[SOLVED] Which of these cell phone detectors have high sensitivity?

[unbuildpain]

This is one cell phone detector, it only uses 4 diodes and 1 led to detect cell phone signals

This is another using a transistor and battery

Which of these cell phone detectors have high sensitivity?

 

[betwixt]

Both about the same - they might have a range of a few cm.
Consider that cell masts can detect cell phone radiation from about 20Km away and you will understand they are not at all efficient!

Brian.

 

[unbuildpain]

Both about the same - they might have a range of a few cm.
Consider that cell masts can detect cell phone radiation from about 20Km away and you will understand they are not at all efficient!

Brian.

Do they detect only cell phone radiation or any EMF emitted by any device? Is there a way to increase their sensitivity to detect radiation from few inches from a device and make them show the strength in numbers? Like milliwatts or millivolts? And what is the frequency of the radiation?

 

[betwixt]

They detect any EM radiation if it is strong enough. It is only a loop antenna with a rectifier and load (LED/Buzzer) across it.
Yes, you can make it into a field strength meter by replacing the LED with a meter measuring mA. However, if you want to calibrate it so it has some meaningful measurement you will have to be very careful about construction. Even moving the components or something nearby will make a huge difference to the meter reading. The diodes should also be capable of working at high frequencies, you can't use power rectifiers like the 1N400x series for example and using Zener diodes as in the video is pointless.

I'm not sure what you mean by "what is the frequency of radiation?" this just measures whatever is there, it doesn't produce any frequency itself. If you want to measure the frequency as well you need a counter circuit that will operate at that frequency. That can be quite a complicated task in itself, especially at cell phone frequencies. It needs special circuitry and a stable frequency source to measure against.

Brian.

 

[Audioguru]

I suspect that cell phones used in India and Pakistan in the You Tube videos posted use different radio frequencies than cell phones use in The West.

 

[unbuildpain]

I suspect that cell phones used in India and Pakistan in the You Tube videos posted use different radio frequencies than cell phones use in The West.

The same phones which are sold in the West are sold in India and Pakistan, carriers might use different frequencies.

 

[KlausST]

Hi,

Dual band, tri band, quad band....mean different frequency bands.
850MHz, 900MHz, 1700MHz, 1800MHz, 1900MHz, 2100MHz, .... the used frequency depends on country and provider.

Klaus

 

[unbuildpain]

I've constructed the one shown in the first video but mine isn't working near cell phones. I've used the same diode. I don't think an LED has any polarity, right? Only when attached in a circuit it can have a negative and positive side. But mine has an x at the end, the opposite side of LED. Could that be the problem?

 

[d123]

Light Emitting Diode = anode and cathode

Anode towards positive voltage, cathode towards ground.

You can test the LED with a 3V battery such as a coin cell to see which pin/lead is the anode and which is the cathode (it will light up right way round), if the LED is not a typical dome-shaped LED with a flat bit at the back of the 'dome' denoting cathode side, and the cathode side lead is slightly longer.

 

[Audioguru]

Of course an LED has polarity, it is a light emitting DIODE!
The diodes must be high speed 1N4148, not slow 1N400x used for 50Hz and 60Hz.
The large part inside an LED is the negative (and the case has a flat on its rim) like this:

 

[unbuildpain]

Of course an LED has polarity, it is a light emitting DIODE!
The diodes must be high speed 1N4148, not slow 1N400x used for 50Hz and 60Hz.
The large part inside an LED is the negative (and the case has a flat on its rim) like this:

The diode I bought has has blue and brown, the shop keeper gave it to us when I asked for 1N4148, is this different? The LED I have doesn't have any short pole or long pole, both poles have same length.

 

[Audioguru]

I do not know which diodes you have. They might not work at cell phone radio frequencies.
Here is another photo of an LED:

 

[unbuildpain]

Light Emitting Diode = anode and cathode

Anode towards positive voltage, cathode towards ground.

You can test the LED with a 3V battery such as a coin cell to see which pin/lead is the anode and which is the cathode (it will light up right way round), if the LED is not a typical dome-shaped LED with a flat bit at the back of the 'dome' denoting cathode side, and the cathode side lead is slightly longer.

One pole is slightly longer, I didn't even notice it.

Of course an LED has polarity, it is a light emitting DIODE!
The diodes must be high speed 1N4148, not slow 1N400x used for 50Hz and 60Hz.
The large part inside an LED is the negative (and the case has a flat on its rim) like this:

It does have a flat rim, but it is so small I missed it.

I do not know which diodes you have. They might not work at cell phone radio frequencies.
Here is another photo of an LED:

Here is a photo of the one I made. The diodes look a bit different.

**broken link removed**

 

[betwixt]

I can't see any attachment.
1N4148 usually has the characters printed on it. I have never seen one with blue and brown bands around it but as long as it is an ordinary high speed signal diode it should work anyway.

Brian.

 

[unbuildpain]

I can't see any attachment.
1N4148 usually has the characters printed on it. I have never seen one with blue and brown bands around it but as long as it is an ordinary high speed signal diode it should work anyway.

Brian.

The attachment is a photo, it was visible earlier.

But the blue band is of a lighter shade. And there is no ring in between.

 

[Audioguru]

the cathode side lead is slightly longer.

Nope. All LED datasheets and my photo in post #12 show that the cathode lead is shorter.

 

[d123]

Hi,

Nope. All LED datasheets and my photo in post #12 show that the cathode lead is shorter.

Good point ...and unfortunately, I'll still be calling the anode the cathode and vice versa ten years from now, bad neuron connection during early learning process with that one so it is hard to re-configure the pathway.

 

[unbuildpain]

So I think I got the correct diode this time, they look similar to the one in the video but even now the LED is not lighting up near a cell phone. Do the poles of the diode have to be small?

 

[Audioguru]

I think only one diode should be used. Its wires should be long enough to be an antenna at the microwaves frequencies.
The diode and LED must have the correct polarities to be in series.

 

[unbuildpain]

I'm using only 1 diode for each side, even then it is not working near cell phones. I tried it near an EMP jammer and near that it lit up. I'm starting to think the 1st video is fake. I thought maybe I soldered them wrong, so I desoldered the contacts to the LED and reversed the diodes and soldered them back, in this configuration they didn't even lit up near EMP jammer.