A regenerative receiver uses positive feedback to increase amplifcation significantly. The principle was invented around 1912 by Edwin Armstrong, so the early days of radio. The principle enables you to design one or two tube (or transistor) radio's with loudspeaker output.
The radio has one disadvantage; you have an extra potentiometer to adjust the level of amplification (regeneration in fact). So this type of radio is interesting when you like to fiddle around with buttons and knobs.
I ran into a design of Jack Donio. It is an 0V1. Since I had a bunch of retrieved components from a Blaupunkt tube radio I started building the design.
As you might know I am fascinated by radiostuff from the pre-transistor area; I built this radio with a positive result. I made some small adjustments; the complete PSU was available from the old Blaupunkt radio so I used that. Also I used the tube ECC85 instead of ECC81. I did not make the coil according the instructions but I had one, very similar, in the junk box.
The radio turns out to be quite sensitive. The EL84 provides sufficient audio output. The frequency range is 9..15 MHz. Last days, especially in the evening, there are a lot of broadcast stations to listen to. I heard China, Bulgaria, Iran AM stations. The best way to receive AM signals is to find the spot where the receiver is on the edge of oscillating. Of course you need a long wire antenna (at least 10 meters).
The variable capacitor on the left is for coarse tuning. The one on the right for fine tuning. The last one is required to tune into HAM radio signals in the 10 MHz and 14 MHz band. To my surprise I heard quite a lot of CW signals. The SSB signals in the 14 MHz are quite hard to adjust to. But not impossible. You need care to play with the fine tune capacitor and the regeneration potentiometer.
I also added an EM80, the green magic eye. Just for fun.
I am now in the phase of final adjustments and putting some placards near the controls. It was a fun excercise in building vintage radio in this era of microchips, semi-conductors and plug-and-play transceivers from Aliexpress.
