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MagicBox T/R Switching System
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 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 and up to 10-watts of RF. 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.
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 a 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
This MagicBox T/R System can be ordered from the 4 State QRP Group here!!
Power Supply 10-15 volts dc; 120 milliamps
Audio Section (32 Ohm source and load)
QSK Mode Up to 50 WPM
Non-QSK Mode 1 second receiver delay
Transmitter Types Solid state or cathode keyed tube
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