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Author Topic: Arduino DDS AF/RF Signal Generator???  (Read 39939 times)

K4TFJ

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Arduino DDS AF/RF Signal Generator???
« on: June 25, 2014, 01:57:19 PM »

Anyone creating an Arduino controlled AF/RF signal generator with selectable (and hopefully calibrated) output levels??

There are many Arduino based VFO designs that fit the bill for the base for such a project.  If you add a little bit of level control and some modulation choices, then these Arduino VFO's can become a basic piece of test and alignment for the homebrewer or income-limited amateur.

I had to borrow an HP sig-gen to align my HF radio's s-meter for instance, as it needed a signal source of 50uV/-73dBm and 0.8uV/-107dBM. Would have been nicer to build my own! Maybe a display to show the freq, modulation type, uV and dBm.
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N0NZG

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RE: Arduino DDS AF/RF Signal Generator???
« Reply #1 on: July 27, 2014, 07:50:32 PM »

http://www.ad7c.com/projects/ad9850-dds-vfo/

I build one of these based on the AD7C design. He built his code around the Arduino Uno. I modified the code to work with the Mega 2560 as well. Right now I just have a very nice  50hz – 35 mhz signal generator. In the future I plan on adding a diode ring mixer ( mini circuits labs SBL-1)  so that I can AM modulate the signal as well. The output is adjustable on all of the DDS boards I have worked with so far. It can be measured with an RF probe and a DMM or an O-scope if you have one.  One issue to note on all of these is The frequency  on the display is the requested frequency and not the “real output frequency.  There is a place in the code were the DDS chip clock  is divided by a constant to give the output frequency. You can fudge the constant number to give better accuracy at the high end , low end, or specific band. Beast case accuracy is usually +- a couple hundred HZ from the requested frequency. It would be an easy affair to set the output at 0dbm and then make some attenuator pads to divide down the output. IF you need the code for the Mega 2560 shoot me an E-Mail. I  am good on QRZ
73, Jeremy
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