Another weekend project is this variable frequency oscillator based from dds chip. I found this project useful in my home brew dsb transceiver and testing several filters and rf amplifiers.
I bought the dds chip from Lazada, the cloned arduino is from Alexan, and the lcd module is from E-Gizmo. The dds is able to generate an rf signal from 1MHz to 30MHz with adjustable tuning steps from 10Hz, 50Hz, 100Hz, 500Hz, 1KHz, 2.5KHz, 5KHz, 10KHz, 100KHz and 1Mhz.
A broadband rf amplifier is also included to boost the amplitude of the dds signal. Around 3V peak to peak was measured at 7Mhz and decrease gradually on higher frequencies.
Credit is given to AD7C in which the schematic and the arduino code was copied. The broadband rf amplifier is not shown however.
A beautiful 7MHz sinusoidal wave can be seen in my Tektonix oscilloscope. One thing I observed however, the 125MHz reference clock is heating specially when the dds module is supplied with 5V but this did not affect the quality of the signal output generated by the module. One option is to use the 3.3V supply found in arduino uno but the signal level from the module is reduced. EMI and other interference could also stop the module from generating rf signal. ---73 de du1vss
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