Category: Electronics

Electronics Projects (by )

So, my electronics workbench is a mess.

This is abundantly clear in the picture from my blog post on redesigning my workspace; the awkward layout is certainly part of the problem, but a deeper problem is that I don't do many electronics projects. So this big workbench is rarely used for its intended purpose, and thus accumulates junk, and thus isn't very inviting to start projects at, which adds to the fact that I'm a bit edgy about STARTING electronics projects, and a vicious cycle has set in...

The only electronic projects I did lately were the 12 volt DC power distribution system for the van and a 9:1 impedance transformer, but those were mainly mechanical builds; the electronics were trivial.

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Amateur Radio Law (by )

The radio spectrum is heavily regulated worldwide. This is because some uses of radio are matters of life and death - communications between ambulances and fire engines, air traffic control, radio navigation, GPS, distress calls from ships, military operations, aircraft/shipping radar, that sort of thing. It's easy to interfere with radio services by just happening to transmit radio waves at the frequency they're using - even accidentally, by a tuning mistake or a poor-quality transmitter that leaks energy at random frequencies - so there's a bunch of laws regulating radio transmitters in every country.

Basically, they trade off various freedoms. Operating a radio transmitter can generally be done using one of three legal approaches:

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Pictures from Space (by )

So the International Space Station (ISS) contains some equipment that's part of a project called ARISS, or Amateur Radio on the ISS.

One of the ARISS projects is occasional transmissions of images via SSTV, or Slow-scan television - basically colour faxes sent via radio.

Anyway, a few days ago, I saw that there was an SSTV transmission scheduled, and the ISS would be passing over England at times I would be able to try and pick it up, so I gave it a go... Read more »

A keyboard design (by )

Ok, so a friend of mine is making himself a custom keyboard - there's a whole hobbyist community of people who design their own, often based on a published design like the Ergodox.

This is related to something I've long wanted to do, which is to obtain myself a chorded keyboard. So I thought I'd write up my current thoughts on the matter, given that they've been brought to the forefront of my mind again!

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Debugging poor home wifi at the Snell-Pym residence (by )

So, we have a fairly complicated network at home - the Snell-Pym Family Mainframe has a dedicated DSL link with a static IP for hosting various Internet-facing things, as well as providing internal services to the home LAN. The home LAN has the usual mix of desktop computers, the laser printer, and two wireless APs for mobile devices to connect to - one in the house and one in the workshop, because one can't get a good signal to both locations. And there's a separate infrastructure LAN for systems control and monitoring.

Now, we've often had on-and-off poor connectivity on the wifi in the house; this used to happen sporadically, usually for around a day, then just get better. The wifi signal strength would remain good, but packet loss was high (10-20%) so stuff just didn't work very well. TCP is poor at high packet loss; it's OK once a connection is open, but packet loss during the initial SYN/SYNACK/ACK handshake causes it to take a long time to retry on most implementations.

I went looking for interfering networks (we live in a pretty wifi-dense urban area) using an app called "Wifi Analyzer" on my Android phone, and it showed a strange network, always on the same channel as the house wifi (as in, if I changed the channel, it would move too). The network never had a name, and the signal strength was about the same as the house wifi; sometimes a bit stronger, sometimes a bit weaker. Read more »

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