detector prototype

[audioguru2]

Badai,
You may have a problem by using this project:

Our Projects Section has an Electronic Eavesdropping Detector project that may be suitable if you use much bigger capacitors for C4 and C6 (marked D1 by mistake) so that it picks-up lower frequencies.
But if you have any near-by radio or TV stations then the above circuits will pick them up instead, since they are not tuned.

An LM324 will replace the MC3403, and a 1N34A diode will work in this project.

 

[badai]

since my project cover in wide scope, then my supervisor want me to design the detector for detecting cellular phone only. nowadays, we find that some places like in hospital, aeroplane even in exam hall(to cheat) and etc. we does not allow to use the phone to avoid any problem. so, my detector suppose to detect when somebody using their phone in that area. as we know when the phone getting close with the radio, we can detect the noise. is it hard to design my hardware using the tune radio circuit or any possible circuit?

audioguru, in this website http://www.electronics-lab.com/projects/rf/005/index.html , can you explain what the number in circle for, and the pin 4 and 11 how to connect it?

 

[audioguru2]

Badai,
The Eavesdropping Detector project might be sensitive enough to pick-up a nearby transmitting cell phone without tuning, if it isn't overloaded by nearby radio or TV stations.
If you could add some kind of tuning circuit to it, you won't know which cell frequency is used. Some cell phones use "spread spectrum technology" where the frequency continues to change.

The circled numbers on the schematic refer to connections that are external to the PCB, such as antenna, speaker and battery.
Pins 4 and 11 are the power supply pins for the IC, and are already connected on the PCB.

 

[badai]

i've few questions here:

1-some cell phones today using dual band and tri band type. is it make any effects on the circuit?
2-in my country(malaysia) we using some types of network: celcom(900MHz), adam(1800MHz),digi(1800MHz),maxis(900MHz) and tm touch(1800MHz), so can you explain how these operating frequencies is working with this circuit?
3-this circuit is operating on the range of 1-1000MHz frequency. then, let say i'm using digi network, could the circuit detect the cell phone?

 

[badai]

i learn that EMI will occur when these three elements exist, source of emission, coupling path and receptor. so, i'm using cell phone as a source of emission and tune radio as a receptor. anyone can explain about the coupling path under this condition?

 

[audioguru2]

Hi Badai,
Have you built your detector yet?

A good coupling path is short, directionable and without obstacles. Antennas should have the same polarization (turn your AM radio around and hear the difference).
A poor coupling path is from here to the planet Pluto, with the Sun in between! (or with a shield around the source of EMI)

 

[badai]

actually i hold to build the circuit for a while. so, right now i'm doing few experiment and it still related with the circuit. audioguru, i know you are expert in theory, so can you explain this situation clearly?: a hand phone operating at 1800MHz frequencies, a local service provider using the same frequency so the hand phone can receive and transmit the signal to another person. when i put my detector close the hand phone, is it mean that my circuit is detecting noise at the 1800MHz frequencies?

 

[audioguru2]

Hi Badai,
Your untuned detector will probably pickup local TV and radio stations and any other nearby transmitters such as taxicabs.
It may not be sensitive to a hand-phone that is transmitting at an extremely high frequency of 1.8GHz, unless proper UHF and microwave wiring techniques (wave-guides) are used.
The only way to confirm that the tone from the detector's VCO is caused by it detecting the hand-phone's transmitter is by turning the hand-phone on, off, on and off and hear if the tone follows it.

 

[badai]

the component with series BUZ 90A and BUF 90A, is it both same components???..............

 

[badai]

the telescopic antenna........is it the antenna used by tuned radio??

 

[audioguru2]

Hi Badai,
Are you looking for parts to make the Eavesdropping Detector project?

A telescopic antenna is the kind that you pull to make longer or push-in to make shorter, like used on toys and old wireless phones. A stiff piece of wire will replace it.

Can't you find a BFR 90A transistor (you should spell it correctly)? Don't just pick any transistor with the same number like a BUZ 90A power Mosfet, I recommend looking at the BFR 90A datasheet on Google and finding a transistor with similar high frequency spec's. I bought a similar transistor at a local electronic parts store and it was made for TV RF amplifier boxes.
Highlights of the datasheet for the BFR 90A are here:

View attachment 36648

 

[badai]

I'm using eagle editor layout.......for BFR 90A what kind the symbol should i use from library because this transistor not same like common NPN transistor but the symbol from circuit given same like NPN transistor

 

[audioguru2]

Hi Badai,
On a schematic a BFR 90A looks like any common NPN transistor. On a pcb layout, use its package number and pinout as on its datasheet.

 

[badai]

for R13 at the +ve point it should be connected with pin 4 for IC1. is it right?

 

[badai]

another one is all the grounded components should be connected together to pin 11 isn't it?

 

[audioguru2]

Hi Badai,
You are correct, the posivive end of R13 and the positive terminal of the 9V battery connect to pin 4 of the IC.

Again you are correct, the grounded components should be connected together to pin 11 and to the negative terminal of the battery.

You might put an on-off switch between the positive terminal of the 9V battery and the circuit.

 

[badai]

after i finish design schematic using EAGLE, i click to BOARD button, then i follow the instruction but when i clcik AUTO button, EAGLE cannot perform this command but on my schematic no error and warning was found. What is the problem?

i didn't found this diode symbol BA481(OR NTE112) in library, so how should i do?

 

[badai]

i'm not so sure the symbol for potentiometer(P1), i'm choosing PC16S but it has pin E, S and A. which one should connect with R12?

 

[audioguru2]

Hi Badai,
What are you doing with Eagle?
Haven't you seen the project?

View attachment 36664

 

[MP1]

Badai,
I congratulate you on your motivation to learn Eagle. Once you have used it for a while, you will wonder how you went without it.
For the diode, you can use the 1N4007 package to get a footprint that will work for you.
You can use any 3 pin connector for a potentiometer if it will be mounted off the board. Otherwise, use a package that you know you can purchase. You have this latitude because you are the board designer.
When you go to the board layout, you must place the parts on the board where you want them to reside. Then, if it is a single sided board, set TOP to N/A and set the bottom layer to * in the auto router setup window. Set the routing grid to 50 mil and click the ok button. The program should start the routing.
Please let me know if you have any other questions regarding Eagle.

MP