It was a good day today. At long last, I have received my WBX transceiver boards for the USRP!
I have been waiting for this transceiver board for quite some time now because I didn’t really have and transmit capabilities in the VHF and UHF bands. This board was expected to cover 50 MHz to 1 GHz, so it was perfect as VHF/UHF transceiver. On January 13, Matt Ettus has finally announced that the WBX transceiver is now available.
There were more good news in the same announcement. First, the specs have changed and the WBX transceiver actually covers 50 MHz to 2.2 GHz (instead of up to 1 GHz). The improved specifications come at an improved price, namely $450 instead of the expected $400; however, the introductory price for first batch was kept at $400. Needles to say, I ordered mine within a few days.
What do I want to do with a 50 MHz – 2.2 GHz full-duplex transceiver, you might ask… Satellites of course! With most linear and FM satellites working in the VHF and UHF band, this transceiver seems optimal. With the new specs it can even cover the 1.3 GHz L-band, which I think is used for AO-51 uplink. Even in non-amateur space communications this transceiver board provides interesting opportunities: Weather satellites on 137 MHz and 1.7 GHz, GPS on 1.2 and 1.5 GHz, space research S-band communication uplink on 2.1 GHz, and probably many more that I do not remember.
Some specs I gathered from the mailing list and Ettus website:
- The minimum noise figure over the whole band is 5-6 dB
- Typical IIP3 is 5-10 dBm
- Typical IIP2 is 40-55 dBm
- TX power 50-100mW up to 1 GHz, 30-50 mW above 1 GHz
You may say the noise figure is not too impressive and indeed, you may find something with a few dB’s better for such wideband coverage. But does it matter? You will most likely have a long coax cable going form antenna to the receiver, therefore, you will need a low noise pre-amplifier at the antenna anyway and that will improve the system noise figure significantly. Since initially I will be focusing on VHF/UHF applications, the only useful comparison for my case would be to the TVRX daughterboard, which covers 50 MHz to 850 MHz and has a noise figure of 8-10 dB. The WBX is significantly better than that.
What’s the plan?
First, I have to start upgrading my GNU Radio installation(s) to the latest development code to get the drivers for this board. Currently, most of my computers run GNU Radio 3.2.2 on Ubuntu 9.04 simply because of the convenience of having the DEBs. I did, however, make some test builds last week and had no trouble installing the current development code. So this should be no problem.
Once I have the software installed at least my laptop, I’ll take it to the lab to check the specs. Although receiver performance measurements covering the whole spectrum are available, it is always good to make the measurements yourself, just for the sake of exercise 😉
Finally, I’ll work on the software. The building blocks are all there and there are even examples implementing most of the functionality I’m looking for. Unfortunately, the proof-of-concept like examples leave a lot to be desired on the ergonomic areas of the UI. I don’t know if I’ll be able to do much better in wxPython; I have a few ideas for minor improvements that would have significant impact. In the long run, I’d like to have a C++/Qt implementation anyway.
I’ll post updates and videos as I make progress.
Edit 2010-01-27: Schematics of the WBX transceiver are now available in the Ettus document repository.
