Electronic Eavesdropping Devices Detector

[audioguru]

Audioguru,
Wouldn't the PCB design change if I use the modification given by AN920?

You could use the same pcb if you use only the highpass filter.
Replace R7 with the coil and change the values of C4 and C5 like this:

[eplanet]

hi big duck
please tell me if i change this circuit that u show me (modified) in the top of this page exactly what happen in my circuit circuit?

[M.Omer]

Thanks. =)
Let's see if this circuit does the trick for me or not!

I have one more thing to ask, AN920 said,

Ideally we need more gain, something near 20dB+ to make the circuit more sensitive at the upper end. Another alternative is to use a simple gain-block that will have enough gain up to 2GHz. That together with zero bias schottky RF detector diodes as a voltage doubler should be sensitive enough.

By using the BFR90A at 10mA, the maximum gain we get is around 18dBs and that too around 80Mhz. Is this sufficient enough for detecting bugs or do I have to add a something else to increase the gain?

Later.

[audioguru]

hi Eplanet,
The original AM detector circuit is odd. R9 and R10 are not needed with the opamp that is used. The inverting mode of the opamp is a low impedance to the detector.

My modified circuit is a "normal' high impedance AM detector circuit and should work better with the opamp that is used.

[M.Omer]

Audioguru,
I'm in a fix regarding the PCB designing. One of my friend says that as this circuit is designed to work at high frequencies, I shouldn't make this by hand. As the lines would act as inductances and I might ruin the circuit. But, another one says that as I am not using any of the lines as inductances, I should make this one myself as it won't really matter. Tell me, does this circuit requires designing the PCB on protel (or any other software for that matter) or not?

[audioguru]

Use the pcb that is shown in the project.