While looking at the hadie high altitude balloon project, I got to thinking about making a microcontroller that could send RTTY. I knew that traditional Baudot (more properly the ITA2 code) was a five bit code with codes designed to switch back and forth between “letters” and “figures”, but I had never looked at the actual matrix. Here is the diagram from Wikipedia:
Tell me, is there ANY rhyme or reason to this layout? It literally looks like they just scattered the letters and numbers onto the codes more or less completely at random.
I was just curious: can anyone tell me what I am missing?
While listening to the Amateur Radio Newsline podcast this week, I was interested to hear that a group of hams from Ireland had launched a balloon which transmitted digital pictures back from the balloon while it was at altitude, using a version of dl-fldigi. While I was familiar with fldigi, I hadn’t heard of this version, so I did a bit of searching on the web.
First of all, you can find details about the hadie high altitude balloon project here:
Hadie High Altitude Balloon Project
The flickr photostream from the most recent flight of hadie:4 can be found here:
Slideshow of hadie:4 images
Sadly, the balloon had a slower than predicted rise rate (2m/s instead of 3.5) and so overshot England after floating across the Irish Sea and landed in the North Sea. But it’s very cool that we got these live photos back.
Digging a bit more revealed this nice project web page which had many details about the hardware and software they used. They used a serial based camera module previously sold by Sparkfun (now apparently retired), an NTX2 module from Radiometrix which broadcasts on 434.075Mhz, and a cpu based upon the ATmega644P chip. The flight software appears to be written in C, and reads the data from a GPS and the camera module, and repackages it in a custom format called ssdv for transmission over 300/600/1200 baud 8 bit RTTY which can then be decoded by a custom version of fldigi known as dl-digi. Very neat. The radio module that they use has an output power of just 10mw, and yet was successfully decoded over distances greater than 500km. What’s kind of cool about this technique as opposed to (say) the analog Robot32 mode that ARISSAT-1 uses is that the image is broken up into packets, which are transmitted and received independently. The dl-fldigi can send any received packets to a central repository, and thus if any station successfully decodes a packet, then the image can be reconstructed (something that is difficult with analog SSTV).
I didn’t have much to add to this, I just wanted to stash this for later. While the images they got don’t really compare to some of the awesome HD footage that we are seeing shot with GoPro cameras, the immediacy of this seems very appealing, and it’s a good technical challenge.
My early success with making tasty no knead bread has sent me off on the Internet looking for additional recipes. As a complete breadmaking newbie, I have a lot to learn, but luckily, there is lots of good websites to help me understand and extend my tiny skills in this vast topic. The best of these that I have found so far is Breadtopia, which has all sorts of great recipes and many cool videos that will take the mystery out of breadmaking. I of course focused on the no knead recipes, which seem the most accessible to me, but apparently Cooks Illustrated extended this recipe in a couple if interesting ways, notably by adding a small amount of vinegar and beer to the dough. They also have an interesting recipe for a sandwich loaf, which has a tighter crumb and thinner crust. I’ll be trying some of this out over the holiday weekend. If you’ve never made bread before (or even if you have), consider trying this stuff!
Cook’s Illustrated Almost No Knead.