1. When you add an external antenna (tl2424b) on AP side, the signal will be more focused in one direction, so you need to tune the AP and Client's position, let them face to face, and then you might get better signal from AP in client side.

2. Wireless communication is bidirectional, if you only change the AP side with external antenna while let the client with original inside antenna, the wireless connection improvement might not be significant due to the restriction in client side.

3.Although the signal strength is very important, while it's not the only factor which will affect the speed, some other factors such as the interference will also affect the throughput. So you can try to select a more clean channel with less interference. Besides, select 20MHz as bandwidth instead of 40MHz if the interference is severe.

4.Line of sight is not enough, you need a 1[SUP]st[/SUP] Fresnel zone clearance.

Refer to FAQ for more details: http://www.tp-link.com/en/faq-907.html