This Wireless RF Network Cable Tester Circuit is like an X ray for your internet wires.
It can sniff out radio frequency signals coursing through network cables like ethernet, modem or even satellite TV cables all without touching them.
This makes it super easy to check if your cables are working properly.
Simply hold the tester near the cable and it will tell you if there is a signal or not.
No more wrestling with tangled wires or unplugging everything this circuit is a lifesaver for quick and easy cable checks.
Circuit Working:
Parts List:
| Component Type | Description | Quantity | Notes |
|---|---|---|---|
| Resistors | 100k, 1k, 3.9M, 100Ω (all 1/4 watt) | 1 each | |
| Capacitors | Ceramic 0.1µF | 2 | |
| Semiconductors | IC 3140 | 1 | |
| Diode BAT43 | 1 | ||
| LED (any 5mm, 20mA) | 1 | ||
| Coil | 10 turns, 22SWG, 5mm diameter air core | 1 | (Note in diagram for coil 0.5mm mistakenly written, actual is 5mm in diameter) |
| Antenna | 1 | ||
| Battery | 9V | 1 |
Here is an ideal wireless network cable tester designed to determine the presence of an RF signal in a network cable.
This non contact tester can detect RF signals from a distance of up to two feet making it suitable for checking various signal cables such as ethernet, modem and dish TV cables.
The circuit includes an LED that lights up when RF energy is detected around the cable.
The network cable tester consists of two main parts: the front end and the signal amplifier.
The front end features an RF detector followed by a signal amplifier.
The signal detector section comprises coil L1, diode D1, capacitor C1 and resistors R1 and R2.
Coil L1 is a 5 mm inner diameter coil made of 10 turns of 22 SWG enameled copper wire, while diode D1 is a high frequency schottky signal diode.
Capacitor C1 decouples the signals to prevent interference.
The signal amplifier utilizes the IC3140 BiMOS operational amplifier known for its gate protected MOSFET inputs.
The IC has low input current requirements as low as 5pA and operates at high speed working between 5 to 36V.
When the telescopic antenna acting as the sensor, approaches the cable coil L1 detects the RF energy and diode D1 passes this energy to the inverting input of IC1.
IC1 is configured as an inverting amplifier with feedback with resistor R3 determining the level of feedback.
When IC1 receives a positive pulse, its output goes high illuminating the LED to indicate the presence of an RF signal in the cable.
Formulas:
Below are the formulas for design of resonant circuits and antennas in RF circuits:
f = 1 / 2π√LC
where,
- L is the inductance of the coil and
- C is the capacitance of the tuning capacitor.
Antenna Length for Half-Wave Dipole:
L = c/ 2f
where,
- L is the antennas length
- c is the speed of light (about 3 × 10^8 m/s) and
- f is the frequency
Bandwidth of LC Circuit:
BW = f0 / Q
where,
- f0 is the center frequency and
- Q is the LC circuits quality factor
A detailed circuit design would include further calculations and factors unique to the frequency and modulation scheme you have selected.
How to Build:
To build a Simple Wireless RF Network Cable Tester Circuit you need to follow the below mentioned assembling steps:
- Connect one end of coil L1 to the junction of resistor R1 and R2.
- Connect the other end of coil L1 to the anode of diode D1.
- Connect the cathode of diode D1 to the inverting input pin 2 of the IC3140 operational amplifier.
- Connect capacitor C1 between the output pin 6 and the inverting input pin 2 of the CA3140.
- Connect resistor R3 between the output pin 6 and the inverting input pin 2 of the CA 3140.
- Connect the non inverting input pin 3 of the IC3140 to ground.
- Connect the LED in series with a current limiting resistor between the output pin 6 of the CA 3140 and the positive supply voltage.
- Connect the positive supply voltage to pin 8 of the IC3140 and the negative supply voltage to pin 4.
- Connect the telescopic antenna to coil L1.
Note:
- Ensure that the circuit is properly assembled and all connections are secure.
- Adjust the components as necessary to achieve the desired sensitivity and functionality.
Conclusion:
To conclude, a Wireless RF Network Cable Tester Circuit is a valuable tool for quickly and non invasively checking the presence of RF signals in various signal cables.
Its ability to detect signals without direct contact with the cable makes it a convenient option for technicians and installers working with network cables.
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