ES440 LTE Performance is poor

Hello community,

i bought a SierraWireless ES440 Router
and installed an external Antenna (Dual) with 2 Cables.

The Performance is verry poor:
37M down and 10M up.

On the same antenna i installed a Huawei Router
and the Performance is much better:
48M down and 10M Up

the Firmware of the device is:
ALEOS Software Version: 4.4.2 ALEOS Build number: 005
Device Model: ES440
Radio Module Type: MC7710 Radio Module Identifier: OSM003
Radio Firmware Version: SWI9200X_03.05.24.00ap r5792 carmd-en-10527 2013/05/02 13:35:47

Anyone an idea ?