Saturday, June 16, 2012

Afedri SDR-Net - Better Than Anticipated?

The screendump below is from the 31 meter band with rather high signal levels. I am running the Afedri at +24 dB VGA, which equals around -104 dBm sensitivity. At this VGA setting it's in fact a tad more sensitive than the NetSDR, yet there is no indication on the waterfalls of any overload. Very cool. This may indicate that the Afedri will perform well during the coming autumn's MW openings.
Earlier today I also did a recording test, with both SDRs recording 1250 kHz into an internal hard drive simultaneously. No hiccups or stuttering, and very low CPU. Maybe the Ethernet connection makes it easier for the CPU and that the network board does some or most of the processing. I don't know, but what I do know is that when you record from USB based SDRs stuttering may often be a problem.

Two Net-based SDRs Playing Together

If you have a router or a switch, you can connect several net-based SDRs to one PC. And if you use SDR-Radio, which allows multiple instances of the program to run, you can operate them simultaneously. Since I have one RF Space NetSDR and one Afedri SDR-net I decided to test this. What is needed are different IP addresses for both (or all) SDRs, and different ports. I am no network geek so I had my portion of trial and error, but with the help of SdrNetSetup and disconnecting and reconnecting the Afedri I got both SDRs to play along. On the jpg below the Afedri identifies as "SDR-IP".

Both SDRs are displaying a 1250 kHz span, with little CPU load. Another interesting observation is that when the SDRs are tuned to the same frequency, their audio appear to be perfectly synchronized. There is not the slightest trace of echo or other audio artifacts. Diversity reception, anyone?