Regenerative Radio Receiver Circuit

On a sunny day (Tue, 28 Aug 2012 00:40:27 -0700 (PDT)) it happened iiiijjjj wrote in :

The problem with thsoe thingies is that they radiate a lot at the Rx frequency, causing reception problems for others.

Practical Wireless magazine published a design/kit for a regen with a grounded gate JFET front end that pretty much isolated the antenna from the possibly lively bit.

It was called the Knapp receiver IIRC.

Regens don't oscillate. Superregens do.

I like the LEDs as bias voltage sources, especially if you use different colors. Makes the board look cool.

frequency,

You nearly made it:

Regens *should* not oscillate (but they occasionally do).

Amateur radio regenerative receivers used for CW reception are adjusted to oscillate -- the audio tone is generated by the mixing of the self- oscillating frequency and the desired signal.

But that's a corner case -- a regen that you might find in some piece of consumer gear shouldn't self-oscillate (but might, depending on how well and how long ago it was adjusted).

tp://evospice.site88.net/regen/regen.html

I thought regens went out after Major Armstrong's invention became popular.

The tiny outlay is popular with many experimenters & SWLs.

AFAIK they're still used in el-cheapo consumer equipment like toy cars, key fob remotes, garage door openers & such.

Slowly being overtaken by super-small "regular" radios, but still out there.

alike:

As detectors, that's right. However, positive feedback (regenerative) circuits used to be used quite widely to sharpen up the response of HF receiver front ends, where they were called "Q multipliers".

Cheers

Phil Hobbs

On a sunny day (Tue, 28 Aug 2012 21:37:48 +0100) it happened "Ian Field" wrote in :

Xcuse me with that many components you can make a good superreg!

Xcuse me with that many components you can make a good superreg!

SORRY I MENT TO SAY SUPERHET :-)

Are you squaking like the receiver?

On a sunny day (Wed, 29 Aug 2012 18:56:42 -0700) it happened Robert Baer wrote in :

frequency,

No but you are

I guess an interesting point is that the (AC linked) differential pair has = a tanh input amplitude versus gain curve. The requirement that the transis= tors be matched in the usual (DC linked) long tail pair is a DC biasing onl= y requirement. The two transistors in the AC linked version can be very dif= ferent and still give symmetrical behavior. Anyway the slightly compressiv= e tanh response allows for a smooth transition into oscillation with increa= sing positive feedback. A lot of circuits on the internet use FET's for reg= eneration. There you have to hope that you can bias the FET into a region = of its operating curve where the gain it provides is compressive (decreases= slightly with increasing input amplitude). Even the well know designs by C= harles Kitchin in QEX do not address that problem and are kind of hit and m= iss.

Hmm, that can't be right. Surely you meant output vs. input (i.e., transfer function), not input vs. gain? Also, atanh?

Tim