nikhil arora Posted June 9, 2006 Report Share Posted June 9, 2006 this was used in car alarm reciever 433Mhz, plz help me how this thing work Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 10, 2006 Report Share Posted June 10, 2006 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. Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 12, 2006 Author Report Share Posted June 12, 2006 and the first L and 5pf capacitor makes the tank ckt to select 433Mhz Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 12, 2006 Author Report Share Posted June 12, 2006 now after this stage in the ckt we have a stage using opamp this configuration of opamp is also confusing can u help me on this. Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 12, 2006 Report Share Posted June 12, 2006 The opamp circuit doesn't make sense as you drew it. If the opamp's inputs are reversed like I draw it, then it would be a Schmitt Trigger and would have a square-wave output. Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 13, 2006 Author Report Share Posted June 13, 2006 and what is use of capacitorsand when and how it will give outputs.i.e when it recieves 433mhz signals Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 13, 2006 Report Share Posted June 13, 2006 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. Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 22, 2006 Author Report Share Posted June 22, 2006 this RF reciever was in car alarm, how unreliable can be this reciever,i have got a 433Mhz module which is PLL and crystal controlledactually i want to ask how reliable this reciever can be... Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 22, 2006 Report Share Posted June 22, 2006 What 433MHz receiver?You posted the schematic of a very simple regenerative receiver that has only a single transistor. It doesn't use PLL and doesn't have a crystal. Better circuits are used in cheap remote controlled toys. Quote Link to comment Share on other sites More sharing options...
trigger Posted June 23, 2006 Report Share Posted June 23, 2006 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. Quote Link to comment Share on other sites More sharing options...
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