sizes
Soldering iron, 25W, with the smallest chisel tip I could find
Soldering vacuum pump, because I make lots of mistakes
Small pair of needle nose and wire cutters
Forceps, curved and straight (for picking up small items and use
as soldering heat sinks)
Clip-on flood light
Exacto knife and saw
Super glue and/or hot melt glue
VOM
Frequency Counter
Crystal Oscillator (homebrew)
1 kHz square wave oscillator (555 timer, homebrew)
Dummy load, 20W (homebrew)
Huff Puff VFO (homebrew)
My magnifiers
Tools I have but hardly ever need to
use
Oscilloscope
 RF Signal Generator
 Audio Signal Generator
 RLC Bridge (antique, but it looks cool!)
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Parts to keep on hand ‘cause you
never know…
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Generic transistors: 2N3904, 2N3906, 2N3053, MPF102, 2N4401, 2N4403 etc.
Capacitors: NP0/C0G ceramic for tuned circuits, high value polystyrene for tuned
circuits and critical audio circuits, electrolytics or tantalum for non-critical audio,
power supply bypass, etc., silver mica for high power
Resistors 1/4W and 1/2W assortments, 1 or 2 watt 100 ohm, all in non-wirewound
compositions
Toroids in various sizes of 2,6 and 43 mix
Connectors of all kinds
Copperclad
Switches
Diodes: 1N914, 1N4007, varactors, etc.
IRF510/IRF511 for Power Amplifiers
Generic IC’s like basic op-amps, comparators, audio amps. There are hundreds of
choices. Match your wallet to your noise tolerance. I use LM741, LM383, etc.
because I can’t hear that well anyway.
Trimmer caps: 2-25pf, 3-60pf and 6-100pf are handy
If you don’t have all or any of this stuff for a last minute project, call me, I probably
do.
Circuits that I avoid
Old designs that you’ll never find the
right transformer, transistor or IC for.
 Circuits that are needlessly complicated.
 Circuits that are so poorly drawn that you
can’t follow the biasing and signal flow.
(You might redraw these if you are handy
with a computer.)
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Exception to the rule: 40673
Radio designs from the 1970’s used the RCA
40673 Dual Gate MOSFET EVERYWHERE.
 They have been out of production since the
early 1990’s.
 The Philips BF991 is still in production and
makes a good substitute, EXCEPT, it is a SMT
part. $0.45 from Digikey.
 It’s easy to make a small ½” X ½” PC board
subassembly for the SMT part that makes it
really easy to work with.
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Oscillator/Mixer/Amplifier IC’s
NE602/SA612 integrated circuit has
been hugely popular.
 It’s getting hard to find.
 SMD versions are readily available and
can be made into subassemblies.
 The TA7358AP is a cheaper and easier
to work with part, but it’s hard to find now
as well.
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Topologies: common designs
Humor me, I like big words.
 Direct Conversion receiver/transceiver
 Single Conversion transceiver
 Single Conversion transceiver with
crystal ladder filter
 Double Conversion transceiver (rare
these days)
 Transverters
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Direct Conversion Receiver
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NE602/SA612
74HC4066
40673/Dual Gate
MOSFET
TA7358
Single Ended
Diode Ring
Single Conversion with Crystal
Ladder Filter
Single Conversion with Crystal
Ladder Filter
Most popular topology you’ll see
 Popular because microprocessor
crystals are ubiquitous and cheap
 Most designs use NE602/SA612 or
TA7358AP.
 Exception: Check out Jim Kortge’s
2N2/40 which uses 2N2222 transistors
with diode ring DBM’s.
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3rd way: Phasing method
Check out PA2OHH’s website for his
phasing method transceivers.
 Software defined radios are using this
method with great success
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This is too much information! Where
do I start?
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Pick a simple project: a dummy load, a simple
transmitter, a regenerative or direct conversion
receiver, etc.
Lean on your buddies for parts and help.
Use the manhattan or ugly construction
method.
Try to understand the circuit and predict
voltages based on what you know.
Measure those voltages when the circuit is
working. How close are you?
From Schematic to Circuit Board
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Make a working copy of the schematic.
Check off parts on the schematic as you work.
 Make notes directly on the board with a permanent ink
pen.
 Dry place your parts before you plugging in your
soldering iron.
 Beauty doesn’t count.
 Start from outputs and work toward inputs.
 Power your work as soon as you can to test each
section.
 Fuses and circuit breakers are our friends.
 Work slowly. Enjoy yourself. This is supposed to be
fun. Savor the moment.
Thanks so much for getting me into
this, but my project doesn’t work.
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Blame yourself first.
Smoke is bad. Parts should only have smoke on the inside.
Did you double check all junctions?
Looking at the part from the bottom front, the pinout for the
2N3904 is EBC. Really.
Remember electrolytics/tantalums are polarized. They are also
mildly explosive, given the right conditions.
Diodes have a stripe. Did you know that?
Take your time. This is supposed to be fun.
A Volt/Ohm-meter is worth 10 oscilloscopes. Check voltages,
continuity and component values before worrying about
waveforms.
Call for help. Hams LOVE to help people. Even if they have no
clue how to help right at the moment. We can always figure it out
together. Two heads are better than one, unless you only have
one hat.
I built it, it works, now what?
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Cases are expensive to buy, but cheap to make.
 Shielding is usually unnecessary when using
ugly/dead bug/manhattan construction thanks to the
ground plane.
 Knobs are obscenely expensive. Try making them out
of hardware dowels.
 Circuit components are cheap compared to
interconnects and switches.
 Use MS Word or Publisher to print out faces for
cabinets. Laminate and stick or stick and spray.
 Why spend $25 on a case and knobs for a project that
cost $5 for components?
What I can do for you
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Parts: if you need that one elusive part that will
complete your project and your life, call me.
I have a small test bench and a little bit of
troubleshooting knowledge if you’re really
stuck.
I have most of the popular QRP project books
if you want copies of a schematic or project.
If you need some internet links to get you
started, give me a call or shoot me an email.
I can email this presentation to you as well.
About your presenter
Kenn Goodson
KA5KXW
(405) 364-8060 Home
(405) 579-6731 Work
[email protected]