The MTN want the limit line 1.6 for 1800mhz and 1.5 for 900mhz if u have diplexer for the (VSWR)
And the better diplexer u will not face any problem when u used it is Kathrein .
1.5 for 1800 mhz and 1.4 for the900mhz but most time i get between 1.3-1.4 and its good