AD9833 DDS Reference for a 12-18 MHz PLL Oscillator
project is a 160-40 meter band SSB/CW transceiver. It has a PLL with a
AD9833 DDS reference. The design allows a 1.5 Hz resolution, low noise
and flexible frequency management like in most modern transceivers. The
photo below shows the control unit. It has a ATMEL microprozessor and a
128x64 pixel graphic display. The above circuit board shows the VCO,
PLL and the 10.7 MHz IF receiver with a tunable crystal filter (0.5-3
The heart of my 160-40m transceiver is the PLL. The AD9833 DDS is the
reference oscillator. The VCO frequency is divided by the factor of 16.
The result is compared in the phase/frequency comparator 74HC4046 with
the output frequency of the AD9833 DDS. The output signal of the phase
comparator is filtered in a TL071 operational amplifier low pass
filter. The resulting output voltage drives the BB201 varactor diode of
the VCO. The AD9833 was chosen because of its low supply current of
only 5 mA.
See the circuit diagram of the PLL here.