NEW YORK -- David Lyle, CEO of the National Geographic Channel, has seen enough of the letters to know how they go. The writer is typically a longtime reader of the company's flagship magazine, who perhaps recalls the times he leafed through its glossy pages while perched on grandpa's knee."The second paragraph," he said, "would always be, 'So you can imagine my disappointment when ...'"Fill in the blank. Maybe the person saw the channel's documentary about escort services, or a show about a man who sculpts with a chain saw. Perhaps it was a show about gypsies, UFO hunters or people stocking up for the imminent end of the world.Every day Lyle and his executive team face the challenge of building a successful network in the era of Honey Boo Boo and Duck Dynasty without damaging a National Geographic brand that has stood for quality since the magazine was first published in 1888.The first three months of 2013 represented the network's best quarter since its launch in 2001. The National Geographic Channel averaged 554,000 viewers in prime time, propelled by Doomsday Preppers, the Wicked Tuna series about fishermen in Gloucester, Mass., and a movie dramatization of Bill O'Reilly's book Killing Lincoln."We have a lot to grow on," Lyle said. "We have just scratched the surface with the types of shows and the types of people and ideas we can explore."Toward the end of 2011, Lyle appointed Howard Owens, a founder of Reveille Productions, as the network's president and brought on Courteney Monroe from HBO as chief marketer. The station is a joint venture between National Geographic and the Fox cable networks.Before its makeover, NatGeo was a musty network that aired documentaries with "voice of God" narrators and few reasons for people to watch regularly, Lyle said.The new team's mandate was to make the channel contemporary and "add the big E -- entertainment" without alienating people, he said.Executives honed in on where the traditional National Geographic brand and a new National Geographic Channel could intersect. They feel people look to National Geographic for access to something they wouldn't normally see, often someplace compelling visually.One of the reasons that Wicked Tuna works -- aside from its great title -- is that the characters are doing what they normally do, "and our cameras happen to be there catching it," Owens said. Another popular series is Inside Combat Rescue, which follows military rescue units in Afghanistan.There clearly have been culture clashes between supporters of the National Geographic Society, the scientific and educational institution that publishes the magazine and partly owns the channel, and the National Geographic Channel."The channel has become to National Geographic what the Frankenstein monster became to Dr. Frankenstein," said Alan Mairson, a former writer and editor at the National Geographic magazine. He writes a blog, societymatters.org, that claims the channel hurts the society's reputation but is tolerated because of the money it brings in. Several people have told him they gave up their society membership because of something on the channel.The society's outgoing CEO, John Fahey, said some of the channel's past programming choices didn't help the brand, primarily because there was an attempt to emulate what other networks were doing."The channel has clearly decided that they wanted to make sure the shows are smarter shows and reflect the brand," Fahey said. "We're not quite there yet, but we are making good progress."Protecting the brand is important, but so is attracting viewers. Programmers can't look down their noses at people, he said.Fahey praised the upcoming Brain Games, which premieres Monday and puts the brain through a series of experiments and optical illusions. The returning series Locked up Abroad, which airs Wednesday, tells the story of former Vietnam War soldier Ernie Brace, a friend of John McCain who was held captive for nearly eight years.Two series in May go north as the weather heats up. Life Below Zero heads to one of nonfiction TV's favorite locations, Alaska, to explore the lives of people who live on their own in remote corners of the state. Ultimate Survival Alaska follows a group of outdoorsmen put to the test.