As noted in a brief addition at the proof stage to the March TT, Dick Rollema, PA0SE, has made several corrections and changes to the circuit diagram of his 136kHz transmitter (January TT, Fig 2). He writes: "At first the transmitter operated without any problem. But after returning from holiday one HEXFET after another failed. Fortunately they are quite cheap. After the demise of seven semiconductors I found the cause: parasitic oscillations on VHF or UHF. The remedy was clear from the valve era: stopper resistors (120Ω) in series with the gates.
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