Router transmit power: why maximum isn't always better

Many routers have a setting called transmit power, TX power or signal strength, with choices like high, medium and low or percentages. It's tempting to set it to maximum and call it done. Sometimes that's fine. Often it isn't.

The conversation has two sides

Wi-Fi is a two-way conversation. The router talks to your phone, and your phone talks back. Raising the router's power only makes one side louder.

• Your phone's transmitter is much weaker than the router's, and you can't turn it up.
• A louder router makes the phone show more bars in far rooms, and even connect there, while the router still struggles to hear the phone.
• The result: a connection that looks strong and behaves poorly, especially for uploads, calls and anything interactive. See full bars but slow Wi-Fi.

Why maximum can make things worse

• Devices cling to the loud router. With a mesh node or second access point in the house, phones stay attached to the booming main router instead of switching to the closer unit. See phone won't switch to the nearest node.
• Your own units interfere with each other. Two access points both at full power overlap more than they need to, competing on the same channels.
• Neighbors hear you more. In apartments, a louder router adds to the crowding everyone suffers from, including you. See neighbors' Wi-Fi interference.

When to turn it down

• You have mesh nodes or several access points. Lowering the main router's power, or all of them a notch, helps devices hand over at the right moment.
• You live in an apartment and your coverage already reaches every room.
• Devices near the router show strong signal but poor performance. Occasionally a very close, very loud router overwhelms a device's receiver.

When maximum makes sense

• One router, a large house, no other units. Here there's nothing to hand over to, and extra reach at the edges helps devices that are only downloading.
• Most routers ship at maximum already. Legal limits cap the actual power; the setting mostly lets you reduce it.

Change it, then check

Transmit power is a setting where intuition fails, so measure. WiFi Heatmap maps the house at the current setting, then again after lowering it a step. Look at the rooms where two units meet: if response times get steadier there, the change helped. See also how to test Wi-Fi before and after.