Wi-fi

I use free wi-fi from the local library. I have a booster and am about 200 metres from the source. My Samsung laptop picks it up with ease.....but......any Macintosh computer I have tried fails to load or sometimes fails to recognise the signal at all. The wi-fi works off my smart phone with ease. Carrying them down to the library is not really convenient. Down there they work OK. Has anyone any idea on how I can boost the signal reception within the Macintosh?
Deigh
Deigh