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!


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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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Gpredict Updates

I just realized that the last time I have blogged about my pet project, Gpredict, was back in February 2007. Back then, the big news was the Sky at a Glance function and there has in fact been a lot of evolution since then despite the big silence in the Gpredict Developer Blog. Let me try to sum up the progress from last two years as well as what you can expect to happen in the weeks to come.

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