When you are in the middle of the desert, pretty much every solution to a mechanical or electrical problem is a hack. [Sgt.M] who was deployed in Iraq sought out the help of radio guru [H.P. Friedrichs] about a static problem he was having. When dust storms would blow in strange things would happen in camp. Humming and crackling could be heard and [Sgt. M] actually had an electrical arc from a lamp to his hand at a distance of about 2 feet.
[Friedrichs] helped him find the problem. Their antennae were acting as static electricity collectors in the dust. All that dust friction in the dry air constantly built up a charge. The solution was simple, discharge the electricity at the antenna when it isn’t in use. Several solutions are outlined on the page, so check them out.
[HP Friedrichs] sent us this cool writeup on how to use scrapped Vacuum Fluorescent Display tubes as amplifiers. For those unfamiliar, a VFD is a display device common to electronics. Many have been replaced by LCD, but you can still find them in modern products. [Friedrichs] points out that his 2008 ford has a VFD for the multimedia display.
Since these units are basically tubes, he figured that you should be able to use them as a tube amp. After some testing, he found it to be quite adequate. The project includes tons of background information on how tubes work, how VFDs work and how to utilize it for amplification. In the picture above, you can see him using one (middle) to amplify a home made radio (right).
I received some good stuff via the tips line while I’ve been making an extra stop after Shmoocon. I spent the day helping my less project endowed family run some new wiring (and made some awesome sparks in the process.)
[Damian] sent in his customized version of the classic Atari 2600 adventure game.
[iraqiGeek] sent in his efforts to use the six-axis controller. He used lib-usb and PPJoy to create his own app.
[HP Friedrichs] sent in this interesting post on building military style power supplies. Good stuff if you’re into building your own gear and like interesting chassis designs.
[John] sent in his version of the new KITT’s light bar. (You know you watched it.)
Got something good to share? Use the tips line.
[H.P. Friedrichs] sent in his Sanfordyne project a while back, but It took me a while to appreciate the effort he put in. (Partly because the write up is so long – but thorough) Grab some of your favorite caffeine supplement and take your time reading over the details. Most of the parts were scavenged, and he mechanically etched the pc board with a dremel tool.
Pete (AC7ZL) wrote in to tell us about his latest project: building a flat response microphone and channel amplifier. You may remember his previous project: building a crystal radio from modern junk. Sounds are “colored” by their surroundings; things like furniture, wall coverings, drapes and building materials all affect the way something sounds. To measure the effect that a space has on sound you need a microphone with a flat frequency response. The core element of Pete’s mic is a modified Panasonic WM61A condenser capsule. He rewired it so that it had a broader dynamic range and could handle a higher SPL at the cost of reduced gain. To boost the signal to a usable level he built a preamp with three stages of amplification. He’s got schematics and a more detailed description on the site.
Continue reading “Flat response microphone and amplifier”
[h. p. friedrichs] (AC7ZL) has some great plans for building a crystal radio. The stator coil and output coil are wrapped around the outside of a CDR sleeve. The tuning capacitor is constructed by sandwich two clear CDs between metal and attaching this inside the top of the sleeve. The rotor shaft is mounted using the bushings from a pair of disassembled potentiometers. A hot needle is used to tap the stator coil through the housing every fifth turn. Even though the parts aren’t very traditional it looks like a really solid radio. He’s got instructions for building a matching ear piece out of tea tins too.
Continue reading “Crystal radio built from modern junk”