Hi guys
I have some questions about LAN cables. I appreciate your answers.
- How does flat LAN cables works? Are they twisted? What is its pros and cons?
- All the CAT6 cables have the same theoretical speed but the real world speed is different. How using copper or aluminium effects on the speed?
- How does the length of cable effects on the speed?
- What is AWG and how this effect the quality of cable? Is it bad that Flat cables has lower AWG?
- Meanwhile I have a Ethernet cable CAT5 (Not 5-E) which is transferring data with 50MB/s speed. How is that possible?
1. All CAT5e, CAT6, CAT6e cables have the interior pairs twisted. They are then flattened out with a molded PVC coating pressed onto them so that they roll straight. They are exactly the same speed . . . however cable ratings are an honor system. Usually it is harder for a CAT6 or CAT6e cable in the flat form factor to certify . . . so you may not be getting what you paid for if it is from a company that is not reputable or "too good to be true".
2. Different cables, not just aluminum but even different grades of copper or windings of copper or even just the crimps on the cable can cause the following things to change. Aluminum has only two advantages over copper. It is Lighter and Cheaper. Everything else about it in respect to making cables is worse.
Here are just a few things I test for in cables at work:
a. Delay Skew, the signal takes longer to propagate in one pair vs another by a significant difference.
b. Attenuation, the cable has too much resistance and reactance. This makes the signal lose energy measured in dB.
c. Return Loss, the cable has kinks or was crimped poorly causing reflections in the signal.
d. Crosstalk, the radiation of signal or noise to the cable either from an external source (like a power line), or an internal source (like another pair in the same cable).
e. Frequency, the maximum rated hertz that the cable supports cleanly to spec. CAT5e is 100mhz, CAT6 is 250mhz, CAT6e is 500mhz.
3. The length of the cable does a few things:
a. It introduces a longer skew due to the fact that the individual pairs are twisted at different rates.
b. It introduces a higher capacitance making it harder for the NIC to detect the peaks in voltage on the line.
c. It introduces a higher impedance due to the length of the run causing additional signal loss.
d. Because of these factors additional errors are added into the signal and eventually becomes unusable. 100 meters from device to device is the rated limit for which there to be 99.9,999,999% error free signals.
4. AWG is the thickness of the copper. Thicker copper is better for signals barring extreme cases. Unless it is for very short runs avoid cables that are thinner than 24 AWG. To be truly honest . . . If a cable is not at least 24AWG it cannot be CAT5e. The thickness is one of the required properties or else the cable is falsely labeled. CAT6 calls for 23AWG with the same caveats. To be safe, only buy flat cables that list the thickness of the copper.
5. The reason behind that is distance. The biggest difference between CAT5 and CAT5e is the windings of the pairs used to reduce crosstalk. So the amount of crosstalk introduced over the short distance isn't enough to cause the link to fail. For very, very short runs you can even use CAT3 cable to achieve gigabit speeds.
