Most N connectors are rated to about 10GHz with the better machined stainless steel versions rated to 18GHz tops. This is because above about 18GHz the center conductor to inside shield distance is close to the point where RF can propagate in both transmission line mode and wave guide mode, causing two different paths within the coax and signals can arrive at the other end out of phase and cancel.
Above about 18GHz you have to step down the internal dimensions of the connector and go with something the size of an SMA connector, but SMA is only rated to about 18GHz so you would be using a compatible "K" connector good to 40GHz or 3.5mm good to about 34GHz or 2.92mm good to about 40GHz and all these will interface with each other mechanically. This was all covered in your Microwave 101 class, were you paying more attention with the girl in the next aisle over with the short skirt?
Otherwise good quality PL-259s can be used well above 300Mhz, it just depends on what return loss or VSWR you can live with. BTW the cool girls in class all went for the APC-7 connector.
That chart tells me that N connectors are only rated to 18MHz - I find that very hard to believe.