August 1, 2008

Editor's Letter: Let There Be QAM

By Jonathan Tombes

"To purify the language of the tribe" - that's the goal of both the composition teacher and poet, wrote the former U.S. Poet Laureate Donald Hall at some point in his distinguished career.

It's analogous to what editors of trade journals do, although our Managing Editor Ron Hendrickson is more plainspoken in framing our job description. "Word janitors," he says.

No offense to our contributors, but cleaning up and otherwise revising prose is what we do. Helping us in that effort is our Senior Technical Editor Ron Hranac, who reviews much of what you end up reading and who remains ever alert to the misuse of terms. Quadrature amplitude modulation (QAM) is often exhibit A in a lineup of infractions.

Hranac has good company. In a March Multichannel News column headlined "Memorize This About QAM (Please)," Leslie Ellis gave her readers a primer and instructions worth saving.

Beyond its editorial misuse, the modulation scheme itself is on my mind, if for a contrarian reason. Last year edge QAM device vendors, anticipating accelerated switched digital video rollouts, injected this category with buzz. This year it's quiet.

A little too quiet. The shift in timing–certainly at Comcast–from SDV to analog reclamation has left some things unsaid. Installation truck rolls, for one, which I've written about elsewhere. Another is the deployment of additional QAM channels.

It's not the expense. The cost of the QAM modulators that will digitize Comcast's analog lineup is a fraction the total cost of the much-discussed, digital-to-analog converter boxes. (Although we're still talking many millions of dollars.) And it's far fewer modulators than required by SDV.

There's simply going to be a subtle shakeup in the QAM domain: For instance, as much as a tenfold increase in the number of channels running off one F-connector, because of a much larger and newly spaced digital lineup. Expect more adjustments in equipment design and headend operations as this digital migration advances.

Jonathan Tombes
Editor