Graduate student Jason Ahrns captured a stunning image of red sprites over Nebraska while aboard a plane chartered by the National Center for Atmospheric Research. And behold Scott McPartland's rare video of the phenomenon in May. (more…)
During experiments with digital voice mode in hamradio I discovered a nice project describing an adapter for D-Star, DMR and other digital modes based on an Arduino Due and a little PCB to be put on top. This unit is called the Multimode Digital Voice Modem or MMDVM (see ). It seems that this is getting quite popular because hard- and software is Open Source.
Here is the die photo: super tiny. I bet they get thousands of dice off of each wafer. Looks like it’s a protocol called MIFARE. Vendor of the chips is NXP. I think it’s their ultra light family
The amazing bit is that a card is printed with conductive ink, a semiconductor added (with a transistor count in the tens of thousands), a vendor-specific ID placed on the outside with another layer of paper, spooled in to giant rolls, vended for a single trip and then thrown away…..
This is my new hybrid guitar tube amp which utilizes a solid-state input stage, DSP reverb, and solid-state phase splitter. Only the push pull, class AB output stage utilizes tubes, namely two EL84’s run at 390 volts with cathode bias. The bias uses two 15 volt zeners which creates a bias current of about 26mA. This requires almost 30 volts of swing on the grids to drive the amp to saturation. This is accomplished with a little switch mode boost converter that generates 29 volts to drive the phase splitter opamps. All of the solid-state circuitry runs off the AC filament supply for the tubes. The solid state portion is basically my stomp amp design( also on this blog) minus the final power amp, which is replaced with the phase splitter.
Interfacing dekatron tubes with a microcontroller is fairly easy, once you understand how the tubes work. Threeneuron’s Pile o’Poo of Obsolete Crap provides the necessary background information and schematics for making this work.
I used two russian OG-4 tubes. I prefer the orange look of the neon tubes rather than the purple look of the argon filled OG-3 tubes. The latter tubes just look to modern for my liking. On the above picture you can see how I have mounted the tubes on a rig alongside two Magic eye tubes.