• Tweet

MbotenGatek – DDS of this project has actually been my VU3CNS Completes in early 2012 was, however, a new opportunity to write here today. I’m working on this project only on weekends only, so it takes 3 weeks very interesting at the time of manufacture

I do not use in the manufacture of PCB printed DDS, but my apartment is directly on a PCB hole in accordance with the habits of my hobby since then. Implementation in a good PCB will certainly give better results and the beautiful neatness. But sometimes, the beauty of homebrew products actually sticking out when we can highlight the hallmark of handmade and chaotic wiring in the system that we build, but it all depends on the tastes of each individual, in this project I am quite satisfied with the performance and appearance of the whole I have the system up.

Incidentally, I have a DDS IC from Analog Devices AD9851 production is a major component in this project. The project was designed by one of India with Ham callsign VU3CNS, you can find documentation and resources to make this project complete in http://www.hamradio.in/circuits/dds.php

The project includes several blocks as follows:

Blocks PSU – Power Supply Unit
This block contains a down converter transformer is rectified by a diode bridge, and is equipped with two 7805 voltage regulator (output 5 Volt) to distribute the block MCU and DDS, as well as the regulator 7812 to distribute the RF amplifier circuit just beyond the DDS block.
16F628A MCU block
MCU block led by two pieces of 16F628A, 16F628A used to mendrive an IC AD9851 to perform its function as a DDS, while the other 16F628A used for switching for additional blocks in accordance with the amateur bands are covered in this VU3CNS project. One example application is the band AD 80, the IC can provide a HIGH output on port AD 80, where the port can be used to move the Relay on BPF or LPF corresponding band.
AD9851 DDS block
DDS block is actually divided into 3 main sections, namely DDS itself, which generates a signal with frequency as expected, LPF (Low Pass Filter) is used to convert the DDS output in the form of non-continuous signal into a continuous signal, the LPF will also eliminate the signal -harmonic signal produced by the DDS. The last part is an RF amplifier is used to adjust the amplitude of the DDS output as a whole.
This project has many uses, of course, the main usefulness is as a signal generator with a specific frequency. I’m setting this DDS with a maximum output of 50MHz, which is used for AD9851 DDS IC with 30MHz clock * 6 = 180MHzis better able to generate maximum output with a frequency of 1/3 * 180MHz = 60MHz, although there may also provide output with a frequency higher of 60MHz, but this is not recommended.

In the implementation of the DDS, I did not add the final amplifier, so the output is displayed is the output of the DDS who has gone through a series of LPF. At frequencies lower HF bands, the amplitude of the output is still quite strong, but at higher bands, I freluensi menyampelnya on an 30-MHz output has an amplitude that is small enough. So the presence of RF amplifier behind the DDS I think it is quite important.
Tips I can give in making this DDS is adding a substantial heatsink on the AD9851 DDS IC, because the heat released on her tiny body just feels to the fingers during operation. Because the DDS IC prices are quite expensive, of course, we do not want to ruin it, well enough heatsink which is expected to be able to protect it from damage due to overheating. In this case, I use an aluminum heatsink of the former rail pair of curtains that have been unused, we can adjust its size and easy to apply. For leveling of absorption, do not forget to apply a silicon gel on the body as needed AD9851 and the heatsink to be installed.
Following the general performance of DDS projects that I have made this: http://youtu.be/M432rTFl2-Y

http://yd1chs.wordpress.com