Analyze VDSL signal quality and noise levels along the line.
Analyze VDSL signal quality and noise levels along the line.
Hi there, I’m looking for advice on my VDSL setup. The download speed shows 80mbit, but I’m struggling to reach it consistently. There are lots of packet errors and the signal quality drops to around 7. Over time, the SNR gets worse, sometimes near 3, with many dropped packets. My line attenuation is decent at about 13.5 dB, but the SNR remains very poor. I’m wondering if changing the copper wires could help—does improving the physical connection really make a difference when the signal quality is so bad?
VDSL/ADSL performance relies heavily on two factors (others matter too, but these two are key). First, how far you are from the service point matters a lot—being farther away reduces quality. Second, interference plays a role; most homes have devices that can disrupt the signal. (1) Distance is something you can't control. The added length inside your home isn't the main problem, but its antenna-like effect does matter. (2) Interference is manageable; the cable from the provider is usually shielded until your house. Once that shielding breaks, interference starts affecting the connection. So consider using shielded cable to your modem or place it nearer to the telecom provider to minimize issues.
The issue lies in the balance between signal strength and noise levels. Even with high line attenuation, if the signal-to-noise ratio drops significantly, the SNR margin can become poor. Noise doesn’t just increase attenuation—it affects the clarity of the signal itself.
Line attenuation refers to the loss of signal strength as it travels from the source to your location. It doesn’t indicate the overall noise level, which is measured by SNR. That’s why SNR matters—it shows the ratio of useful signal to background noise.
Imagine two people 50 meters apart in a quiet room. Communication would be fine. If someone drills between them, you’ll need to shout and repeat. The sound you hear represents the SNR—the strength of the signal relative to interference.
If SNR drops below 10dB, it’s a problem. Place the modem near the provider’s point and test there. If the issue persists, contact your service provider. Otherwise, proceed with cables from that location to switches and continue.
Thank you very much for your assistance and clarification. Your tests showed the provider location accurate, yet SNR remained consistent while packet errors stayed minimal and speeds improved.
It's around 8 in ISP points in our alley, but closer to 6 to 7 on the ground floor. When reaching my apartment on the 5th floor, the SNR stays similar, though speeds decrease. The distance from the alley ISP point to my floor is about 15 meters. Are there any actual issues or is this a normal drop along the route?