Did you know that USB and HDMI cables also have a maximum length? And do you know why? – Image and sound – Science and technology

For USB 3.0 and 3.1, this length is set at 3 meters, while for the older standard USB 2.0 it was 5 meters. For normal HDMI cables, it is 5 meters, but I can handle 15.

USB and HDMI cables have a limited length to keep data transfer quality consistent.

Many people do not realize that even USB and HDMI cables have a limited maximum length, beyond which their efficiency and signal quality decrease significantly. Why is this so and what actually happens if we exceed this length?

A bit of physics

The key to understanding the maximum length of cables like USB and HDMI is the basic physics of electrical signal transmission. When data is transmitted over a cable, electrical impulses move along the conductors inside the cable. These impulses pass from one device to another. The quality of the signal depends on several factors, such as the quality of the cable itself, the speed of data transfer and especially the length of the cable.

There are specifications for USB and HDMI cables that determine the maximum recommended length to ensure transmission quality. For USB 3.0 and 3.1, this length is set at 3 meters, while for the older USB 2.0 standard, the limiting length was slightly larger – 5 meters. This length can be extended using active cables, but they require an external power supply. The maximum length of an active USB 3.0 and 3.1 cable is 15 meters, while USB 2.0 can reach up to 25 meters. HDMI cables have an optimal length of up to 5 meters, but they can also handle three times that length – even when transmitting high-resolution images, such as 8K. However, optimal signal quality may not be guaranteed there, you have to try it in a specific place and with a specific cable.

The maximum recommended length is given by the resistance of the material through which the signal passes. If the cable were longer, the resistance would be too great, causing signal loss. Active cables with external power or USB hubs can overcome this limit by amplifying the signal.

Reduction in quality

It follows from the above that one of the main problems with longer cables is the so-called signal attenuation. This phenomenon causes the signal to gradually weaken the longer the distance it has to travel. This is particularly problematic for high-speed data transfers such as USB 3.0 or HDMI 2.0. If the cable is too long, data may be lost, the quality of the image or sound may deteriorate, or the connection may fail completely. This phenomenon is also influenced by the quality of the materials used and the data intensity of the signal. For less demanding transmissions, the cable can be longer, but poor-quality cables can cause signal interference even at shorter distances.

With USB cables, in case of signal loss, the data transfer will either be delayed or completely interrupted. HDMI cables that transmit a combination of video and audio can lose image quality, reduce resolution, or have audio dropouts if the cables are too long.

When using USB or HDMI cables to their maximum length, there are several ways to optimize their performance:

1. Use of high-quality cablev – Quality materials and construction can help minimize signal loss.
2. Active cables or signal amplifiers – Active cables can increase the transmission length up to 15 meters with USB 3.0 and HDMI, and 25 meters with USB 2.0.
3. Avoiding interference – Electrical interference from nearby devices can reduce the quality of signal transmission.

If you need to transmit data or images over longer distances, there are alternative solutions. One option is to use an Ethernet cable, which allows data to be transmitted over much longer distances without loss of quality. Optical HDMI cables are also often used to transmit images and sound over longer distances, which have lower attenuation and transmit the signal over longer distances.