design 4 electronic eaves dropping device detector..plz help

[opampopamp]

can u plz help 2 design this circuit?its an electronic eaves dropping device detector working in the range of 1-1000mhz..parts list is given...plzz......help...its urgent....
R1 = 39 K; C1 = 10nF ceramic
R2 = 470Ω; C2 = 47µf/16V electrolytic
R3 = 22Ω; C3 = 10nF ceramic
R4 = 100Ω; C4 = 1nF ceramic
R5 = 560Ω; C5 = 10nF ceramic
R6 = 1 MΩ; C6 = 10nF ceramic
R7 = 220 Ω; C7 = 10nF ceramic
R8 = 100 KΩ; C8 = 10nF ceramic
R9 = 4.7 KΩ; C9 = .1µF ceramic
R10 = 1.5 KΩ; C10 = 10 µ/16V electrolytic
R11 = 10 KΩ; Chip :
R12 = 220 Ω; IC1 = LM324 1C
R13 = 10 K; Transistors :
R14 = 100 K; TR1 = BFR 90A
R15 = 470 Ω; TR2 = 2N2222
R16 = 47 K; TR3 = 2N2222
R17 = 47 K; Diode :
R18 = 1 K; D1 = NTE 112
R19 = 10 K; Potentiometer :
R20 = 100 K; P1 = 4.7K
R21 = 47 K; Other :
R22 = 10 K; ΑNT = telescopic antenna. Radio type.
R23 = 47 K; LS = Loudspeaker 8Ω

 

[betwixt]

Re: design 4 electronic eaves dropping device detector..plz

What exactly are you asking for, you have shown a design already.

It's a bit weird, I'm not sure about the audio stages but it should pick up AM signals (but not FM) over very short range.

Brian.

 

[opampopamp]

Re: design 4 electronic eaves dropping device detector..plz

actually..i hv a ckt wid me..also know the values of resistors and capacitors in it....i m doing it as a project..hence want 2 include the ckt design in the project report..since it is a high frequency ckt,donno hw 2 design it nd all.....so plz help me 2 design it..

Added after 1 minutes:

actually.....hw these resistors nd all got these values.....want that design.....

Added after 1 minutes:

searched abt it...gt dis much xplanation....bt i want a clear design of resisitors nd capacitors used here..
The detector detects an RF signal ranging from 1 to 1000 MHz. Figure 1 shows the schematic diagram of the detector. When the electronic bug operates, it emits an RF signal. This signal is received by the antenna (point 1 of figure) and is applied to the base of the transistor TR1 through a high-pass filter. The high-pass filter consists of the capacitors C4, C5 and the resistor R7.
When low frequency signals are applied to the input of the filter, the capacitors C4 and C5 operate as open switches and the filter rejects the low frequency signals. The cut-off frequency of the high-pass filter is defined to be 60 Hz rejecting any interference which come from the mains. The transistor TR1 is in common collector conjunction and it is used to amplify the signal. The gain that is provided is 10dB for a signal that varies in the frequency range 1 - 1000 MHz. The resistors R1, R2, R8 form the biasing network for the transistor TR1. The amplified signal is then applied, via the capacitor C6, to the anode of the diode D1. The diode is particularly manufactured to operate in high frequencies, since a common diode can not go from the conduction condition to the cut-off condition very fast preventing the appearance of reverse currents.
However the operation of the diode in the high frequencies range results in the appearance of conduction at the beginning of the negative half period. The potentiometer P1 adjusts the proportion of the signal at the terminals of the diode D1 and applies it to the inverting input (pin 2) of the operational amplifier A1. The operational amplifier A1 is configured as a very high gain amplifier. The value of the gain is defined by the capacitor C8 and the resistors R6 and R12. With no signal input from the antenna, the output of A1 at pin 1 is near ground potential. When the antenna detects a signal in the range 1 - 1000 MHz, it applies it to the base of the transistor TR1 producing a negative-going voltage at the cathode of diode D1.

That voltage is applied to the inverting input of A1 which amplifies and inverts the signal, producing a positive-going output at pin 1. The next stage after the opamp A1 is a voltage controlled oscillator (VCO). The oscillation frequency of VCO is controlled by the output voltage of the operational amplifier A1. The operational amplifiers A2, A4, along with the resistors R11, R13, R14, R16, R17, R18, R19, R20, R21, R23, the capacitor C9 and the transistor TR2 are arranged to form a voltage-controlled oscillator (VCO) that operates out of the audio-frequency range. As the output of A1 increases, the frequency of the VCO increases. The VCO output, at pin 8 of the operational amplifier A4, is fed to the input of A3, which is configured as a non-inverting unity gain (buffer) amplifier. The output of A3 is used to drive the transistor TR3, which, in turn, drives the output speaker.

 

[FvM]

Re: design 4 electronic eaves dropping device detector..plz

In other words, it's a wideband level detector with an acoustic indicator that changes it's frequency according to the input
level. The sensitivity can be adjusted.

The detector has no capability to demodulate a signal. It's operation is based on the assumption, that the searched transmitter
identifies itself by a RF level above the enviromental background. Seriously, I don't know if the assumption is justified.

 

[opampopamp]

Re: design 4 electronic eaves dropping device detector..plz

ya..its true dat d detector is nt demodulating d signal...its just changing the frequency of the output signal according 2 d variations in the input voltage level.....by making use of a VCO.....

Added after 1 minutes:

bt i want d design of those components used....in ckt....

 

[Audioguru]

Opampopamp,
Your English is horrible. Please use proper spelling and grammar.

At Electronics-Lab there were many complaints oubout this project that does not work.

Its input is not tuned so it amplifies and is overloaded by every radio and TV station in town. Also passing taxi-cab transmitters.
The very old quad opamp for its VCO amplifies its input offset voltage so they are saturated or cutoff.
The circuit is missing an offset voltage null adjustment. It also has other problems.

 

[nanisyako]

Re: design 4 electronic eaves dropping device detector..plz

What exactly are you asking for, you have shown a design already.

It's a bit weird, I'm not sure about the audio stages but it should pick up AM signals (but not FM) over very short range.

Brian.

what do u mean with that? if I test is with fm transmitter with 100 Mhz it will not picked it up.

 

[Audioguru]

Re: design 4 electronic eaves dropping device detector..plz

if I test is with fm transmitter with 100 Mhz it will not picked it up.

If the circuit is built with the proper parts and on the proper pcb (not on a breadboard) and if the circuit is not overloaded by every radio station, TV station and taxi-cab radio in town then it should give an audio tone indication that an FM transmitter is nearby.
It might not pickup a weak little FM transmitter since it is designed to pickup 1W from a cell phone. A weak little FM transmitter has an output power of only about 0.02W.

The audio is a voltage-controlled-oscillator. Its frequency should be zero if there is no radio signal pickup but the circuit does not have an input offset voltage nulling pot so it will probably produce a tone with no signal, or it will have a negative input offset which will make it not sensitive.
When it picks up a signal (just the carrier since AM or FM makes no difference) then the VCO will make a tone. The pitch of the tone increases with increased signal strength when the transmitter is closer.

The circuit and kit perform so poorly that the project has been deleted from Electronics-Lab.