QRP RF Actuated Changeover

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This kits design was originally provided By Rev. George Dobbs (SK) for the RSGB magazine DIY Radio. Kanga Products were asked to provide a kit of parts for the project. The circuit is fairly straight forward, with the transmitted RF sensed by transformer L1, which is fed to a pair of diodes then to TR1which acts as a high speed switch. 

The minimum power levels that this unit will work at on Top Band (1.8 – 2Mhz) is approx 500mW, it will switch less on the higher HF bands with a minimum of 100mW on 10m (28Mhz) The maximum power handling is 5 watts. With a 47µF capacitor at C1 the hang time is about one second, C1 maybe reduced for those that require full break-in.