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long distance cell phone detector

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Audioguru said:
In my post #51 I said that the collector resistor values are too high. The schematic in this thread shows 47k ohms but the original project used 4k7 that is 4.7k (10 times less) which is one reason that the simulation shows wrong voltages.
This thread has a "general purpose" transistor as the fist one but the original project uses a real RF transistor.
EDIT: The antenna is tiny so that it does not become overloaded by strong local stations. It is designed to pickup the signal from a nearby very low power FM bug transmitter.
I did not look for more differences.
Click to expand...

There was a transistor problem, I couldn't find equivalent RF transistor in the simulator, also how I didn't saw 4.7k :grin:
 

it's working now,I changed all transistors, just there is a little problem LED stopped working after about 1 minute.
999.PNG
 

The frequency response and the current gain of an incorrect transistor can mess up a real circuit the same as messing up a simulation.
You didn't "saw" the 4.7k resistors problem because it was not translated from the "down under" 4k7 way of speeking, MATE!

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Why is the simulation signal as high as 700MHz at a very low level? Why are you using the wrong transistors for the ones following the correct first RF transistor?
Use an LC for 100MHz and feed in about 1mV at 100MHz.
 

Audioguru said:
The frequency response and the current gain of an incorrect transistor can mess up a real circuit the same as messing up a simulation.
You didn't "saw" the 4.7k resistors problem because it was not translated from the "down under" 4k7 way of speeking, MATE!

- - - Updated - - -

Why is the simulation signal as high as 700MHz at a very low level? Why are you using the wrong transistors for the ones following the correct first RF transistor?
Use an LC for 100MHz and feed in about 1mV at 100MHz.
Click to expand...
Cuz I want it to work on higher frequencies.
 

The three transistors Q1, Q2 and Q3 don't even carry RF signals, they are a crude comparator working close to DC so you should use general purpose transistors in those positions.

There are four LEDs, which one stopped working?

Brian.
 

betwixt said:
The three transistors Q1, Q2 and Q3 don't even carry RF signals, they are a crude comparator working close to DC so you should use general purpose transistors in those positions.

There are four LEDs, which one stopped working?

Brian.
Click to expand...
I know, anyway they work good, LED2.
 

Assuming the transistors were in saturation mode, the current through LED2 should only be about 9mA which is well within the limit of most LEDs. If they were not in saturation, the current would be even less.

Something else caused the problem, either a bad LED or a wrong value/connection.

Brian.
 

They are so low in value that it is easier to make small inductors from wire strips or loops the manufacture them.

13nH can be made from 3 turns of 0.6mm wire with 4mm internal diameter and spread to 10mm length.

Brian.
 

betwixt said:
They are so low in value that it is easier to make small inductors from wire strips or loops the manufacture them.

13nH can be made from 3 turns of 0.6mm wire with 4mm internal diameter and spread to 10mm length.

Brian.
Click to expand...
It was really easy.
tank you.
 

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