RTK Kit accuracy question

Trying out the RTK kit but the accuracy (Repeatability) seems to be in 10+ metre range. This is static power down and power up testing with base being started each time about 1 min before the rover position is. The setup is on standard tripods so was expecting some noise (2m so there is a sway) but that can only explain minor errors.

Reading 1

Lat: 1.459331 N

Lon: 103.835830 E

Alt: 25 m

Sats: 41

HDOP: 0.5

RTK Float

Reading 2

Lat: 1.459370 N

Lon: 103.835853 E

Alt: 16 m

Sats: 43

HDOP: 0.5

RTK Float

Reading 3

Lat: 1.459384 N

Lon: 103.835845 E

Alt: 17 m

Sats: 42

HDOP: 0.5

RTK Float

Not sure of the reason. Should I buy a different antenna? 

Product: https://www.dfrobot.com/product-2970.html