Technical Topics > Equipment
Software Defined receivers (radios)
weaksigs:
Is there anyone using software defined radios such
as the products offered by Flexradiosystems care to
offer comments?
I see several postings that seem to indicate a graphic
of a wide bandwidth (50-90 Khz for example) so
perhaps some of these postings come from owners of
software defined radios.
if so how do you like them---???
Thanks
ChrisSmolinski:
I have two SDRs, a netSDR and an SDR-14, both from RF Space. I love them, and could not imagine DXing without them.
I make recordings of the entire 43 meter band overnight, then go back the next morning looking for broadcasts. Basically, I never miss any pirate.
I'll be extending that to recording the 48 meter Europirate band also.
I keep meaning to finish up my SDR blog entry on http://www.hfunderpants.com/, I need to get back to that.
jFarley:
I've decided that I'd like to try an SDR, and I am looking seriously at the Lazy Dog Engineering LD-1B kit which for a couple hundred bucks might be a cost effective way to try one out before plunking down some serious cash. Has anyone tried this?
Chris, I'm fascinated by the fact that one can record a given band segment unattended; incredible power there. I'm still a bit mystified by the process. I'm guessing that the host software records a stream of I and Q data which is seen by the soundcard, and that this can be reviewed in a playback mode. Is this correct? How does one convert a particular frequency bin to an audio file?
ChrisSmolinski:
--- Quote from: jFarley on October 22, 2011, 1413 UTC ---I've decided that I'd like to try an SDR, and I am looking seriously at the Lazy Dog Engineering LD-1B kit which for a couple hundred bucks might be a cost effective way to try one out before plunking down some serious cash. Has anyone tried this?
--- End quote ---
I'm not familiar with that kit, but it looks like one of the sound-card interfaced SDRs. From their website, it is $285, plus then you need a decent sound card interface. And you still don't have all the issues with a sound card based SDR, vs a DDC SDR. FWIW, you're probably 2/3 of the way there cost-wise to the SDR-IQ from RF Space, which is $525 and ready to work.
--- Quote from: jFarley on October 22, 2011, 1413 UTC ---Chris, I'm fascinated by the fact that one can record a given band segment unattended; incredible power there. I'm still a bit mystified by the process. I'm guessing that the host software records a stream of I and Q data which is seen by the soundcard, and that this can be reviewed in a playback mode. Is this correct? How does one convert a particular frequency bin to an audio file?
--- End quote ---
Correct, the I and Q data is recorded to disk. In the case of the SDR-14/IQ/netSDR/etc, the interface is USB or ethernet, not a soundcard, but the principle is the same. In my case, I have some custom software I wrote that takes the recorded I/Q data, and displays a waterfall for the entire file, I can scroll up and down as needed, since the waterfall image could represent an hour or so of recorded RF.
An FFT is used to convert the sampled I/Q data into arrays of amplitude vs frequency data for drawing the waterfall. DSP demodulation routines are used to demodulate the recorded I/Q RF into audio, the same as with SDR software.
I can then drag select (with the mouse) around a signal of interest. So I can set the start and stop playback time, as well as the frequency range. Then I select the mode, and click Play.
I can also demodulate directly to a sound file, WAV or mp3.
Here's a picture of my app. It's ugly, but works for me :-)
mondomusique:
There is a new low price SDR RX/TX coming from RF-SPACE in 2012... The TX side is very low power, like a half watt or 1 watt or something.
http://www.sdr-one.com
There are a couple of cool things about this SDR... the TX side can do ESSB (Extended Single Side Band) up to 40 khz wide. If you can find a way to use its 1 watt to drive a linear SSB amp it could be a high quality RF source (not sure if that is enough power to drive a linear amp).
Also, its RX output is via SPDIF or I2S connection up to 192 khz receive bandwidth so can hook digitally to a suitable digital sound card input. I'm looking at VIA's upcoming sound processing chip VT1731 which will be cheap as chips and can handle 192 khz input via SPDIF or I2S connection. Also apparently a 3 year old Mac Book Pro can handle 192khz over SPDIF.
Quote from SDR-one Yahoo group:
--- Quote ---The SDR-ONE project is 3 weeks old. Boards were received. They were built in 4
hours. Receiver is working at all sample rates and S/PDIF is working at 48, 96
and 192 KHz. Amazing that my old MacPro that is 3 years old works at 192 KHz
over S/PDIF under Windows 7.
Here is a short video of the SDR-ONE in action using PSDR software.
http://www.youtube.com/watch?v=LO-htuuBl6I
Pieter
--- End quote ---
Okay, enough from me on SDR-ONE.
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