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Here's a photo of my cubesat ground station ;-)

Most cubesats up there transmit telemetry via Morse code on UHF, up around 435MHz. With a simple homebrew 4-element Yagi and a cheap multi-mode HT (it can receive SSB, but only transmits on FM) I can pick up the signals from any cubesats that go past.

The stack of Zip disks is an accurate (to a couple of mm) representation of the size of a cubesat. Yes, really. That's what I'm listening to, at somewhere around 1000km away. When the cubesat is launched from its tube, a little springy wire aerial about the size of one of the elements on the Yagi (about 15cm) pops out.

It's not a hell of a lot bigger than the radio in the picture, is it? You could toss one of those out of the ISS with the PTT button taped down, and expect to hear it for a day or so.

The whole point of an SDR is that it is inherently a "real-time spectrum analyser". You snarf down a large chunk of band, do an FFT on it, and display the spectrum.

Take a look at this screenshot showing a 48kHz-wide chunk of the 40m amateur band. It's only limited to 48kHz because that's the rate I was sampling at. I could go wider by sampling at a higher rate, or I could "fake" it by using the same technique that "conventional" spectrum analysers do by tuning the centre spot up and down.

Maplin are pretty crap compared to what they used to be like. They used to have thick catalogues full of all kinds of bits - not just electronic components but servos, motors, gearboxes and bits for building organs and synthesizers like keyboard assemblies, leslie speakers and even flat-pack wooden cabinets. The catalogue often had a page or so devoted to a particular IC (three or four pages, for the ubiquitous AY-3-891x family) showing example circuits and technical information.

If that wasn't enough, they had really cool pictures of spaceships on the cover. Even their adverts had cool artwork.
Here's one featuring one of the spaceship covers, and just look at all the fun toys in this one!

Maplin are pretty crap compared to what they used to be like. They used to have thick catalogues full of all kinds of bits - not just electronic components but servos, motors, gearboxes and bits for building organs and synthesizers like keyboard assemblies, leslie speakers and even flat-pack wooden cabinets. The catalogue often had a page or so devoted to a particular IC (three or four pages, for the ubiquitous AY-3-891x family) showing example circuits and technical information.

If that wasn't enough, they had really cool pictures of spaceships on the cover. Even their adverts had cool artwork.
Here's one featuring one of the spaceship covers, and just look at all the fun toys in this one!

Just as a comparison, the capacitor in this image is about 0.75x0.75x1mm - and I really only use the USB microscope if I need a photograph of the board to show any water damage or anything like that. The transistor below it is about the same size as this camera. I don't even use a magnifier for parts that large.

There are some SMT parts that actually *are* the size of a grain of salt. I *do* use a magnifier for those.

With Arduino, you are left with IDE that lets you do ONLY the basics.

The IDE just wraps avr-gcc and friends, though. So if you find the clever boilerplate that hides a lot of the messy set-up-the-chip code from you starts to trip you up, you can use whatever else you like. There's a project called arscons that gives you an SConstruct file to build your Arduino projects using the standard Arduino libraries if you don't want the Java-based IDE but you want sketch compatibility.

As for "only the basics", I've implemented four-operator FM synthesis, and two-op synthesis with sample playback just using the normal Arduino IDE and a Duemilenove.

That's the problem, the CW test isn't really as relevant but there *should* be a section on using digital modes like PSK. Then we wouldn't have twats like this

73s de MM0YEQ

Actually the bandwidth is 3.1kHz, running from 300Hz to 3.4kHz. This is the range of frequencies that conveys the most information relevant to intelligibility. Anything else makes it easier to recognise the speaker but doesn't make it easier to understand them and can make it harder to understand in noisy environments.

If you low-pass filter speech below 3.4kHz then mostly you only lose the high frequencies in sibilants, but you also filter out a lot of background noise. If you're really interested you could set up a media player to play recorded speech through a tunable bandpass filter and see what you can filter out before the speech becomes hard to understand. Once you've got a feel for how the filters affect the intelligibility, try playing it back in a noisy environment (or mix in a recording of the inside of a car or something).

The 300-3400Hz filter is pretty standard in communications, and it crops up in all sorts of places. I wrote a software-defined radio app that defaults to 300-3400 but is easily tunable up to 15kHz for either low or highpass (although if you highpass filter at 15kHz you won't hear much). Occasionally I'll use it to roll off above about 2.8kHz to remove high-pitched squeaky noises from adjacent transmitters.

Obligatory screenshot: http://www.gjcp.net/~gordonjcp/lysdr.jpg

You can see the yellow strip representing the passband of the filter. The (fairly weak) signal shown doesn't really have any strong components much above about 2kHz, and I could reduce the noise by sliding the leftmost (lowpass) filter in a bit. A quick explanation of what you're looking at - that's a spectrum plot of a chunk of the 7MHz amateur band, with lower frequencies on the left as indicated by the scale at the bottom. Since on 7MHz we use lower sideband (LSB), the higher audio frequencies correspond to lower RF frequencies (further away from the red tuning cursor).

Fabric.

http://www.gjcp.net/articles/fabric/

Saves so much hassle and buggering about.

Right, want more? Okay:

Screenshot of gpredict showing two items - the first item (2009-004a) appears to be the satellite, the second doesn't seem to transmit on any frequency I've listened on.

Audio recording of what is presumably telemetry from the satellite, received on about 465.0125MHz (allowing for a bit of Doppler shift). The quality is rubbish because I was trying to hold the antenna, hold my laptop and tune the radio all at the same time.

Right, want more? Okay:

Screenshot of gpredict showing two items - the first item (2009-004a) appears to be the satellite, the second doesn't seem to transmit on any frequency I've listened on.

Audio recording of what is presumably telemetry from the satellite, received on about 465.0125MHz (allowing for a bit of Doppler shift). The quality is rubbish because I was trying to hold the antenna, hold my laptop and tune the radio all at the same time.

Glad you find it easy to build a radio powerful enough to talk to the space station. Where is the news article about you? Because if 4 college students can get this kind of attention for doing something that has been done before, and building a radio was too hard for them... then you should be all over the news considering your skills are greater than theirs, and thus you must have accomplished more than they have.

It's easier to just walk into a shop and buy one for £140. I built the aerial that I use to communicate with the ISS, that took about an hour. Frankly I'd be embarrassed if there was a news article about it - I point an aerial at the right part of the sky, at the right time, and I can talk to people on the ISS. Lots of people do it, every day. Part of the requirement for having an amateur radio licence is knowing how to set something like this up.

Here are some pictures sent from the ISS, received at my house, from when Richard Garriot was up there.

Yep, calling on the downlink isn't going to work, and will just annoy local amateurs. Plus you'll be stomped on by someone 200 miles higher than you.
I think it was a bit silly wasting time sending dull (IMO) SSTV images back when Richard could have been QSOing with thousands of amateurs worldwide. He was up there for 10? days, and probably had lots of time spare (as he wasn't part of the crew). The image equipment can be left there, switched on at any time.
Receiving an image is a one-way communication, and (for me) it's the 2-way aspect that rocks. You can hear astronauts - but you can (try to) talk to them too.

That MP3 of the school contact is pretty cool - it's the same one I heard and got the two short vids on my site of. I'd have been sooo excited if I could have spoken to an astronaut when I was at school :) Do you mind if I link to/mirror your copy from my page?

I heard him. I also received some of his SSTV pics. Unfortunately I was at work, so I couldn't call him myself. There was one local-ish guy calling him on the downlink frequency, which really isn't going to work.

Pics (and audio) from space here: http://www.gjcp.net/space/

Just to reply to myself - here's an SSTV image received with a simple J-pole antenna and a 20-year-old mobile transceiver!

http://www.gjcp.net/~gordonjcp/na1ss.jpg

Even with the ISS at 25 degrees elevation, it was a very very strong signal.

You could probably do something loop-based by loading loops into a soundfont, and using fluidsynth and a sequencer like seq24.

You might want to look at DSSI, the Disposable Soft Synth Interface, which is kind of the Linux version of VST. It doesn't do quite as much as VST does but the programming interface is not quite as Byzantine and perverse.

Shameless plug: I've written a couple of DSSI synths, based on Xsynth-DSSI. One is a kind of wavetable synth, and one is a TB303-style monosynth. You can get them at http://www.gjcp.net/wsynth.html - try them and send me any suggestions or comments. Yes, I know the web page looks crap.

It doesn't open in a new tab, but the current tab (as you'd expect).

Have a look at this error screen for an example. I'm on XP at work, but I would think that other platforms would be similar.

As of glenebob's comments, I now know of two manufacturers that did that - didn't know that Subaru used the same thing. I guess the Subaru Impreza really is the Citroën GSA of the 21st century (2 litre liquid cooled flat four, instead of an 1300cc aircooled flat four, four wheel drive instead of front wheel drive, but other than that...)

Your Ford Focus has a rev limiter to stop you spinning it up to the point where its shitty Pinto-derived engine, original design dating back to crappy American cars from the 1970s, drops its guts in an embarrassing oily mess. Just 'cos I can rev my 1978 Citroen GSA to 9600rpm, doesn't mean you '04 Ford will even get halfway there...

I have actually repaird a quad bike where the rear axle was so fouled up with gunk and baler twine that I had to chisel my way through to the hub nuts, cut them off, draw the hubs off the axle, and then cut the studs off the hub to get the wheels off...

And my old Citroen GSA, with its *huge* hubs (three studs on about a 9" spacing) and inboard brakes - often it's as easy just to undo the hub nut and pull the hub, wheel and all. There's no brake disc or caliper out at the wheel, which frightens the spotty 16-year-olds at the local Kwik-Fsck tyre and exhaust cheap-o-rama.

It's not cheap to run - it needs 5 litres of synthetic oil and a filter every 5,000 miles, but that's the price you pay for an air-cooled engine that revs to 7,000rpm. The oil works very hard - it's not just lubrication, it's important for cooling too.

It's probably the best car I've ever driven. It certainly outhandles everything short of top-of-the-range sports cars, but without the horrible harsh "sports" suspension. And it goes through snow better than any 4x4 (little skinny tyres, just stick knobbly snow tyres on and raise the suspension up a notch). I wish Citroen still built something like them.

I've actually done this with eight LEDs (four red, four green) and the parallel port on my firewall machine. I did it mostly because it had a cool smoked perspex cover that slides over the drive bays, and the LEDs shining through it looks pretty cool. Especially when you make them flash and do stuff. Have a look at some pics.

In this case, the LEDs have their anodes connected together, and brought back to the 5v rail, and their cathodes connected to the parallel port pins through 220 ohm resistors. You then bring the appropriate pin low to turn the LED on. There's a good reason for doing it "backwards" - the gates driving the parallel port can sink more current than they can source. That is to say, the transistor pulling the pin to ground is "stronger" than the one pulling it to +5v, so it's more suitable for turning on an LED. You could use two resistors and a small transistor per pin, too. If you like.

Yes, my Scimitar is looking a bit scruffy in that photo. That's a "before" photo, you can see the "after" photo when it's been sprayed.

Another ultimate tinkerer's vehicle is the Landrover. It's just a big Meccano set.

Oh, and let's not forget the venerable Volvo 340 (shown here inspecting the runway of a small airfield in the north of Scotland, hence the orange beacon) which is almost as easy to take to bits entirely. 0-100mph in about 30 seconds, though. Tops out at 115 mph, of which 3 miles will be used getting up to speed and the rest will be absolutely terrifying.

I suspect they're looking for technology-laden cars though. In which case, if you want something cheap, fun, and very cool, get yourself a Citroen XM. Mine was a fairly basic-spec one, with no aircon or ABS, but still managed to have about 6 ECUs dotted about (three in a big "avionics bay" under the bonnet. Lovely, comfortable, smooth ride thanks to its hydraulic suspension, which stiffens up when you drive fast or go round sharp corners. For a good example, watch the film "Ronin" - in the car chase, look at how the Audi A8 fishtails and slides everywhere, and the XM only slides on loose gravel. And then, only a little bit...

Another ultimate tinkerer's vehicle is the Landrover. It's just a big Meccano set.

Oh, and let's not forget the venerable Volvo 340 (shown here inspecting the runway of a small airfield in the north of Scotland, hence the orange beacon) which is almost as easy to take to bits entirely. 0-100mph in about 30 seconds, though. Tops out at 115 mph, of which 3 miles will be used getting up to speed and the rest will be absolutely terrifying.

I suspect they're looking for technology-laden cars though. In which case, if you want something cheap, fun, and very cool, get yourself a Citroen XM. Mine was a fairly basic-spec one, with no aircon or ABS, but still managed to have about 6 ECUs dotted about (three in a big "avionics bay" under the bonnet. Lovely, comfortable, smooth ride thanks to its hydraulic suspension, which stiffens up when you drive fast or go round sharp corners. For a good example, watch the film "Ronin" - in the car chase, look at how the Audi A8 fishtails and slides everywhere, and the XM only slides on loose gravel. And then, only a little bit...

Another ultimate tinkerer's vehicle is the Landrover. It's just a big Meccano set.

Oh, and let's not forget the venerable Volvo 340 (shown here inspecting the runway of a small airfield in the north of Scotland, hence the orange beacon) which is almost as easy to take to bits entirely. 0-100mph in about 30 seconds, though. Tops out at 115 mph, of which 3 miles will be used getting up to speed and the rest will be absolutely terrifying.

I suspect they're looking for technology-laden cars though. In which case, if you want something cheap, fun, and very cool, get yourself a Citroen XM. Mine was a fairly basic-spec one, with no aircon or ABS, but still managed to have about 6 ECUs dotted about (three in a big "avionics bay" under the bonnet. Lovely, comfortable, smooth ride thanks to its hydraulic suspension, which stiffens up when you drive fast or go round sharp corners. For a good example, watch the film "Ronin" - in the car chase, look at how the Audi A8 fishtails and slides everywhere, and the XM only slides on loose gravel. And then, only a little bit...