Category Archives: Amateur Radio

iHAB Iowa High Altitude Balloon

I was on the #hamradio channel on IRC this morning where people were watghing the progress of the Iowa High Altitude Ballon (IHAB) operating with callsign W0OTM-4. We saw it drift up to an altitude of about 88K feet, before descending. They had a 20m beacon, an APRS beacon running on 2m, and a cellular telephone tracker. Very cool. Hopefully, they’ll have some photos soon.

iHAB Iowa High Altitude Balloon.

Addendum: Using aprs, i tracked both the balloon and the chase vehicle (callsign W0OTM-2) and showed the complete groundtrack of both. Pretty neat.

Red track is the balloon, Blue is the chase vehicle

Morning Commute with OpenTracker+

So, this morning I decided to give my OpenTracker another run, both to get a feel for how some of the parameters worked, as well as just trying to find out how complete the coverage is here in the Bay Area.

For this test, I first modified the APRS symbol to stop being the balloon that I had yesterday (symbol “/O”) and switched it instead to the car icon (symbol “/>”). I also turned on “smartbeaconing”, (described here) so that it would beacon more frequently as my speed increases, and also beacon when I made turns of more than 28 degrees. I then embarked upon my commute. It worked pretty well, with a few caveats.

On the main highway, coverage was in general excellent, but in the areas directly surrounding my home (which has quite a few hills) the coverage is much spottier. Even where coverage is good, most of the digipeaters here me are across the bay on San Francisco peninsula or are north, with distances that are quite large (and perhaps surprising, given the fact that I am transmitting with only 5w of output power). I’m wondering, is there some way to locate all the digipeaters that are active in a given geographic region? I’m interested in terms of my balloon planning: while I am going to be carrying an APRS equipped mobile rig in the chase vehicle, it would also be nice to know that our data has a good chance of making it to the APRS-IS network so that people could track it over the Internet, and to serve as a backup for our mobile operations.

Anyway… more on it all later.

A Project from the Past: My OpenTracker+

Over a year ago, I blogged that I had assembled a bit of amateur radio gear, the OpenTracker+. This little gadget has a couple of DB-9 ports on it. The first is used to connect to a GPS, and the other to a radio, such as my Kenwood TH-D7A. Together, they form a tracker: the gps provides positioning, which the OT1+ encodes into a packet radio signal and sends via the HT.

Back then, I had it roughly hooked to my Garmin GPS 18 LVC, but I didn’t do a lot of testing with it (I didn’t wire up the proper power supply cabling and the like), but lately I’m trying to get back onto the possibility of doing a high altitude balloon launch, so I dusted it off and decided to get it all working again. Since I built it, Argent Data Systems has begun to sell a nice little compact GPS, the ADS-GM1, which simply plugs into the open tracker, so I went ahead and ordered one, along with the radio/power cable designed to work with my Kenwood HT. I don’t really think that I am going to send this precise hardware into space (it’s rather bulky compared to what can be achieved now) but it will give me experience with the OpenTracker, which has a smaller SMT based version that I could use.

Stay tuned for some smoke testing later.

Addendum: It works! I hooked it up to my TH-D7A, and drove it around for bit. I didn’t bother to calibrate the audio levels very well, but it seems like it works pretty well. Here is a log of the packets received at findu.com for K6HX-9. The voltage varies as I start and stop my car, while the temperature (23C, or about 73F) stays pretty constant (it was a nice day today).

K6HX-9 on a trip to the frozen yogurt shop via my OpenTracker+

Pictures of the Blum Blum Shub Random number generator…

A couple of years ago, I did a post about the Blum Blum Shub random number generator. I was watching Psych, and bored, so I decided to just make a picture of the random bits generated when I generated two 50 digit primes. Without further ado, or explanation, check it:

There do indeed seem to be very little pattern in it. Although if you knew the two primes that I used, you could generate the value of not just any bit here, but any bit in the future too.

Time for bed.

Anybody want to take over the domain telescopemaking.org?

I’ve had the domain telescopemaking.org for a long time (even longer than brainwagon.org) but I haven’t been keeping up with refreshing any of the content on it in years. Rather than just continuing to maintain the aging content, I’d like to pass the domain off to someone who might make better use of it. Are any of my readers interested?

Ed Felton on How Not to Fix Soccer

I’m not much of a soccer fan, or even a football or basketball fan anymore. If I am passionate about any sport, it would have to be baseball. But Ed Felton has a rather nice essay about not just why soccer is the way it is, but why any tweaking of the rules to more suit American audiences isn’t a very good idea. I think to a certain degree, the arguments also apply toward baseball. It’s worth noting that both soccer and baseball predate any kind of cheaply available timekeeping technology. This has probably a lot to do with why the rules are the way they are, and why soccer in particular might be enjoyed in far flung parts of the developing world.

How Not to Fix Soccer | Freedom to Tinker.

From my home office: first picture through my microscope

As you might have guessed, I’m a “collector”. Not of anything in particular, but of anything that interests me even vaguely. A few years ago, I bought an old Zeiss Jena laboratory microscope at a swap meet for (if memory serves) around $50. It’s a very nice, heavy microscope and included a pair of Zeiss eyepieces (7x and 10x) and a pair of objectives (10x and 40x). I hadn’t done much with it, but recently I’ve begun to think of fun things that I might do with it, so I dusted it off. Of course, to share pictures of what I see, I’d need to be able to take a photograph through it, so the first order of the day would be to see what I could do with my little Canon SD1100 (a small point-and-shoot camera). Since I didn’t have any microscope slides, I just clamped a dollar bill onto the stage. I installed the 10x objective with a 7x eyepiece, roughly aimed an led flashlight at the mirror, and clicked this picture:

A dollar bill, at 70x...

Not bad at all. The image isn’t very well focused because, well, it isn’t very well focused, and because the dollar wasn’t clamped flat, so bits of it are in focus and out of focus, but it’s very promising. I need to setup a good light source and get some slides. Stay tuned, I have something in mind.

Addendum: I found a plastic container that had some small writing on it, which was a tiny bit flatter and setup my camera. I tried zooming in to get rid of the round vignette around the image, and shot these two pictures. Looks like this will work just great. I need to mock up a little mount to hold the camera, and work on getting a better light source, and then some slides and cover slips (already on order) and then… some slightly more interesting pictures hopefully.

Half zoomed...

3x zoom (full)

From the code cellar: a program to find haiku in text…

While I was surfing around this weekend, I was reminded of the old sweetcode.org website (sadly, which is no more, but you can still see courtesy of the Internet Wayback machine if you like) and found an old chunk of code that I had archived that was written by Danny O’Brien based upon an idea by Don Marti. It basically would scan a text, break it into syllables, and then output any haikus (segments of text that have the 5-7-5 syllable counts). The program further allows you to specify that the haiku should start with a capital letter, and end with a period.

It was a bit broken, but a few minutes of hacking got it working again, and I fed it one of my favorites: The Adventures of Sherlock Holmes. Here is a smattering of some of the better ones it found.

He never spoke of
the softer passions, save with
a gibe and a sneer.

You understand? I
am to be neutral? To
do nothing whatever.

She knows that the King
is capable of having
her waylaid and searched.

But then, when I found
how I had betrayed myself
I began to think.

Some letters get more
worn than others, and some wear
only on one side.

I can stand this strain
no longer; I shall go mad
if it continues.

Twice he struck at the
chamber door without any
reply from within.

He put out his hand
and coldly grasped that which she
extended to him.

It is all dark to
me. But perhaps it may grow
lighter as we go.

I’m not sure why I find these so amusing.

Maidenhead Grid, courtesy of geolocation in HTML5

What it looks like on the iPhone...

If you have a browser that supports the HTML5 geolocation facilities (such as Mobile Safari on the iPhone, or certain recent versions of Firefox) then you can try clicking on the following link to find out your Maidenhead grid square. It may not remain there forever, since it is just hosted on my machine, but it should work reasonably well. At the right is a picture of what it looks like on my iPhone.

Grid Square

If you are using Firefox, the accuracy might be good, or might be bad. It really depends on how effective Google’s IP based geolocation is in your area. At my brother’s house in Hillsboro, OR (near the Intel Campus) it was very, very accurate. Of course, if you are using the iPhone, it uses the built-in GPS. Feel free to swipe this idea and use it however you see fit.

If you find this useful, please let me know, and I’ll consider making a more permanent home for it. I’d also welcome any other suggestions on things that might make it more useful.

Addendum: I made some improvements (notably, to also give the accuracy of the measurement, and added a small google maps display) and IRC #hamradio buddy autojack confirmed that it works on his Android phone, and thoughtfully provided a couple of screenshots.



The WebM Project : Welcome to the WebM Project

While I am surfing around, I discovered that Google made good on their promise to release the VP8 codec they obtained from their acquisition of On2 earlier this year as a royalty-free open alternative to other video codecs. This isn’t of much use right now to end users, but hopefully this will result in a more ubiquitous and portable web video standard.

The WebM Project : Welcome to the WebM Project.

On G4ILO’s Scratching the SDR itch

I try to surf a lot of different ham radio blogs, mostly for inspiration about projects. My own life has been a bit hectic lately, and isn’t really likely to calm down until summer is well underway, but I am still reading. Today’s posting was inspired by a posting over on G4ILO’s blog:

G4ILO’s Blog: Scratching the SDR itch.

Surf on over and read, then come back. Please, come back.

I empathize with the opinions to a large degree, but overall I can’t help but think that it’s a very “doom-n-gloom” viewpoint that requires some criticism to put it in perspective.

First of all, I think it’s important to understand that for at least the last twenty years, computers and software has been a part of radio. Sure, mostly they have just monitored buttons and updated displays, but increasingly they provide sophisticated filtering and signal processing that would be difficult, costly or simply impossible to provide any other way. Software-defined radios are merely the next logical step in a continuum of software design in radio. And just like we aren’t going back to spark or tubes, we are aren’t going back to radios without microprocessors in them: they are just too cheap and too useful.

When Julian says that “general purpose computers are just too much hassle”, he’s probably right, but that isn’t an indictment of software defined radio so much as a indictment of the means by which we currently consume it: namely by using an operating system which wasn’t very well designed for the purpose that we have co-opted it for. Let’s face it: 99% of the annoyance of current SDR stuff is related to sound card issues, and that’s mostly because Windows (doesn’t matter what version) basically sucks for sound handling. Each card implements a different set of controls which can’t be reliably configured for a dedicated application.

But there is more than just sound cards: Windows isn’t very well suited to the creation of interactive interfaces. Yes, using drop downs and mouse is annoying compared to just turning knobs. But that’s not to say that better interfaces can’t exist. And, in fact, there is considerable reason to believe that once you involve software, better interfaces can exist. Being able to display 200khz or more of spectrum, and select individual signals just by pointing is a blast. Being able to design bandpass or notch filters by drawing or adjusting the filter responses interactively is great. Being able to configure soft buttons to switch settings for different monitoring tasks is cool.

Lastly, when Julian says “With real radios you can look at the schematic and get in there with your soldering iron and make modifications and or fix faults”, but that somehow that isn’t possible with SDR, it’s mainly a matter of perspective. Modifying software isn’t particularly any more difficult than modifying hardware: in fact, the nice thing about software is that it is usually easier and less expensive to distribute your changes. Understanding how to use an FFT or frequency shift and filter signals isn’t really that much harder to understand than (say) the details of how a Gilbert Cell mixer works. It’s just a different set of skills, one that we can nurture or not as we see fit.

I want to see more rigs which provide generic USB interfaces for sound and serial control (or if you need the bandwidth, how ’bout gigabit ethernet?). I’d love to have a radio with all the normal front end, but when I plug it into my computer, wide band sound data is available via USB and a serial tty port becomes available on my Windows, Mac OS or Linux box. It’s totally doable, and would allow us the best of both worlds.

I have an SDR-IQ, and it’s a nifty little gadget (although does require special driver support, which is a teensy bit annoying, although the drivers do exist on Windows and Linux). It literally is a black box, with a USB cable and an antenna port, and a single LED. It’s incredibly versatile, and one of the principle uses they have for them is to provide an wideband panadapter interface at the IF of conventional HF rigs. There is no reason that it has to be a separate box: it could be built into more conventional rigs.

I for one embrace our increasingly software defined future, and the new era of experimentation that it will bring. I think the real challenge will be to either acquire the necessary skills and imagination to create the applications that we all want, or to at least encourage a generation of younger software engineers to invest the time to do it.