Phase 4B Weekly Ground Engineering Report

From Michelle Thompson via the AMSAT North America Facebook group.

So what happened when I finally got to the lab? Well, we able to obtain an example flow graph, with some controversy between installations, for DVB. Here is a DVB S2 transmitter in GNUradio. After some troubleshooting to get it to work with the X310, we saw an output waveform using the built-in instruments in GNUradio. Here’s the list of blocks availabe in mainstream GNUradio for DVB. Isn’t this great? Note that there is already DVB-S2X, although it has not been completely tested due to the lack of receivers. Wouldn’t it be great if we could help out here? Next, we transmitted a test signal. It looked a bit puny at first, but we found the settings for gain and improved performance a bit. In other advancements, the HackRF team submitted their first pull request in their documentation. Here’s an FM receiver implementation based on Michael Ossmann’s wonderful tutorials about using HackRF and GNUradio at 

We tried to receive with DVB-T RTL-SDR dongles, but haven’t quite gotten this to work yet!

If you are anywhere in the ballpark about being interested in SDRs, then watch these videos. If it seems remotely interesting, then consider joining up our team and participating. It’s a lot of fun and we need you.

Here’s the instrumentation of the FM broadcast band experiment. The waterfall shows the stations clearly.

Next up is something I wanted to point out to those of you interested in microwave experimentation. Here’s the band plan for 10GHz. Note that our downlink is in the Space, Earth, and Telecommand sub band. Note that right next door is an analog and digital band, where bandwidths greater than 1Mhz are welcome. That would be us, wearing our terrestrial hats.

We’re looking at making the radio autonomously determine what it’s listening to, and act accordingly. This is a band plan that works to our advantage since we believe we can use the same IF of 700MHz for both modes.

We use Github for all our documentation and software. If you need to learn about github, there are many tutorials at github. You can get off the ground and to the point where you are forking and pulling like a pro. Check it out.

Next up, something totally different. We want the user interface for Phase 4 Ground to be really good. We are visual creatures. One of the projects for visualization of contact history is DynamicQSL. This project is focused on exploring, researching, developing, and publishing an open source application that takes your log of QSOs and produces a beautiful representation of your activity with other stations. If you have only contacted a station once, then the resulting QSL card for you and them is simple. If you have had a lot of contacts, then it’s complex and rich. The inputs to the DynamicQSL are whatever you’ve chosen for your QSL card image, or perhaps your avatar on Phase 4 Ground. So far, it’s clear that automatically generating fractal images is not going to easily work. Choosing a good fractal image requires a human curator to make good art. Using tree diagrams means the card is predictable and boring. However, there’s another way. There’s a wonderful book about algorithmically produced art called Creating Symmetry:
The Artful Mathematics of Wallpaper Patterns by Frank A. Farris. This seems to be a winner. Here’s something I made in a few lines of code using SageMath online. Try out this open source alternative to MATLAB at All the code for the DynamicQSL experiments is in the visualizations directory of the documents repository at Phase 4 Ground’s github site.

I’m hoping to work with Zach Leffke at Virgina Tech to find students with an artistic and programming background to join this project and create a wonderful aspect to our user interface on Phase 4. There is nothing stopping this from being an entirely standalone project that anyone with a QSO log can use. The goal is to feed in a log and have beautiful dynamic cards, possibly animated to show contacts over time, produced so that the operator can display or send them. So Zach, if you’re listening, I will be writing you as soon as I can with a lot more details.

None of this is possible without your support. Please join ARRL and AMSAT if you are not a member already. They make this project possible. If you want to help the project, then join at or contact me directly. You don’t have to be an expert, you just have to want to become one. I will meet you wherever you are, and help you out as best I can. Until next week!