Obviously misleading performances

Needing a high gain omni antenna, I admit I bought "little hope" that an omni antenna as announcing 11dBi 30cm, this is simply miraculous for those who know the field of radio frequency. I decided that since I did not risk 3.50 ...
Not disappointed obviously. I could compare with the Inssider software and an antenna TPLINK I own making 5dBi the TPLINK gives better reception level. Anyway as usual at this price level and from China, the scam.
I can only ... deconseiller purchase a piece of wire in the SMA connector would probably give a better result :-(

To complete the picture the same tight SMA connector does not maintain the antenna right !!!