This is just a variable oscillator based on a bf245 or k 161 fet. By changing the coil it can generate frequency between 0.5 and 300 MHZ. this circuit is useful to test radio circuit such as filter, receiver, transmitter and so on.
It can be used for coil tuning also thanks to the 100microA meter .It must be placed in a metal case. You can also use a double sided vetronite board, one for ground. To build it , is requested particular experience in radio-frequency assembling . First of all remember to put as short as possible all connections or you’ll have problems over 50 MHZ. .Coils are build as shown later using a 5 pins DIN plug . The central pin is used for central tap of coil . The variable condenser is that used in normal fm-am radio which as?? 20+20 and? 300+300 pF capacitance.
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