This preamplifier for the 6 or 2-meter range was obtained from an American documentation from the 1980s. FETs can be modern equivalents and no information about the coils is given.
With the coded activation of the relays, it is possible to control which of the 16 outputs...
The integrated circuit used in this application is not very common. Transistors and resistors...
This simple circuit makes use of neon lamps to indicate the voltage of a power grid. The lamps are...