throughout the years the humble 555 timer has been utilized in so numerous unforeseen places, however there’s a job from [Frank Latos] which we believe may be a first. On a piece of stripboard sit a pair of 555s, as well as instead of the typical passives there are a set of LC circuits. This is no timer, instead it’s a CW (Morse) transmitter for the 80 metre amateur radio band.
One 555 is configured as a comments oscillator with a toroidal transformer with a tuned circuit to set the frequency of oscillation. The other takes an inverted input from the oscillator to create free push-pull outputs from both 555s, which are fed to one more transformer that in turn feeds a low-pass filter as well as therefore the antenna.
Free-running squarewave oscillators of this type are not unusual for the lower HF bands, however we believe this is the very first 555 style we’ve seen. As shown it doesn’t create much in the method of RF power, however remembering half-decent motor chauffeurs utilizing a 556 double timer we believe that choice of one of the much more powerful 555 variations may provide some much more punch. We commend his imagination though, as well as hope he can get that all-important entry in the log to show it works.
If you’re curious about low-power radio operation, it’s something we’ve explored before.
