This is a typical 3 ½ digit TTL counter. We found it in the September 1973 issue of Radio Electronics magazine. The circuit is to be powered by 5 V. It can be expanded to more digits.
This line protector circuit was found in a 2002 documentation, but it is totally current and...
This antenna for the frequencies 146 or 440 MHz was found in a magazine 73 for Amateur Radio of...
With this circuit it is possible to increase the output voltage of a 7812 regulator. The circuit...