Simple tube transmitter for 80m and 40m (AM / CW)
Without the effort being greatly increased, a much more stable transmitter could be set up with a combination tube, such as the in Germany called QRPeter, which was then popular as a beginner's device. That was a single-stage transmitter for the 80m band, mostly assembled with an EL41 or a EL84. At higher frequencies could hardly be achieved with such transmitters a useful frequency stability. Different at this simple two-stage transmitter: The executed in Hartley arrangement RF oscillator always worked here in the 80m range. If one made the PA coil interchangeable, can doubling the frequency and so the transmitter can be used also for the 40m band. In the 80m band could be with about 5 watts, however, certainly produced slightly more power, as in the 40m band.
Because the oscillator's anode voltage was switched by the key, an isolated design had to be used. Another possibility was to use a relay to switch.