50 (FET) Field Effect Transistor Projects - Battery Portable

Should the field strength meter be wanted for VHF only, a VHFchoke can be used, but for general usage over lower frequencies,a short wave choke is necessary. An inductance of about2.5mH is satisfactory for 1.8MHz and higher frequencies.The device can be constructed in a small insulated or metalbox, with the aerial projecting vertically. In use, it allows tuning upa transmitter final amplifier and aerial circuits, or the adjustmentof bias, drive and other factors, to secure maximum radiated output.The effect of adjustments will be shown by the rise or fall ofthe reading of the, field strength meter.Gate DipperFigure 23 shows an extremely simple resonant dip oscillator. Itcan be used over a wide range of frequencies by the use of plugincoils. With such instruments, the coil generally projects at oneend of the case, so that it can be brought near to the inductors ofother tuned circuits.