MagicBox V1R2B Assembly Manual

Assembly Manual

V1R2B-Rev1.0D

for 4 State QRP

MagicBox - Solid State Transmit/Receive System

Designed by: Jim Kortge, K8IQY

Copyright 2009-2012 - All rights reserved

This system is the result of some brainstorming with Terry Fletcher, WA0ITP and Joe Porter, W0MQY
at the Dayton Hamvention in 2009. We were talking about kits that might be suitable as revenue
generators to fund the Ozarkcon activities in 2010 and beyond. The "MagicBox" project is the result.
It is an all solid state, Transmit/Receive switching system that allows one to connect single band CW
transmitters (up to a maximum of 10 watts) and receivers together to turn the pair into a transceiving
station, "like magic". The system can be used on any band from 160 through 10 meters. It can handle
both solid state and cathode keyed, tube transmitters. It supports full QSK CW up to about 50 WPM.
And, a non-QSK mode is also provided, for those who don't like QSK CW.

There are five pieces of functionality within the system. First, is a keying circuit to turn on the
transmitter. Second, is a PIN diode switch used to connect the transmitter to the antenna so that it can
transmit and also to isolate the output impedance of the transmitter from loading the receiver. Third, is
a four element, series-shunt switch that disconnects the receiver from the antenna and shorts the
receiver input to ground while the transmitter is transmitting. Forth, is another series-shunt switch
(three elements) used to disconnect the receive audio from the speaker (headphones) during transmit.
Fifth, is an sine wave audio oscillator and series switch that supplies side tone audio to the speaker
(headphones) during transmit so that transmit keying can be monitored. All of the control timing for
the system is supplied from an AVR ATtiny2313 microprocessor.

1

The next pages contain an image of the supplied printed circuit board and the schematics for the
system.

2

3

4

PCB Stuffing

Stuffing the PCB will be done by installing all of the connectors and headers. Following that, all of the
resistors will be installed, starting from the lowest value and proceeding to the highest. Then, all of the
capacitors will be installed, using the same scheme. That will be followed by the inductors and
transformers, and then the diodes. When all of the passive parts are on the board, groups of integrated
circuits and transistors will be installed followed by simple tests to assure that circuits are active and
performing to specification. It is highly suggested that you print out both schematic sheets and use a
highlighter to mark each component as it is installed. This will assist you later on if you have parts left
over and wonder where they were supposed to go.

Connectors and Headers

[ ] Start construction by installing Power Jack J1. Hold this part toward the rear of the PCB so that is
projects out from beyond the edge of the board.

[ ] Install the 4 audio jacks at locations J5, J6, J8 and J9.

[ ] Install the 3 BNC jacks at locations J2, J3 and J4.

[ ] Install a 2-pin header at locations J7, J11, J12, J13 and J14. Supplied with the kit is a break-a-way
20-pin header to be used for the 2-pin and the 3-pin headers. Use sharp diagonal cutters or a hobby
razor saw to make the appropriate cuts.

[ ] Install a 3-pin header at J10.

[ ] Install the 20-pin IC socket at location U1. Make sure to get the orientation correct; match the

notch in the socket with that of the silkscreen overlay. Once it is soldered in, it cannot be removed

without destroying the printed circuit board.

5

Your PCB should look like this:

Resistors

[ ] Install the large, 1 watt, 180 Ohm (Brown-Grey-Brown) resistor at R12. This is the only 1 watt
resistor; all of the others are 1/4 watt. Note: The leads of this resistor should be bent as
shown in this detailed photo, so that it will fit the hole pattern and slightly elevate the
resistor above the board for cooling.

[ ] Install 220 Ohm (Red-Red-Brown) resistors at R36, R43 and R44.

[ ] Install 470 Ohm (Yellow-Violet-Brown) resistors at R3, R4, R14, R18, R35, R40, R42, R47 and
R48.

[ ] Install 4.7K Ohm (Yellow-Violet-Red) resistors at R1, R2, R7, R8, R9, R11, R13, R15 (next to
R18), R16, R17, R20, R21, R22, R23, R24, R26, R27, R28, R29, R30, R31, R33, R34, R37, R38, R39,
R41, R45 and R49. Since there are so many resistors of this value, it is suggested that they be installed
in groups of 7, 7, 7 and then the remaining 8, shown by the colored highlights.

[ ] Install the 36K Ohm (Orange-Blue-Orange) resistor at R25.

[ ] Install 47K Ohm (Yellow-Violet-Orange) resistors at R10 and R19.

[ ] Install the 10M Ohm (Brown-Black-Blue) resistor at R46.

6