Lots of factors can affect the performance of the antenna, such as:
1. Network coverage of celcom,DiGi,Maxis (check the network coverage map from respective web sites) which in the real world is not uniform, it is patchy and can fluctuate,
2. How far away from the transmitter tower or repeater you are located,
3. Obstructions such as buildings, hills, metallic objects blocking or interfering with the other device signal such as microwave.
4. Whether it is used indoors or outdoors,
5. Extensions cables can reduce the gain of the antenna,
6. The construction of the building (brick, cement, stone buildings, steel structure will reduce signal strength); Other factors.
LTE / 4G networks use MIMO (Multiple Input Multiple Output) technology.
4G uses a technology called MIMO "Multiple In Multiple Out" where your modem uses two separate antennas at once to deliver super-fast speeds. The modem has two internal antennas each responsible for receiving one stream of data, it is absolutely crucial we have two separate external antennas. We cannot use a 'Y' patch lead or some other trick to connect both ports of the modem into one antenna, nor can we connect both external antennas into one port. It is important to know MIMO is switched on and off by the modem. The decision whether to use MIMO is negotiated with the cell tower, whereby the quality of the received and transmitted signals are assessed (a metric known as CQI). When signal strength or quality is low it's difficult for the modem to distinguish between the two data streams, so when signal levels drop below a certain threshold level, MIMO is switched off and the modem operates with only one antenna (Port 1 on Sierra Wireless modems).
For modem that have 2 antenna port, dual external antenna are recommened for best performance.!