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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?

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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.

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  • 6 months later...

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:

post-1706-1427914214154_thumb.gif

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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.

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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?

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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

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thanks so much for helping me......... ;).......now i understand to use this software....and hopefully can improve better after this.....actually i can't get this component (BFR90A) in my local shop, i bought wrong component actually before this....another series (BFG90, BFQ28, BFR24, BFR49) also didn't find. what should i do now????

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Hi Badai,
Transistors having that unique package and pinout are made for very high frequencies. I found one in a cheap cable-TV amplifier box.
Show the picture of the transistor at your local shop and they might have an equivalent one.
Otherwise, an ordinary general-purpose transistor like a BC547, 2N2222 or 2N3904 will work in this circuit up to about 200MHz. A BC594 will go higher. Their pinouts are all different.

What do you hope to detect with this project?
Using general-purpose transistors, it will probably detect a little FM transmitter up close, if it isn't overloaded by local radio and TV stations.

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To complete the board layout, you can use a 2N3904. Then you can use any transistor with the same package type and pin out. You should get the data sheets and compare the transistors listed by audioguru and choose the closest one that is available to you.

Good to hear you have Eagle figured out!

MP

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where is R17? i didn't find it in circuit diagram but this component had been placed in layout board , is it missing?

this is my schematic circuit. can you check for me either right or not? i'm using pad 1(wirepad) to connect my antenna, is it right?

why my +ve and -ve(supply symbol) point not occur in my layout?

post-2302-14279142146314_thumb.gif

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It looks like the author missed R17 on his schematic, from pin 12 to ground like R15 on the other side.

In my country, cell phones operate at GHz frequencies. A 300MHz 2N3904 won't work unless an operating cell phone is very close to it.

I don't know why you re-drew the schematic without using opamp symbols.

EDIT (Mar 7/05): I said R23 when I meant R15.

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1- i just scatch back, is it like this you mean?

2- So if the phone operates up untill 1900MHz, which one is appropriate transistor(except BFR90A) from list you given?

3 - In my previous circuit ff i'm using pad 1(wirepad) to connect my antenna, is it will work for my antenna?

post-2302-14279142146631_thumb.gif

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Hi Badai,
None of the "general purpose" common audio amplifier transistors that I have listed will work above about 200MHz to 300MHz.
To receive 1.9GHz, you need a microwave transistor better than the BRF90A, which can receive up to only about 1GHz.

The BRF90A has no gain at 6GHz, a little gain at 3GHz, a gain of about 2 at 1.5GHz and a gain of about 3 at 1GHz.

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Badai,
In Eagle, you must choose the correct IC package for the ICs used. You should be able to find most common op-amp packages in the "Linear" library. The IC-Package library is there in case you cannot find something that works.
Pay close attention to vcc,vee,vdd, etc on the library package as this will be the name of your bus. Then when you want to connect the grounds of all components to this bus, it will be correct. There will be no connection shown on the schematic for the power lines of the IC package. They are automatically connected on the board layout.

Hmmm....maybe we should split this post and put some of it in the CAD forum. If you have more questions regarding Eagle, why not post them in the CAD area so others who perform a search will be able to find previous posts on the subject.

MP

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