The secret is in the oscillator stage, it should oscillate and be tuned. Check the voltages on potentiometers.
Use correct capacitor and coil values for each selected band.
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Did you connect the varicap correctly? Check its voltage when tuned by the pot.
I can't see that ever working reliably.
I presume it is supposed to work as a zero IF receiver with detection using the B-E junction of the top BF199. It would rely on the oscillations starting before it could bias the transistor to start the oscillations - not a stable condition! The capacitor values also look suspicious as well, I would imagine the tuning range would be very limited as the varicap is swamped by larger fixed values. Basically, it's an incorectly biased oscillator with a poorly designed wideband antenna amplifier connected to it.
Brian.
Sometimes you have to ask before build...
Thanks Brian
A regenerative receiver is used in a child's cheap toy car. Make a real radio instead.
The schematic uses BF199 NPN transistors but wrongly shows them as PNP. I wonder what else is wrong with the circuit?
Image rejection? I do not think so. The image in a regen is the opposite sideband, like a common DCR. The selectivity of the Q-multiplier is not so good to reject the opposite sideband.Regenerative receivers have a lot going for them. No images, good overload performance, good selectivity and they work with AM, DSB and SSB. They can also receive FM subject to the normal lmitations of slope detection but consider that in a regenerative receiver you can adjust the slope! Their only real disadvantage is the difficulty of tracking the regeneration and maybe pre-amplifier tuned circuits.
I wonder if a good regen design exists somewhere. Kitchin's design https://www.google.gr/url?sa=t&rct=...MCFap8NU2lsBCxpC7x1LWRQ&bvm=bv.95039771,d.d24 seems good but is it really? Also the multi-tapped coil is scary. My thought is for a tap-free coil, this would be great!The particular design shown has lots of limitations and like most designs on the internet, is based on trial and error using bits fom a junk box instead of using good theory and selected parts.
That is what I have also thought, a microcontroller that controlls both frequency and the feedback loop. But the micro has to be a "learning device" since these curves difference is not always the same and they are not linear.I have in mind a new approach, call it "Betwixtodyne" which works in theory but to my knowledge has never been built. It allows continuous tuning with tracking of the regeneration point. It makes the regeneration control a bandwidth control instead with the option to go 'negative bandwidth' to resolve DSB and SSB. I will get around to trying it one day but for now it just bounces around in my head. I suppose that's because there's lots of empty space there. :grin:
Brian.
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