Many of us tried the old “Two tin cans connected by a string” experiment as kids. [Michael Rainey, AA1TJ] never quite forgot it. Back in 2009, he built “El Silbo”, a ham radio transmitter powered entirely by his voice. El Silbo is a Double Side Band (DSB) transmitter for 75 meters. While voice is used to excite the transmitter, it doesn’t actually transmit voice. El Silbo is a CW affair, so you should bone up on your Morse Code a bit before building one. Like many QRP transmitters El Silbo’s circuit is rather simple. A junk box loudspeaker is installed at the bottom of the can to convert voice power to electrical power. The signal is passed through a step up transformer, and used to excite a 75m crystal. Two NPN transistors (in this case MPS6521) pass the signal on through a second transformer. The signal is then routed through an LC network to the antenna.
Back in 2009, [Michael] brought El Silbo to the Maine coast in an attempt to make a transatlantic contact. This isn’t as far-fetched as it sounds – [Michael] has “crossed the pond” on less power. While the attempt wasn’t successful, [Michael] has made connections as far as 1486km, or 923 miles. That’s quite a distance for simply yelling into a tin can! One of [Michael’s] favorite El Silbo stories is a 109KM conversation (QSO) he had with W1PID. [Michael] found that the signal was so good, he didn’t have to yell at all. He reduced power by dropping to his normal speaking voice for the “dits and dahs”. The two were able to converse for 17 minutes with [Michael] only using his speaking voice for power. We think this is an amazing achievement, and once more proof that you don’t need a multi-thousand dollar shack to make contacts as a ham.
Continue reading “Amateur Radio Transmits 1000 Miles On Voice Power”
[Bill Meara] has finished up his radio. It both looks and sounds great. It was only a few weeks ago that [Bill] posted a guest rant here on Hackaday. The Radio he mentioned building in the rant is now complete. The transceiver itself is a BITX, a 14MHz Single Sideband (SSB) radio designed by Ashhar Farhan VU2ESE. Ashhar designed the BITX as a cheap to build, and easy to tune up transceiver for radio amateurs in India.
By utilizing parts easily sourced from scrapped TV sets, the BITX can be built for less than 300 Indian Rupee – or about $4.70 USD. In [Bill]’s own words, “Five bucks and some sweat equity gets you a device capable of worldwide communication.” He’s not kidding either. [Bill’s] first QSO was with a ham in the Azores Islands of Portugal.
[Bill] built his radio using the “Manhattan” building style, which we’ve seen before. Manhattan style uses rectangular pads glued down onto a copper ground plane. It makes for a more flexible design than regular old dead bug style building. Looking at all those components may be a bit daunting at first, but plenty of support is available. [Bill] has an 18 part build log on the soldersmoke website. There also is an active yahoo group dedicated to the BITX.
This applies more to older vacuum technology than your average solid state hardware, but [Richard] put together an interesting project. It’s designed to test a component for its breakdown voltage without destroying it. The general idea of the ‘BVT’ is to increase the voltage applied to a device until some current leakage is detected. Of course, any device that includes notes on probable arc length in relation to kilovolts is awesome by definition.