Signal booster question

[silverdale]

A friend is using a fire tv stick in an bedroom extension but the signal keeps dropping out. If he uses it anywhere else in the house it's fine it's a black spot. He doesn't want cables and the electric running through to the extension is on a separate circuit so he can't use home plugs.
I've read conflicting views on signal boosters some saying their fine some saying load of crap most don't work, is there anything he can do or use ?

follow up he is using a TP-Link
TP-LINK TL-WPA4220 AV600 Powerline 300M Wi-Fi Extender/Wi-Fi Booster/Hotspot with Two Ethernet Ports | Ebuyer.com

Is this a homeplug and a built in WiFi booster ?

 

[kegnkiwi]

Virgin have been sending me emails recently telling me there is now an app for checking your wifi signal in your house and if it does not reach a certain standard in a certain room they will send you a booster. I have seen two emails one offering the booster for free and one offering it a £3.00 per month.