To anyone who wants to deal with the construction of receivers, I still recommend today to make initial attempts with a regenerative receiver. This is very instructive and one develops a feel for the behavior of oscillating circuits and the mechanical requirements of the tuning devices. My first attempts at simple regenerative receivers made with transistors did not lead to the hoped-for success. To make matters worse, that the transmission tower of the Hamburg medium wave transmitter was not far away from us. The transmitter, which until recently was operating at 972 kHz, could be heard virtually over the entire waveband with each circuit. It was therefore hardly possible to receive other channels. At first, even a blocking circuit inserted into the antenna line barely changed anything.
I then built my first really well-functioning regenerative receiver with tubes. Here, the much smaller damping of the resonant circuit by the high-impedance tube input made advantageous noticeable. With a tuned to the medium-wave local transmitter blocking circuit in the antenna cable, I was now able to achieve usable reception results, without the powerful medium-wave transmitter knock through everywhere. One triode system of the ECC81 worked as an audion detector, the other as an audio amplifier. The regeneration adjustment was made via a rotary variable capacitor. At 80m and 40m, the device worked quite good. But it was disadvantageous especially when receiving SSB and CW stations, however, that changed the reception frequency not insignificant with the setting of the regeneration feedback. Above about 10 MHz, the device was therefore actually only usable for the AM reception. After all, depending on the propagation conditions strong broadcasting stations in the entire spectrum of the shortwave were so loud receivable that the gain of the single-stage audio part was sufficient for speaker reception. For the amateur radio reception, however, a headphone had to be used.
With such a tube circuit, the words of Heinz Richter, which he wrote in his "Neues Bastelbuch für Radio und Elektronik" (New Tinker Book For Radio And Electronics) in context to the Trabant KM presented there, came true for me for the first time with a completely self-built device: „Those who are concerned with the reception of shortwaves, will probably like to give up the night's sleep and into the early morning hours enthusiastically turn the tuning knob of his shortwave receiver. The reception of shortwave is extremely exciting, numerous stations from all parts of the earth can be heard. It can happen that the announcer of any station with the good night greeting say goodbye to the listeners, while at the same time from another distant station a morning greeting arrives.“