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900Mhz/1800Mhz Cellphone detector

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frenchneco

New Member
My team needs to build a cellphone detector. The 900MHz & 1800Mhz band is being used in our country. Effective radius of detection could be 1 meter - 2 meters. Detection could be in any form (sound, LED, etc)

Does anybody have a working circuit already?
Do we need detect at both frequencies?

Thanks
 

Papabravo

Well-Known Member
Building circuits to operate in this frequncy rage is both difficult and expensive. It is not for the faint of heart or the weak of wallet. PC boards need to be carefully designed and fabricated with tools that are quite beyond the reach of weekend hobbyists. The test equipment is a whole other story when it comes to expense. You need to find something to buy, unless you light your cigars with $1000 bills. The ones with the picture of Woodrow Wilson that are no longer in circulation.

BTW, commercial radios generally block those frequencies so I think you might be outa luck unless you are a government agency.
 
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frenchneco

New Member
we saw this ckt in the net. do you think this would work?

Cell phone detector

we assembled it and can't seem to make it work. the 555 is oscillating, the LED is on, and the buzzer is making a very annoying sound. the problem is that the mosfet is not latching.
 

blueroomelectronics

Well-Known Member
Did you read the comments on that project? Pretty much all looked like this.
can u send me detial workig of this circut i am student of QAU. i will be very thankful to u.
Reply
Ahh it's an EFY project, they are generally untested crap.
sir im havin problems wid de circuit..de alarm goes off as soon as de circuit is given power..also i wud like to have de design details of de circuit..please help!!!!
 
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frenchneco

New Member
what's an EFY? awwwwww... anyway it's still bad news for us. we really need help. we're desperate. we only have less than a month to make a project. we badly need WORKING and TESTED projects.
 

blueroomelectronics

Well-Known Member
Why not choose a project you have knowledge about? What's the point of submitting someone else's work?

EFY = Electronics for You.
 

frenchneco

New Member
the problem is we only know little. honestly, we're in a very tight situation right now. we really need all the help now. :(
 

frenchneco

New Member
just very bad quality of education man. some schools are just like that. i know we should have done our part. but it's too late now. i hope u understand. sometimes, sh*t just happens.
 

crutschow

Well-Known Member
Most Helpful Member
we saw this ckt in the net. do you think this would work?

Cell phone detector

we assembled it and can't seem to make it work. the 555 is oscillating, the LED is on, and the buzzer is making a very annoying sound. the problem is that the mosfet is not latching.
Did you lay it out as stated with all component leads as short as possible? At those high frequencies, a careless layout with long leads will not work.

It does not show on the schematic but there should be a 0.01µf decoupling ceramic cap directly across pins 4 and 7 on IC1 (as short leads as possible).
 

Papabravo

Well-Known Member
Did you lay it out as stated with all component leads as short as possible? At those high frequencies, a careless layout with long leads will not work....
I did warn you about this. Remember?
I think you may be SOL. I guess that happens too -- so sorry.

PS I don't think it has the slightest chance of working.
 
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frenchneco

New Member
Did you lay it out as stated with all component leads as short as possible? At those high frequencies, a careless layout with long leads will not work.

It does not show on the schematic but there should be a 0.01µf decoupling ceramic cap directly across pins 4 and 7 on IC1 (as short leads as possible).
yeah. and we made its pcb as small as possible. tnx for the help mate!
 

audioguru

Well-Known Member
Most Helpful Member
The simple circuits might pickup every TV station and every taxi-cab radio in town.
The GSM sniffer is just a simple crystal radio with an audio amplifier.
 

Papabravo

Well-Known Member
since i'm SOL, could you help me? :)
I'd like to, but I can't imagine what you actually need. It seems, and correct me if I'm wrong, that you want to snag some kind of circuit off the internet that you can build and pass it off as some kind of project for some kind of credit in some kind of course. I personally don't think that this activity will be very beneficial since becoming intimately familiar with the operation of and theory behind the circuit seems almost incidental to your purpose. You might as well build an HHO generator and claim that you've solved the world's energy problems. Then defy your instructor to prove you wrong.
 

Mikebits

Well-Known Member
That circuit you posted is garbage. Forget about it. Find a different project that you can copy from.
 
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