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One tube radio

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I was just reading a russian forum and I found this project. Its a radio receptor, with the tube 6ba6, I supose that its for AM or SW bands. I have some 6ba6 laying around here, so I decided to give a try to this radio. Anyone can explain to me how this works?

Note: I dont know how this coil have to be.. A conventional ferrite coil from a AM radio may work? And any chance to try a FM coil (if i change the variable to 5~60pf) ?
 

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Yes, that's an AM broadcast band setup. Change the tuning "tank" and it will work on the longer SW bands. The circuit is a grid leak detector, with regenerative (positive) feedback. The feedback control is adjusted to bring things just shy of oscillating. You will hear a "plop", when oscillation starts. Should that occur, you have to back all the way off and start over.

For a 1 tube FM setup, a super regenerative detector is in order. Look here.
 
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Regenerative radio receivers can be a lot of fun, one thing to bear in mind is that they can (and often do) radiate RF on the antenna if allowed to actually oscillate which can be a problem when used for CW or SSB reception (badly in this case), since SW and BC bands generally use AM this should not be a problem.
 
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