The US operators’ spectrum grab continues, but the ongoing 600 MHz incentive auction is not the whole story – indeed, as LTE roll-outs shift towards capacity bands and three of the top carriers plan tests in millimeter wave spectrum, the obsession with sub-1 GHz spectrum is certainly easing off. Indeed, the rounds of bidding conducted so far in the 600 MHz auction have resulted in bids worth just $19.89bn, far short of the targeted total of $86.4bn, which means the total process may take some time to complete. At the end of Friday, 21 rounds had been completed with two rounds held per day. From Tuesday, this will be increased to three per day (at one time, it had been…