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.
This circuit was found in a Texas Instruments optoelectronics documentation. The gain depends on...
This oscillator circuit is from a Radio Electronics magazine from September 1960. The frequency depends...
Using a reed relay, this protection circuit depends only on the adjustment of the closing point by a wire...