Posts Tagged ‘computer’
Anyone looking at my blog could be forgiven for thinking that I had dropped off the face of the earth for a while, has nothing been happening in my world?
Well, the answer is that a LOT has been happening and all at once. My daytime job has become busier and there have been several non-radio projects at home that needed to be completed. All this has kept me away from Amateur Radio blogging even though I have spent more time on the computer than usual.
In between projects I did manage to stumble across this video of Rear Admiral Grace Hopper explaining just how “long” a nano-second is and what it looks like. This has relevance to radio as we’re usually well aware of frequency and wavelength but don’t usually spend too long thinking about speed.
ZL1HIT (Bryan Rentoul) has bridged a gap of more than 80 years by combining the text transmission system developed by Rudolf Hell in the late 1920’s with current microprocessor technology.
|A sample of received Hellschreiber test from Bryan’s beacon|
Hellschreiber sends a line of text as a series of vertical columns. Each column is broken down vertically into a series of pixels, normally using a 7 by 7 pixel grid to represent characters. The data for a line is then sent as a series of on-off signals to the receiver, using a variety of formats depending on the medium, but normally at a rate of 112.5 baud.
This process was historically accomplished with mechanical equipment but there are very few examples of this equipment still in operation and it is now sent and received by computer. Hellschreiber is very tolerant of noise and interference and requires only simple transmitters and receivers to work effectively.
|German Hellschreiber unit in operation|
With a microprocessor generating the digital on-off signals a simple crystal oscillator transmitter can be used to form a beacon station, one that transmits a call sign and perhaps some other information over and over. Changing the transmitted message is as simple as reprogramming the microprocessor or having it respond to a connected input, for Eg. A thermometer, light sensor, switch, etc.
|The ZL1HIT beacon using a PIC microprocessor and a simple crystal oscillator transmitter.|
For more information and the PIC microprocessor source code please visit the web page of Bryan Rentoul here : ZL1HIT Hellschreiber / PIC Beacon
George visits the Twit.tv studios and interviews Randy Hall, K7AGE. Tommy visits the Huntsville Hamfest. Jim builds an Audio Isolation Interface. Peter shows us the DATV QSO Party.