Why does TV interfere with WiFi?

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In my home, we get internet and TV both over an optical fibre.

The setup is, this

Optical terminator -----Router----Switch---Set top box---TV--Wii U
                           |        |
                           |        \---WiFi Access point
                           |
                           \----Set top box/PVR

All links shown are ethernet, except the links to the TV, which are HDMI. There is also a WiFi link from the access point to the Wii U and to lots of devices not shown.

Now, most of the time, the WiFi (802.11n at 2.4 GHz) works fine. It works, for example, when the PVR is recording or playing back, or even when it is both recording and playing back. It works when watching netflix via a Wii U (which is good, since the Wii U uses WiFi.)

But when watching live TV, the performance of the WiFi usually drops from about 100Mbps to about 1Mbps and often connections are dropped. I've noticed that, if I pause the TV for a few seconds and then play (so the PVR acts as a buffer), this will get the WiFi working well again.

Curiously if I connect a computer to the switch directly there is no performance problem at all. Furthermore there doesn't seem to be a problem at 5GHz, only 2.4GHz.

The TV itself is not part of the problem. I can turn the TV on or off without affecting things one way or another.

So my question is, what could be causing the WiFi performance to drop dramatically when the set top box is outputting live TV is on, but not in other circumstances?

Theodore Norvell

Posted 2015-04-22T14:44:37.983

Reputation: 121

1It sounds like you have interference try increasing the channel on the 2.4 Ghz band. – Ramhound – 2015-04-22T14:59:41.740

@Ramhound Do you mean, for example, from 1 to 11? It's currently on channel 1. (I'm in Canada, so I don't think I can go past 11.) – Theodore Norvell – 2015-04-22T16:06:49.547

You can indeed go past channel 11, oem firmware won't let you, simple solution don't use oem firmware. – Ramhound – 2015-04-22T16:09:47.117

Where is all of this equipment physically in relation to the TV? I've experienced EMI from a TV's power supply disrupting 2.5GHz signals. Consider the signal path as well as proximity to the TV. – sawdust – 2015-04-22T22:22:05.463

The router and PVR are in one room, while the switch and access point (actually one unit), the TV, the STB, and the Wii U are all quite close. I can turn the TV off and still get interference and I can watch recorded shows with no interference, so I don't think it has to do with EMI from the TV itself. – Theodore Norvell – 2015-04-23T12:46:48.757

"I can turn the TV off and still get interference" -- Now you're contradicting your original post, i.e. "when live TV is on, but not in other circumstances". – sawdust – 2015-05-04T08:24:24.217

Thanks for pointing out the poor wording. I will edit to clarify. – Theodore Norvell – 2015-05-05T01:08:10.407

Sounds like the digital program delivery to your PVR is cutting into your bandwidth. The TV can be off, but the PVR could still be retrieving content. Other than that, get yourself a wifi scanner like inSSIDer, or any of the apps in the Android/Iphone store. I use Wifi Overview Pro. Use the program to discover whether or not there's a better channel to switch to. Stay on 1, 6, or 11. – Alex Atkinson – 2015-05-05T01:46:21.477

No answers