wifi signal is weak

i bought this model recently and unfortunatly the signal of wifi in comparison of two smartphone that i have is very weak and in a distance like 5 meter of router it doesnt found the router.what's the problem?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 1

crwdns2942205:01crwdne2942205:0:

I don't have problems connecting, just really weak

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934285:0crwdne2934285:0