The additional antenna port on the GX400 (EVDO and HSPA+) are for Rx Diversity. Rx Diversity is designed to improve the quality of the downlink signal by essentially enabling the device to “choose” the best available signal. Rx diversity has been shown to improve signal quality. However, many customers decide to forego the expense of the 2nd antenna and rely on one Rx signal. Rx Diversity is set to “ON” by default in ALEOS, but if you decide to not use a 2nd antenna it’s vital to change the ALEOS setting for Rx Diversity to “OFF”. This setting can be found under the “WAN/Cellular” tab in ACEmanager 4.0