This article describes another variant of the Simple Morse beacon keyer project. This one is cut down to the basics, but does include crystal timing for some serious QRSS experiments.
Fig 1 shows a basic implementation of the keyer using an ATTiny25. This keyer uses a crystal clock oscillator for more accurate timing, allowing "image stacking" as discussed at QRP QRSS Beacon Transmitter - on air. Experience is that if the keyer is kept to a fairly constant temperature, it keeps time to within 100ms per day, or about 3s per month.
This variant has a set of DIP switches for selecting one of four speeds (12WPM, QRSS1, QRSS6, QRSS15). Most HF grabbers have FFT bandwidth and capture cycle optimised for QRRS6 so it is more or less the standard, though some of people use different things, often at the expense of bandwidth and performance.
The two pin male header is for programming using ATB (AVR Tiny Bootloader), Simple Morse beacon keyer - using ATB. ATB allows message replacement (or firmware upgrade) using a simple USB-RS232/TTL adapter, eg the OPC478U adapter and the ATBU utility program.
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