Walt is a farmer who has several high-tech water controllers that are connected by his Asus AC2900 router. But he needs a better range to reach the controllers that are at the extreme end. Leo says that WiFi goes about 100-150 feet. So those on the edge of that will fade out depending on the conditions. Leo thinks a mesh system would be beneficial, but Walt says that the controllers don't support MESH. Leo says that may be due to the 5GHz band. Orbi makes an outdoor router system that could work, but he'll have to make sure it doesn't connect to 5ghz. Make sure the Asus is set to 2.4Ghz first. Also, raise the router higher. Leo also suggests Walt heads over to RadioLabs.com for more tips and tricks on how to maximize WiFi Range.
From the chatroom - Turn off universal beamforming, set the channel changing to manual, and then aAC2900djust it to 20mhz. Leo recommends downloading InSSIDer, which will let him map the channels in use to determine congestion and avoid it. He can also get an external antenna to aim at those controllers directionally. He could go to WiFi 6, but it's probable the controller won't support it. But if it does, then he'll have much better range. Another option is powerline networking. It's the least expensive, and probably the one that will work.