Jump to content
Electronics-Lab.com Community

Plz help me in understanding this RF reciever


Recommended Posts


It is a regenerative receiver that is connected so it nearly oscillates due to positive feedback through the 3.3pF capacitor.
The transistor is a common-base oscillator, but with not quite enough positive feeddback to oscillate. Its gain at the tuned frequency is extremely high.
It might also be a super-regenerative receiver where a signal causes its output level to build up until it oscillates and it cuts itself off at a fast rate called its "squegging" frequency which keeps its gain at its most sensitive.
Google has many examples of regenerative and super-regenerative receivers.

Link to comment
Share on other sites

The capacitors in the opamp circuit are filters. The larger capacitor following the 100k resistor smooths the output of the receiving transistor to DC. The 1nF capacitor has a small value and smooths the 433MHz but allows the signal's modulation to pass to the opamp.

Look up Super-regenerative Receiver in Google. It is a very simple AM receiver that gets cutoff when it receives a carrier. When it is cutoff, its output voltage goes high which causes the output of the opamp in my drawing to also go high.

Link to comment
Share on other sites

  • 2 weeks later...

If it has a crystal, it is a superheterodyne receiver with local oscillator, typically 10.7MHz.

It is much stable than the super-regenerative receiver.

But I can tell if the layout and circuit is fine-tuned for the regenerative circuit, it won't do any significant differences in performance with heterodyne one.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
  • Create New...