Software defined radio (SDR)
Posted: Sun Oct 28, 2012 3:13 pm
As a follow up to my question in the General section of this forum
Here is my quick and dirty attempt at an SDR. Caution, I was getting 100% CPU spikes the longer the schematic was in use.
It consists of a wave player loaded with an example test wave file of captured CW signals across the frequency spectrum (found on the internet), feed into a frequency splitter to act as a frequency range selector, then into a variable state filter which acts as a sort of upper side band, lower side band, band pass filter to remove interferring signals/noise. Outputs are shown on a FFT display and trogluddite's waterfall display (from the SynthMaker forum).
The way it should work in theory is that a narrow frequency range is selected from the full spectrum signals using the frequency splitter, then further enhanced with the filter. Signals are determined by monitoring the displays and looking for peaks and intensities.
It sort of works. I was able pull out a single CW morse code signal. Obviously this needs a lot more work such as the waterfall display would need to be more persistent and scroll more upwards than at an angle, the FFT display, waterfall display, and frequency spliter would all need to be lined up on on top of the other with accurate frequency ranges, the frequency splitter needs a way to select a more narrower range of frequency, AM signals would need to be de-modulated, etc. FYI - I had to delete the wave file otherwise it was too large an fsm file to upload. The test wave file can be found here: https://sites.google.com/site/g4zfqradi ... r_software
acg2010 wrote: Has anyone considered trying to make a SDR with Flowstone?
Beside the necessary broadband radio receiver hardware (readily available), seems like all that would be needed would be a spectrum display or waterfall display with persistent scrolling, necessary filters (lowpass, highpass, bandpass), a way to select part of the spectrum maybe similar to the SynthMaker frequency splitter module, and a way to play the resulting waveform using a wave player module. Iam probably over simplying it and some parts (algorithms) might have to be coded.
I have reviewed the internet literature and you can find many SDRs already, most programmmed in C++ or even java (on-line versions). There is one good article on programming a simple version of SDR in Max/MSP.
Seems like a simple broadband radio receiver could be developed (like the Flowstone board) and sold as a kit along with the software similar to Funcube.
...just an idea.
Here is my quick and dirty attempt at an SDR. Caution, I was getting 100% CPU spikes the longer the schematic was in use.
It consists of a wave player loaded with an example test wave file of captured CW signals across the frequency spectrum (found on the internet), feed into a frequency splitter to act as a frequency range selector, then into a variable state filter which acts as a sort of upper side band, lower side band, band pass filter to remove interferring signals/noise. Outputs are shown on a FFT display and trogluddite's waterfall display (from the SynthMaker forum).
The way it should work in theory is that a narrow frequency range is selected from the full spectrum signals using the frequency splitter, then further enhanced with the filter. Signals are determined by monitoring the displays and looking for peaks and intensities.
It sort of works. I was able pull out a single CW morse code signal. Obviously this needs a lot more work such as the waterfall display would need to be more persistent and scroll more upwards than at an angle, the FFT display, waterfall display, and frequency spliter would all need to be lined up on on top of the other with accurate frequency ranges, the frequency splitter needs a way to select a more narrower range of frequency, AM signals would need to be de-modulated, etc. FYI - I had to delete the wave file otherwise it was too large an fsm file to upload. The test wave file can be found here: https://sites.google.com/site/g4zfqradi ... r_software