The WBX 50-2200 MHz transceiver

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.

Gpredict on the Eee PC 701

Now that I have Ubuntu 9.04 runnign on my Asus Eee PC 701 it was very easy to get Gpredict up and running. After a few configuration tweaks related to the views it runs and looks very well even on this small 800×480 pixel display!

Watch in high resolution.

Thus, I have now following hamradio applications running on the Eee PC:

First Impressions of the Arrow II Antenna

I heard about the Arrow II Satellite antenna quite some time ago and even seen a lots of videos about it on YouTube. Unfortunately, whenever I look for an opportunity to get one, I couldn’t find it anywhere in Europe. Until recently, when I learned by a coincidence that Antenna Warehouse is also shipping them to Europe! Didn’t have to think long before I decided that I can’t live without one and so I ordered one on July 21st, 2009.

The price I had to pay was a bit of an issue. Although the antenna costs $139, which I find very acceptable, the shipping and import costs from US to Denmark are usually a very traumatic experience. This time I only had to pay $39 for the shipping, which is fine, but then came the EU import duty and Danish VAT, which was an additional $70.

So was it worth the price? Well, let me see:

  • It took two and a half weeks for the antenna to arrive but this included one week delivery to Antenna Warehouse — they did not have it on stock just when I ordered. I find this delivery time acceptable given the circumstances.
  • Once I had the antenna in my hand, it took me less than 5 minutes to assemble it without looking at the instructions.
  • Shortly after the antenna was assembled for the first time I had a good VO-52 pass where I heard many EU stations up to S8 on my FT-817.
  • Before the pass was over FO-29 came within range in a very low pass (maximum elevation below 5 deg). Nonetheless I heard K3SZH working EU stations. Wow!
  • Later that day I had a good AO-27 pass with strong signals. I heard many voice contacts in the beginning of the pass until some packet came on and killed them all (don’t know if it was telemetry (see the video below).
  • The overall construction of the antenna looks very good. I would certainly place it in the high quality end of the scale. I was also happy about the packaging; The boom, the 2m elements and the 70cm elements were in three separate plastic bags.
  • Each element has a red end cap on each end that makes the antenna look good 🙂

So, yes, all in all I am very impressed with the Arrow antenna so far. Next step is to set up my FT-817 to transmit and try to have some contacts. More on that later!


Watch in full resolution.

Apollo 11 Anniversary Event on AO-51

On July 20, AMSAT will mark the 40th anniversary of the first manned lunar landing with a special event on the AO-51 amateur radio satellite. During evening passes in the U.S. and Europe, AO-51 will transmit a message commemorating the event. The message will be transmitted on the 435.300 MHz FM downlink and will contain a Robot 36 SSTV image as well as a voice message. It is often possible to receive AO-51 with a simple NFM capable receiver + rubber-ducky antenna and you can use this online prediction tool to find out when AO-51 passes will occur at your location.

Apollo 11 photo

Source: July 2009 AO-51 Schedule

Gpredict 1.0 beta 5 released

Ten days after the release of Gpredict 1.0 beta 4 we are now ready with a new release that fixes some minor bugs in the radio controller.

The significant changes in this release:

  • Fixed some bugs that caused the Doppler shift to be calculated incorrectly in some cases.
  • Fixed a bug that could cause the transponder frequency to “drift” away from the set frequencies.
  • Added new transponder files received from David VK5DG.
  • Minor enhancements in the user manual.

You can download the source code from the project page on SourceForge. Try it, test it, discuss it, and report the bugs you encounter!

 

Gpredict 1.0 beta 2 released

Finally, the Gpredict 1.0 beta 2 release has come together, featuring a completely rewritten radio controller / Doppler tuning algorithm. It became a bit more complicated than I originally anticipated, because the incoming requests for improvement of the original controller did not limit themselves to controlling the downlink and the uplink, but also called for using two different radios.

Given that there are very few full-duplex radios out there designed for satellite communications and that they are very expensive, I found this request to be very reasonable and decided to implement it. The resulting controller should be able to work using receivers, transmitters, half-duplex transceivers, and combination of those. Full-duplex has not been implemented, because I am not sure whether hamlib is able to do that properly. That will be implemented in one of the upcoming betas.

The new radio controller
The new radio control UI. See more screenshots.

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