Posts Tagged ‘RF-Radio Frequency’

Car Burglar Alarm system with radio wave signal

When steal open automobile door relay K1 and K2 work make have voltage 12V give radio transmitter and origin sound part for mix radio waves steal will deaf anything sound. Because radio high frequency. But car owner will hear the sound , by take handbag very small radio, tune the frequency directly with the frequency of a transmitter. Which there is just not mW as a result the enough. A transmitter will still work for 15S (fix the time has with R3 and C1) although the door will open then follow thereafter radio transmitter will stop to work. Because of Transistor stop bias relay contract K2 be scratched. The transistor that use must durable current change relay get. If use battery separate separately and use an antenna model to draw start up the motor this use within a car , steal will can not cut the work has of from the outside.

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A BIPOLAR REGENERATIVE RECEIVER

Contrary to what some radio experimenters think, a bipolar regenerative design can be made to work efficiently. The major concern is the low input impedance of the detector-amplifier bipolar stage. Nevertheless, it can be easily compensated with positive feedback or regeneration. A sufficient amount of regeneration can make tuning astonishingly sharp. Another concern is the quality of the detected audio. This, to my knowledge, is subjective. The quality of sound coming out from an earphone can be rated good or fair by two different people. I would suggest that you decide by yourself. So, come on and try the following schematic for the 530 kHz to 1650 kHz AM Broadcasting Band.

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Read More Source:Circuit : Ramon Vargas – Lima, Peru.

http://www.mitedu.freeserve.co.uk/Circuits/rf/regen.htm

Thank you.

A Simple-To-Build Superhet Receiver

This idea presents a simple circuit for a superhet radio receiver that can be built up in sections, with each section tested before assembly. The receiver circuitry as presented here can be built for less than $50.

Don’t be misled—even though the set has some pretty obvious limitations as presented, it’s still capable of worldwide reception when connected to a few meters of wire as an antenna. When constructing a superhet receiver needing just one coil/tuning-capacitor combination, there’s the obvious advantage that only one simple coil needs to be made. It also makes the receiver very easy to experiment with by changing the coil dimensions, etc.

Read More Source:

http://electronicdesign.com/Articles/Index.cfm?ArticleID=4378

Thank you.