After many years of employing this ugly and clumsy bench power supply, I decided it was time to build something better, smaller and nice looking. It began as a variable power supply based on an LM338 5A voltage regulator and external power adapter. LM338's Data Sheet has several very helpful application notes and circuits. I chose one that illustrated variable output and included protection diodes. Diodes are included to protect the regulator from damage in case the input is accidentally shorted to ground. This is a distinct possibility if using jumpers to attach it to the power supply. Also the output of station supply may be shorted if some other device fails. Without the diodes, if this happens, the capacitors will dump their charge back through the regulator. Since the current spike may be many amps, the regulator may fail. The diodes steer the current around the regulator and into ground, thereby protecting it from damage. With adequate input the LM338 makes a fabulous variable power supply. This small supply is user friendly and fits nicely on my cluttered bench.
Build Accurate LC Meter and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging and reset function to make sure the readings are as accurate as possible ... [more]