The AC1200 USB Wi-Fi adapters were tested using IxChariot, a software program that measures network speeds in a reliable and consistent manner. The goal was to isolate each product's signal strength and throughput. After all, each one has similar specs on paper, and we want to know how they're differentiated. Both the 2.4GHz and 5GHz bands were tested separately. The router used for testing, an Asus RT-AC66U, has a maximum supported speed of 450 Mb/s on the 2.4 GHz band and 1.3 Gb/s at 5GHz. Not surprisingly, the actual throughput achieved was considerably less than those ceilings, since AC1200 tops out at 300/867 Mb/s.
The minimum (red), maximum (black) and average (blue) throughput on the 2.4GHz band is measured by IxChariot at five feet, 25 feet, 50 feet and 75 feet and expressed in Mb/s. In some cases, such as D-Link's adapter at 75 feet, there was a large difference between the minimum and maximum reported throughput. In the line chart showing average performance, of the four adapters tested on the 2.4GHz band, ZyXEL delivered the fastest speed across the 25- and 50-foot distances, with Netgear quicker at five feet and TP-Link faster at 75 feet.
The transfer rates at 2.4GHz were at their fastest from 25 to 50 feet away from the router, and they dropped off from five feet away (too close) or 75 feet away through an interfering obstacle. While it is intuitive that performance suffers from greater distances, it's less obvious that being too close to your router can cause issues as well. This phenomenon was reproduced by every adapter except Netgear's, and the lesson is that if you're five feet away, plug in via Ethernet rather than use a Wi-Fi adapter.
At 25 feet from the router, ZyXEL's AC240 registered a maximum of 99.2 Mb/s, followed by D-Link at 96 Mb/s, Netgear at 94 Mb/s and TP-Link at 91 Mb/s. At the same 25-foot distance, the averages reveal bigger differences. The quickest average again came from ZyXEL at 67.9 Mb/s, followed by Netgear at 60.2 Mb/s, D-Link at 43.7 Mb/s and TP-Link at 38.1 Mb/s. Moving out to 75 feet with a wall in the way, the averages dropped off quite a bit, with TP-Link at 24.4 Mb/s, ZyXEL at 21.6 Mb/s, D-Link at 17.6 Mb/s and Netgear at 10.9 Mb/s.
The test results on the 5GHz band were also revealing. The general consensus is to use this less-congested frequency when possible, even if it means less overall range. In our testing, however, better performance was achievable out to 75 feet. From 25 feet away, Netgear's offering registered an average of 268.9 Mb/s, ZyXEL hit 182.1 Mb/s, D-Link checked in at 154.6 Mb/s and TP-Link brought up the rear at 139.8 Mb/s. Clearly, that's a big advantage over 2.4GHz.
Netgear's performance advantage was apparent from 75 feet away, where it achieved a blistering 238.8 Mb/s, outperforming TP-Link at 96.3 Mb/s, ZyXEL at 86.5 Mb/s and D-Link at 58.1 Mb/s. Incredibly, the slowest transfer rate on the 5GHz band is more than two times faster than the fastest speed recorded on the 2.4GHz band.
We also looked at each adapter's signal strength on the 2.4 and 5GHz bands. The router (an Asus RT-AC66U) and PC (a Sony SVS13112FXS) we used remained constant throughout the testing at each distance and across the different Wi-Fi adapters.
From 25 feet away and on the 2.4GHz band, Netgear demonstrated the strongest signal at -37 dBm, while all the others were at -45 dBm. However, Netgear also placed third in average throughput at this distance. Looking at the 75-foot test, Netgear boasted the strongest signal at -57 dBm, besting ZyXEL with -58 dBm, D-Link at -64 dBm and TP-Link at -65 dBm. Again, these signal strengths did not correlate with throughput, as TP-Link achieved the fastest speed with Netgear in last.
At 25 feet on the 5GHz band, Netgear was the stand-out with the strongest signal at -38 dBm, while the other adapters reported -45 dBm. This was consistent with Netgear demonstrating the best performance from that distance as well.
From 75 feet away, while Netgear decisively reported the highest speed, D-Link actually had the strongest signal at -59 dBm, followed by ZyXEL at -60, TP-Link at -61 dBm and Netgear at -64 dBm.