@Sunshine Where is that written? I bought a T3U Plus and was scratching my head why the iPhone SSID didn't appear.... 

  @ReisePT 

Hi,

Within the retail package of every TP-Link wireless product a small slip of paper should be included that lists the operating frequencies and max output power values that apply to the product that came in that package.

I don't have an example for a dual-band USB Wi-Fi dongle (the left one in the picture came with an "EU" 2.4 GHz USB Wi-Fi dongle), but theoretically the slip that came with your T3U Plus (EU) should show a third line reading something like 5490MHz~5730MHz ..., which correlates to channels 100 - 144.

The frequency band that includes channel 149 begins at 5735 MHz.
 

I just have a quick installation manual and a CD, but even if that existed inside it should be written on the retail box, and also, should be written with the channel numbers not frequencies. Also why it doesn't support in the EU version but seems to support in the US version?

  @ReisePT 

Perhaps a representative from TP-Link can give you some good answers.

I agree that it would be a good thing if TP-Link listed all relevant specifications of each product someplace where a potential customer could read them before making the purchase.

Unlike the US, in the EU the use of the frequency band comprising channels 149 to 165 is very restricted. It could be (pure speculation on my side) that TP-Link is afraid of conflicting with the regulations, since it could in worst case result in having to recall the affected product(s), and hence decided to disable them.