Hi Gordon_1, in the case of trying to pick up signals, I think the receive sensitivity of your device is more important than the transmit power. If the new 15dBi antenna hasn't improved your reception, then either you're too far away from an AP, or your device's receive sensitivity is not very good. You might like to relocate your antenna to where it is more within line-of-sight of your nearest AP, or try a directional (grid) antenna for this purpose. You might also like to check if there is a driver or firmware upgrade for your device itself.