Saturday, May 26, 2007

SDR-IQ Day 2 Experiences

OK, I figured out what I was doing wrong when I play back recorded SDR-IQ RF files in Spectravue... you need to explicitely tell the program what frequency the recording was centered on when playing back. If the "Center Frequency" in the spectrum was 620 kHz, then you need to tell the program that on playback. I also noticed that, for some reason, the "Invert Spectrum" option was defaulted 'on' every time, so the frequency of the stations in the 190 kHz of displayed spectrum were inverted (e.g. if I was centered on 970 kHz, the next higher station would be 960 rather than the expected 980 kHz). Once you play with Spectravue for an hour or two, everything makes perfect sense.

I did several top of the hour recordings to see exactly how this all works. It was great fun to be able to go back and listen to the TOH IDs of 19 different AM stations as many times as I wanted, and adjust the bandwidth and mode (AM/USB/LSB) for each one. I fired up Total Recorder, and by picking the "software" audio input was able to record each of the stations' audio, as I listened, to an MP3 file.

I noticed some interference-like stuttering in the audio at various times, which seems to go away when I cut the spectrum down to 150 or 100 kHz from 190 kHz. I am using a 4-year old 1.8 GHz Dell desktop, and I am presuming that I might be taxing the processor/bus a little too much at the high setting.

(Update 6/17/07 - I moved over to a newer Compaq 3100+ Sempron machine and there are now no stuttering or gliches)

I'm happy with the SDR-IQ!

To learn more about the SDR line of radios, join the Yahoo Groups SDR-IQ or SDR-14

Friday, May 25, 2007

New SDR-IQ has Arrived!

(5/25/2007) I just received my new SDR-IQ software-defined radio from Universal Radio - it seems like they got a small shipment in, and I had been monitoring their website for the announcement. The version I purchased was just the bare board, not the complete unit mounted in a case (those seemingly are still waiting for FCC approval). Cost was $399, quite reasonable considering its capabilities.

The current link to the radio on their web site is: SDR-IQ

[UPDATE 5-26-2007: Universal announced they are sold out of the boards, and would have more later]

[UPDATE 9-7-2007: The Universal site no longer lists the bare board version anymore, but appears to have the complete SDR-IQ with case available on their web site]

I will be writing more about the SDR-IQ in the future, but was very impressed by its operation the few minutes I spent with it tonight. Most exciting is the ability to see the spectrum across 190 kHz of bandwidth in real-time, and the ability to record that spectrum to hard disk for later listening (as if it were live). I had a small glitch with the included Spectravue software on playback of an RF recording, as the frequencies of spectrum displayed were different from what I had recorded. But, I presume this is due to "pilot error" on my part, and I will work more with it in the coming days to see how it all works.