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AT&T's official 4G LTE pretty speedy in San Francisco

A speed-checking app on the LTE-ready HTC Vivid shows promise for AT&T's "real" 4G network here at CNET's headquarters.

AT&T's 4G LTE on the HTC Vivid in San Francisco
AT&T's 4G LTE is speedier on the HTC Vivid in San Francisco than it was a few weeks before.
Jessica Dolcourt/CNET

Earlier today, AT&T officially turned on its 4G LTE network in San Francisco, New York, Los Angeles, and eight other cities.

The move comes almost a month after LTE was first spotted on compatible smartphones in San Francisco and elsewhere, before AT&T had begun supporting it in full. Trials like that are not unusual for carriers.

To quickly test the speeds, I grabbed up the HTC Vivid--one of three compatible LTE phones, alongside the Samsung Galaxy II Skyrocket and the LG Nitro HD--and ran, a free app we often use to measure speed diagnostics.

Speeds were much faster on the Vivid, which often tripped and stuttered during my first speed test last monthwhen LTE was still in trial, when it wasn't peaking at download speeds of 19Mbps. This time around, download speeds ranged from 17Mbps to 25Mbps.

Tested from one location right now (the CNET office), this certainly isn't the final word in San Francisco's 4G LTE experience for AT&T. However, speeds do continue to look promising, and we'll continue to keep watch.

Of course, many factors affect network performance, including the particulars of the hardware itself and the volume of data demands at a given time, known as network load. The real test is how AT&T's 4G LTE network holds steady, or falters, further down the line, as more users snatch up the carrier's LTE-ready phones.