Somehow we got on 2.4GHz - my router is dual band and the device that is having trouble uses 5.8GHz 802.11ac. As does my ipad - which works all the way out in the back yard by my pool. Problem is most like in the device - the Roku Stick, which is a little dongle that plugs in to the HDMI port on the TV, It's only slightly larger than a classis old USB memory stick - yet in that volume incorporates 802.11AC plus 2.4GHz (maybe) something for the remote control (definitely an RF remote - not sure what frequency) along with the DSP chip that can decode most any video and audio stream. And has at least some general purpose CPU power to run the user interface. It has no option for an external antenna - what is has can't be more than a basic trace on the board sort of thing. Relative to the router, it's behind the mass of the tv - when the tv was on the other side of the room, the Roku was on the side of the TV directly facing the room where the router is located - nothing but the interior wall between them, and it worked great. The TV just helps things along by having 2.4GHz 802.11g built in - it connects fine. I shouldn't have any 5.8Ghz interference in the house - no cordless phones on any frequency, the neighbors closest to the side of the house with the tv do not have any sort of wifi, and the next closest neighbor (that is broadcasting their SSID anyway) is at 2.4GHz and I am far enough away that I can only get a bare minimum signal and then only if I orient my iPad or my phone just right.
Like I said - SWMBO is not likely to change the furniture arrangement around just to fix this, so my best solution is probably stop up to a fancier device like the Roku 3 and just run an Ethernet cable and run it wired. That's actually cheaper than any of the active repeaters I've seen, though I do have a place to locate one that would have direct LOS (still an interior wall in the way) to both the router and the Roku Stick. If I had poor reception out on the patio I'd probably do it, but my stuff works fine out there. I only asked because $20 worth of antennas would be the cheapest operation and RF isn't my thing. I understand some of the concept on antenna design but am in no way an expert. Outside of an outstanding op amp course, I took mostly digital courses in college.