I am interested in building a simple RF detector. One that vibrates upon the presence of RF signals would be great. I would like to use this item as part of a counter surveillance kit that i am putting together. Has anyone built one, or does anyone know where I might be able to find plans to build one? Thanks for reading.

 

Its not quite as simple as you might think :wink: . RF covers a rather wide spectrum nowadays and any detector would have to be frequency specific to detect weak signals. If your detector is too broad banded you would soon get annoyed by all the false readings from the RF noise everywhere around (if you live in a city).
Your detector would need a tuned aerial and an amplifier. A vibrating output is rather novel, most people would settle for a meter or some indicator lights to show signal strength.
If the RF is very powerful, like underneath a radio station transmitter tower, then a neon or fluorescent lamp might light up all by itself but that isn't what you had in mind, is it?

 

What I had in mind was a detector to detect frequencies in the 150 MHz range

 

check out the circuit at:

hptt://www.zen22142.zen.co.uk/Circuits/rf/bugdetector.htm

You could add a transistor driver to the circuit, and use a small pulsar vibrator from a cell phone for the vibration you want.

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Build the exotics in life, the common place comes from others.

 

trikebuilder, that link doesn't work

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thanks,
david

 

The link works if you correct the typo. In the begining of the link it is stated as being hptt. All you need to do is change it to http-and the rest of the address.

 

What about frequency higher than this? As you all know, recently there is a lot of Wireless Pinhole camera anywhere. Anyone has any circuit that would able to detect both 1.2GHz and 2.4GHz? The detector is too expensive to buy. DIY would be better and nice. Please help..... :roll:

 

1.2, 1.4 GHZ is gonna be a real pain if you dont know what you're doing. high frequencies like that are affected by EVERYTHING. For ex. if the tracks on ur PCB r 2 big or small, it'll affect frequency and/or stability.

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I'm no electronics god, i just talk too much.

 

That's the case, means no circuit available, right? And, this 150MHz detector would not be able to capture these 2 frequencies too, is it?

 

Of course there's circuits available, probably some that you can build. I was just saying that its gonna b very difficult if you totally dont know wut ur doing. if ur experienced in electronics (which you dont sound like u r), u can probly do it. im sure that theres detectors in these two frequencies that you can buy, which is your best bet. theres no way that the 150 MHZ would be able to pick up these two frequencies.

You can try building this circuit here, if you connect it 2 a voltmeter, it will show voltage, the diode has to be germanium type (at least thats wut it said on the website) u might be able to use something else (but dont quote me on that) i didnt put the cap on cuz @ the time i didnt have one but the circuit still works. i think its there to filter out power lines frequencies (60 hz here in america). gnd doesnt have to be connected to anything, its there for better sensitivity if youre testing out an RF circuit. put ur voltmeter on a low voltage setting, like mv.

I think that this circuit should work w/ high frequencies. dont build it until someone verifies this cuz im not sure. the thing that im not sure about is if the diode has to be high frequency. i could look this up but am 2 lazy. if this circuit will work, you could probly make an amplifier for it or something, ill let someone else tell you about that. hope this helps

Attached Images

simplest_rf_probe.gif (6.7 KB, 501 views)

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I'm no electronics god, i just talk too much.

 

You gotta have high frequency diodes. Best way to find out if it's high frequency... crank up the frequency generator and try it out. A simple DC Diode check to see if the diode works won't do it...