Few things are more frustrating than a phone call that keeps cutting out. Whether you rely on a traditional landline or a VoIP service, dropouts during calls often point to an underlying broadband issue. The good news is that with a bit of systematic testing, you can usually pinpoint the culprit without needing an engineer straight away. Let’s walk through the most common causes and the practical steps you can take at home.
Start by Isolating the Problem
Before you change any settings, work out whether the dropouts affect every call or just some. This will save you hours of guesswork.
- Does it happen on incoming and outgoing calls? If only incoming calls drop, the issue may be with your provider’s routing rather than your equipment.
- Does it happen at certain times of day? Evening dropouts often point to network congestion, whilst random times suggest a line fault.
- Does your broadband itself drop? Check if Wi-Fi disconnects or streaming stops at the same moment. If so, the problem is your connection, not just the phone.
- Try a different handset. A faulty phone can mimic a broadband dropout. Swap it for a known working one.
Test Your Master Socket and Internal Wiring
In the UK, your master socket is the first point where the phone line enters your home. For traditional landlines, it’s the best place to test whether the fault is inside your property or on the external network.
- Plug a corded phone directly into the master socket, using the test socket behind the faceplate if you have one. If the dropouts stop, the fault is likely your internal wiring or a faulty extension.
- Check that every socket has a working microfilter. A missing or broken filter can introduce noise and cause dropouts.
- Disconnect all other devices from phone sockets—satellite TV boxes, fax machines, older modems—and test again.
- For VoIP, the principle is the same: plug your phone directly into the router’s phone port or your analogue telephone adapter (ATA), with no extension leads. If calls are stable, the issue is your internal phone wiring.
Wi-Fi Interference and Signal Strength
If you use a VoIP phone over Wi-Fi, interference is a prime suspect. VoIP needs a steady, low-latency connection, and Wi-Fi is easily disrupted.
- Move the phone closer to the router. Walls, mirrors, and fish tanks weaken signal. Even a few metres can make a difference.
- Change your Wi-Fi channel. On the 2.4GHz band, use channels 1, 6, or 11. If your phone supports 5GHz, switch to that—it’s less crowded.
- Keep other devices away. Cordless phone bases, baby monitors, and microwaves can all cause interference. Move them at least a metre from your router and VoIP phone.
- Test with an Ethernet cable. If calls are flawless when wired, you’ve confirmed a Wi-Fi issue. Consider a powerline adapter or a mesh node for a more reliable connection.
Overloaded Networks and Bandwidth Priorities
A VoIP call needs only about 100 kbps of bandwidth, but it is very sensitive to latency and jitter. If your network is busy, calls will suffer even if you have plenty of raw speed.
- Identify bandwidth hogs. 4K streaming, online gaming, large downloads, and cloud backups can all cause dropouts.
- Enable Quality of Service (QoS). Most modern routers let you prioritise VoIP traffic. Look for settings that mention SIP, RTP, or “voice” and give them the highest priority.
- Limit background uploads. Photo syncing and cloud backups often use your upload bandwidth, which is usually much smaller than your download speed.
- Count your devices. Older routers can struggle with many connected devices. If you have dozens of smart bulbs, plugs, and cameras, consider a newer router.
Router Settings and VoIP Specifics
Your router’s configuration can make or break VoIP calls. A few tweaks often solve persistent dropouts.
- Disable SIP ALG. This feature is meant to help VoIP, but many routers handle it poorly, causing one-way audio or dropouts. Turn it off and test.
- Update your router’s firmware. Manufacturers regularly fix bugs that affect VoIP stability.
- Check MTU settings. An incorrect MTU can cause packet fragmentation. Try 1492 or 1400 if you suspect issues.
- Look at line stats. For traditional broadband, log into your router and check the noise margin. It should stay above 6dB. If CRC errors climb during calls, you likely have a line fault.
Gathering Evidence Before You Call for Help
If you’ve worked through these steps and dropouts persist, it’s time to contact your provider. Being prepared will help them diagnose the issue faster.
- Note the times and durations. Keep a simple log of when dropouts happen and what you were doing.
- Run a continuous ping. Open a command prompt and type ping -t 192.168.1.1 to your router, and a second window pinging a public server. If both stop, your whole connection is dropping. If only the external ping stops, it’s a broadband fault.
- Check router logs. Look for “line sync” or “DSL” disconnections. Note the times.
- Tell them what you’ve tested. Mention the master socket, wired versus Wi-Fi, and any handset swaps. Ask for a line test and, if needed, an engineer visit.
