WBX receiver test on the air: Copenhagen VOLMET

I have been quite busy during the last weeks doing overtime at work, nonetheless, I have managed to carry out some small on the air tests of my newly acquired WBX transceiver boards for the USRP and GNU Radio. Tonight, I tuned in to Copenhagen VOLMET that transmits AM on 127.000 MHz.

As you may notice, I have used a modified version of the SDR transceiver I have been testing a month ago. The modification consisted in changing the available bands to include 144-146 MHz and tune initially to 145 MHz. Without these changes the SDR transceiver program would not start, since it is written to be a HF transceiver but the WBX can not tune below 50 MHz. Actually, I noticed that the WBX transceiver can not tune below 69 MHz but that is a different story. I also increased the receiver gain from 1 to 25 dB and changed TX antenna to None (i.e. auto).

You can watch the video in high definition on YouTube.

There is something odd about the SDR transceiver. The code appears to be generated by the GNU Radio Companion but there are no .grc files – only Python files that are executed from the command line like regular GNU Radio scripts. I can imagine that they used the GNU Radio Companion to create the initial prototype, then they fine tuned the generated python scripts by hand. In such case there is no point in including the .grc files in the distribution.

By the way, I am recording all my on the air tests with the WBX and I should have a video of all the tests coming soon. I will also report the finding, it’s just that I have had very little time.

Author: Alexandru Csete

Embedded software engineer in the satcom industry during the day. Radio amateur and SDR hacker during the night.