Conversation
Notices
-
@tomas it's just my expectation without "knowing" the device: It's just a headphone pre-amplifier stage. Not even the headphone is connected directly to the tube stage (you would have needed a transformer to do this) but there's a transistor stage after the tube. So everything will be small in that tube. Things get different with larger tubes, e.g. the output stage of a tube radio with 5 watts output to the loudspeakers (via transformer). Larger tube→larger filament.
-
@tomas some time I build a #shortwave #regenerative tuner (in German called Audion)Â with 1 tube like this: http://www.elexs.de/radio3.htm
You get NF out of it, and with a 2 transistor NF ampliflier I connected it to audio-in of my PC. The tuner was good enough to receive Radio Tehran/Iran in good quality in Germany. Isn't that amazing for that few parts? I used a 5 metre wire as indoor antenna.
You could also listen to #SSB transmissions (with no additional parts!) and in theory I should have been able to listen to #DRM (Digital Radio Mondiale) via SDF but my pentium 3 was too slow to decode it, but the signal was there.
-
@tomas #regenerative receivers have an additional feedback loop. For AM you are supposed to adjust the feedback as high as possible just before the circuit starts oscillating itself (whistle sound). For SSB you adjust the feedback a bit higher for a bit of oscillation. If you adjust it to too much oscillation the receiver even becomes a transmitter :-)
https://en.wikipedia.org/wiki/Regenerative_circuit#Superregenerative_receiver
Tubes aren't about low distortion :-) Tube have their typical "wanted" distortion :-) It gets warm, it sounds warm, there's some orange light glowing... fun to use and to watch :-)
mcscx2old
All bartle content and data are available under the