24 April, 2012

Incredible projects based on 7400 logic

Last fall there was a competition at DangerousPrototypes with many interesting entries based on the 7400 logic gate family. The ancestry of these circuits goes back to the 60's and early 70's, but they are still popular. I have picked out some of the ham radio related entries here.

They said "The  Open 7400 Logic Competition brings awareness to open hardware and software, and fosters understanding of the building blocks of modern integrated circuits. What can you build with logic chips?"

I think the most interesting and inspiring entries were:

22 April, 2012

Simple IKEA transmit indicator

IKEA Oleby automatic wardrobe light with passive
infrared sensor upper right and four LEDs in the center.
Passive Infrared (PIR) detectors have the bad habit of being sensitive to radio frequency (RF) radiation. This can be a nuisance for neighbors of radio amateurs. But we can use this property to our advantage as this makes them suitable for transmit indicators next to a feedline.

The IKEA motion activated LED sensor light, which one can get for a few dollars or euros, turns out to be quite simple to hack for this purpose. You can only buy them in pairs so the other one can be put to use in the darkest wardrobe you have.

09 April, 2012

Whatever happened to the 1 Volt QRP Transceivers?

Output stage of the 1 Volt DL2AVH transmitter
(from http://www.lichtnetzwerk.de/1volttxvr_dkumentation.pdf)
I am intrigued by minimalist transceiver designs like the Pixie 2 which I built some years ago. Therefore the "1 VOLT Challenge" from Dayton 2000 is also something I wish I knew more about. It had these winners:

1. Duncan Walters, G4DFV - The HAMEOBA - A 100 mW Single Cell CW Transceiver (30m)
2. (tied) Helmut Siefert, DL2AVH - A 30m 1V QRP transceiver
2. (tied) Charles Fletcher, G3DXZ - An 80m CW QSK Transceiver
4. Jim Roberts, NC9H - A 20m 1.5V Transceiver

Now, what happened to these designs? I'll try to figure it out from sources on the web.

03 April, 2012

A history lesson from call signs

World empires and colonies in 1914, also at
the time of the 1. Int. Radiotelegraphic Convention.
Source Wikipedia Commons, user Andrew0921
There's a lot of history to read out from amateur radio call signs. Being interested in history as well as amateur radio I found that for some countries you can actually figure out which time period it got independence just by looking at the prefixes of the call sign. But on the other hand the history of the international conferences and the call sign allocations is as complex as politics can be so this short blog post can only scratch the surface of this complicated topic.

I have always been envious of those radio amateurs who have a call sign starting with a letter that reflects their country's name. This seems to be the privilege of big and powerful nations, or countries that were just lucky in having names that didn't overlap too much with those of other nations. Among the 1913 call signs one can find: