The ATmega328 AVR microcontroller (IC1) is pre-programmed with firmware to control the LCD, buttons,
and GPS interface. The AD9850 Direct Digital Synthesis (DDS) module includes its own on-board 125MHz
crystal reference oscillator, and reconstruction filter components ready-mounted. On/off keying is provided
by the BS170 transistor Q1, and power amplification by another BS170 transistor, Q2, producing over over
150mW from a 5V supply on 30m. Finally standard 7-element low pass filter plug-in modules remove
harmonics of the transmission frequency.
3. Parts List
3.1 Resistors
R1
100K preset potentiometer, for LCD contrast adjustment
R2
No resistor – space is provided on the PCB only for reducing LCD backlight brightness
R3
No resistor – space is provided for a 100K resistor, if you want to do AVR firmware upgrades
R4
No resistor – space is provided for a 220K resistor, for smoother contrast adjustment
3.2 Capacitors
C2, 3
22pF (ceramic, marking 22, or 220)
C1, 4, 5, 6
10nF (ceramic, marking 103)
C7
No capacitor – space is provided for future enhancements
3.3 Inductors
L1
25 turns, FT37-43 core (black)
3.4 Semiconductors
Q1, 2, 3, 4
BS170 (note: only two are provided in the kit. The other two may be added for more power).
D1
No diode – provided for use with relay-switched LPF board kit
IC1
Pre-programmed ATmega328 microcontroller
DDS
AD9850 DDS module, including 125MHz reference oscillator and reconstruction filter
3.5 Miscellaneous
Two push buttons, S1 and S2
16-column x 2-row LCD (HD44780-compatible) with blue LED backlight
Printed circuit board, 80 x 37mm size
Wire for winding toroid
Socket for IC1
20MHz quartz crystal
Two 10-pin female header sockets
Two 4-pin female header sockets
16-pin female header socket
16-pin male header plug
Four 12mm nylon hex PCB spacers
Eight 6mm M3 screws
Relay RL0 – not supplied, provided for use with relay-switched LPF board kit
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