Really Slow Wi-Fi Speeds - Nighthawk AC1900 Wi-Fi Cable Modem Router (Model C7000v2)

Why are my Wi-Fi speeds so much slower than the wired speed?

Any help in figuring out a solution would be appreciated.

Steve

Hardware: Nighthawk AC1900 Wi-Fi Cable Modem Router (Model C7000v2)

Firmware: V1.02.09. (It’s the latest version.)

ISP: Spectrum

Speed Plan: 400 Mbps

Tests below were conducted using SpeedTest.net.

Laptop Computer

Connection: Hardwired (Ethernet cable)

Distance from Router: 3 feet

Download Speed: 456 Mbps

Upload Speed: 22 Mbps

Laptop Computer

Connection: Wi-Fi

Distance from Router: 3 feet (no obstruction)

Download Speed: 21 Mbps

Upload Speed: 16 Mbps

Desktop PC (using TP-Link wireless device via USB)

Connection: Wi-Fi:

Distance from Router: 60 feet (two floors down in house between devices)

Download Speed: 65 Mbps

Upload Speed: 21 Mbps

HELP!!!!