Troubleshooting Cables

EMI: External signals that interfere with the network. Common sources include generators, motors, elevators, transformers, and fluorescent lighting. 

RFI: Same thing as EMI but with radio (I.E radio transmitters cause RFI the same way generators cause EMI)

Fixes:

•  Use fiber optic cables / shielded twisted pair cables

• Don't install cables near EMI/RFI sources

Crosstalk: Interference caused by signals within twisted pairs

Fixes:

• Twist wires into pairs at different rates

• Increase twisting frequency of the wires

Attenuation: Loss of signal strength from one cable to another.

• Longer cable = more attenuation

• Higher temp cables experiecne more attenuation than lower temp ones

• Use a repeater to regenerate the signal

Impedance: Measure of resistance within the transmission medium

•  Measured in ohms (Ω)

• All cables must be at the same level of impedance

• Choose the cables with the correct rating (50 or 75 usually) based on network type

• signals are distorted when they pass through cables of differing impedance levels

Throughput: Rate that signals are processed and delivered over a communication channel

• Each circuit module has a specified estimated throughput 

• Most modern wireless access points can run in 5g mode, 2.4g mode, or mixed mode.

• Some access points support both standards, meaning one radio channel can run 2.4, while the other can run 5.

  • You can turn off the 2.4g antenna and use the extra antenna for your 5g clients and increase throughput using MIMO 

    • MIMO is using two antennas as one, with one antenna handling transmission and one handle receiving information.

• Cheap antenna + Cheap NIC = worse throughput

• High-quality antenna + High-quality NIC = better throughput

Short: When electrical signals take a path other than intended

• Usually caused by physical damage to wires causing them to touch or otherwise be able to transfer signals to eachother 

Open Circuit: When a cut in a wire prevents the original signal from reaching the end of the wire

Miswired Cable:  caused by incorrect wire positions that prevent the original wire from transmitting what was intended.

• Using a crossover cable where you should be using a straight-through is one example

Wiremapping: matching a wire and a pin on one end with the same pin on the other end. 

• An error in wire mapping would be mapping the wire at pin 1 to pin 4, for example.

Split pair condition: is a single wire in two different pairs reversed at both ends.

• For example, if instead of the solid green wire, the solid brown wire is matched with the green/white wire in pins 1 and 2.

Incorrect termination: When an incompatible or incorrect connector is used. 

• results in reduced preformance or connection loss

Bad connector: When a damaged connector causes connectivity issues

Most network devices have hot-swappable transceivers in order to allow for interfaces tailored to different cable types, protocols, and speeds.