ZTE MF637 internal parts "SmartBro Plug-It USB"

I was eager to put an external antenna to my USB modem ZTE MF637, an HSDPA/HSUPA 3.75G from SmartBro Plug-It. I found two internal antenna, one might be the GPRS/EDGE and the other one is for 3G. Though I can't determine well which antenna is 3G and the other. Both has different frequency of operation, whereas 3g UMTS is 2100Mhz and so on.

There is only one internal antenna connector, and which I think is for GPRS/EDGE only.