Advertisement
2000, Red Hot Radio – Unauthorized Copying or Publication Prohibited
Introduction
Thank you for buying a NorCal QRP Club SMK-1 kit.
We're sure you will enjoy learning/practicing surface
mount construction techniques by building the SMK-1.
As a bonus, when built, the SMK-1 is a fully working 40m
CW transceiver that you will be able to use on the air to
make contacts!
The idea to produce the SMK-1 kit came from Doug
Hendricks, KI6DS, who thought it would be a good idea
to have a cheap learning tool to get hams used to doing
surface mount construction, since that's the way virtually
the whole electronic industry has gone and will inevitably
become the technique of necessity for ham kits in the
future.
All you will need to turn the SMK-1 into a fully working rig
is a case, some knobs, an antenna jack, a power jack, a
key jack and an earphone jack. Fortunately, the New
Jersey QRP Club has come to your rescue here! They
are supplying a custom designed PCB construction
case, knobs and connectors kit for the SMK-1 for only
$10 including shipping to anywhere. You can order one
from them by sending a check or money order for $10
made payable to George Heron to:
George Heron, N2APB
2419 Feather Mae Court
Forest Hill
MD 21050
USA
The SMK-1 contains over 80 components. Most of them
are surface mount parts. Some parts, like crystals,
trimcaps and pots, are either too expensive or not easily
obtained in surface mount packages so through hole
parts are used.
The surface mount parts used in the SMK-1 were
chosen to be large enough for most hams to be able to
handle them with a small pair of tweezers and solder
them in place using a fine-tip soldering iron. They are not
the smallest surface mount parts by a long way, but they
are small. I have personally built several kits now without
using a magnifier, but I do recommend you use one if
you have one! It will make life a lot easier for you,
especially if your eyesight isn't quite what it used to be!
I recommend that you use a 1/16
soldering iron tip, preferably temperature controlled, and
use 0.020" silver solder (although just about any solder
will do!). You will need a small pair of angled tweezers to
The SMK-1 Construction Manual
th
inch or smaller
be able to handle the components with dexterity and
without damage.
Have fun building your SMK-1 kit – please let us all know
your progress and give us your comments/feedback on
the QRP-L email reflector.
General Description
The SMK-1 circuit is basically a modified Tuna Tin 2
transmitter integrated with a modified MRX-40 receiver. It
is a further modification of the modified TT2/MRX-40 that
I built for the indoor foxhunt at Pacificon 1999. All this is
fitted onto a small 2.475" x 2.25" PCB.
The transmitter consists basically of the two 2N2222A
transistor lineup of the original TT2 but with electronic
keying. A key-switched crystal oscillator that has some
degree of VXO feeds a medium power packaged version
of the 2N2222A as a final in class A mode. After
harmonic filtering, the result is about 350mW of fairly
clean transmit power on 7.040MHz (+/- a bit).
The RX
front
end
mixer/oscillator with a crystal VXO. The RX is a direct
conversion receiver, so you will hear both sidebands as
you tune through a station. The input stage of the NE602
has been biased a bit harder than normal by R1, a 22K
resistor (this resistor may need tweaking, if your receiver
is overdriven, increase the value of this resistor. Try 27K
or 39K). This gives the device more conversion gain.
The audio output of the NE602 direct conversion front
end goes through a FET switch that serves to mute the
audio to an acceptable sidetone level during TX and then
on to a standard LM386 audio power amplifier running
as much gain as it can.
The three controls on the front panel of the SMK-1 are
(left to right as you look at it) RF attenuation, RX tuning,
TX tuning. Operating the SMK-1 requires a little
knowledge of where you are receiving and transmitting –
there will be more on this in a later section of this
manual.
2
uses
the
ubiquitous
NE602
Advertisement
