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This Selector Antennas using PIN Diodes Circuit Diagram selector antennas uses PIN diodes, was designed using common components and is very useful when used various external antennas, this antenna selector uses PIN diodes that eliminate disadvantages of mechanical switches especially at high frequency.  Capacitors C1 to C4 and C9 are used to prevent the input and output circuit DC. Shock L1 to L5 prevent leakage of HF signal.Shock L1 to L5 can be wound on a ferrite core, using enameled copper wire of 0.3 mm in diameter, two rounds will suffice for entries for VHF and UHF 5 (1 mH is required for VHF and UHF about 5 uH). The circuit was designed for antenna input impedance of 50 or 75 ohms. Selector Antennas using PIN Diodes Circuit Diagram

Function LEDs emit light when an electric current passes through them. Connecting and soldering LEDs must be connected the correct way round, the diagram may be labelled   a   or   +   for anode and   k   or   -   for cathode (yes, it really is k, not c, for cathode!). The cathode is the short lead and there may be a slight flat on the body of round LEDs. If you can see inside the LED the cathode is the larger electrode (but this is not an official identification method). LEDs can be damaged by heat when soldering, but the risk is small unless you are very slow. No special precautions are needed for soldering most LEDs.  Testing an LED Never connect an LED directly to a battery or power supply!   It will be destroyed almost instantly because too much current will pass through and burn it out. LEDs must have a resistor in series to limit the current to a safe value, for quick testing purposes a 1k  resistor is suitable for most LEDs ...