Washington University, St. LouisEngineering

Nehorai quoted in the New York Times

12/2/2013

By David Waldstein, The New York Times

Below is an excerpt from "Trying to Outrun the Cardinals’ Long Reach."

ST. LOUIS — About 7 p.m. Central on Wednesday, a voice will declare on a radio wave transmitted at 1120 kilohertz, “This is KMOX, the voice of St. Louis,” and millions of homes from Denver to Alabama and Louisiana to North Dakota will be able to hear Game 6 of the World Series come to life on an AM radio.

The penetrating strength of KMOX, a powerful radio station in St. Louis with a tradition of Hall of Fame broadcasters, has helped turn countless families into Cardinals fans since 1926, when it broadcast its first game.

With a 50,000-watt signal originating from a transmitter across the Mississippi River, in Illinois, KMOX is said to be heard in 44 states and as far away as the Netherlands, East Africa and Guam, spreading the gospel of St. Louis Cardinals baseball across the planet.

The signal stretches to truly remote locales only in rare, static-filled instances. But in a swath of North America, from New Orleans to Canada, the signal could be so reliable at night that an entire region became enamored of the team.

When Jack Buck died in 2002, President Bill Clinton sent a letter to Buck’s son Joe, a former KMOX broadcaster and currently Fox’s play-by-play announcer, explaining how he had listened to Jack Buck and Harry Caray doing Cardinals games on a transistor radio hidden beneath his pillow in Hope, Ark., more than 450 miles away.

“The power of that station meant so much to countless people across this country,” Joe Buck said. “People riding on tractors or sitting on the porch, it was part of the soundtrack to their summer.”

Supposedly, it still is, despite the proliferation of televisions and Internet access. But can it really still be heard clearly in other states, without the harsh accompaniment of static and interference from other stations trying to muscle in on the signal? Surely there must be some exaggeration.

To put it to the test, I set out in my rental car Sunday, the day of Game 4 of the World Series, between the Cardinals and the Boston Red Sox, and headed south, the radio tuned to 1120 AM, to see if I could I outdrive the signal before the end of the game. I even left Busch Stadium two and half hours early, wondering if, before long, the signal would deteriorate into a fuzzy, frustrating mash of crossing signals somewhere in southeastern Missouri.

What happened was a 600-mile (round trip), 12-hour, five-state radio odyssey that illustrated, if nothing else, the lasting power of the AM radio band and the usefulness of gas stations, energy drinks and coffee.

Busch Stadium,

4:30 p.m., Central

The signal for the pregame show is strong and clear as I leave the parking lot. Certainly no other baseball writer in the country is heading away from Busch Stadium at this moment. The plan during daylight is to go through the pretty farmland in Southern Illinois — staunch Cardinals territory — then cross back over the Mississippi River into Missouri to accelerate the trip on an interstate highway.

On Route 3, near tiny Red Bud, Ill., 51 miles south of St. Louis, news of Shane Victorino’s back injury is transmitted over the car speakers. The weather is clear, and the sun is starting to dip toward the horizon. This is significant. As I go over the big river on Route 150, I hear the first distinct crackles of static.

AM (amplitude modulation) signals are susceptible to interference from numerous objects, especially as they weaken away from their source.

Within minutes, along Route 51 in Missouri, the signal is virtually lost. The car is only 100 miles from the signal tower, and the radio sounds as if it is broadcasting a shower.

“This is going to be a pointless exercise,” I say to myself. “I’ll be back at Busch Stadium by the fourth inning, looking for a new story idea.”

But anyone who has fiddled with an AM radio at night understands that after the sun sets, the whole world comes alive between 535 and 1705 kHz.

AM radio waves have unique properties that allow them to travel round the globe, but their ability to stretch beyond the horizon, instead of shooting off into space, has to do with the way they interact with the upper layers of the atmosphere, called the ionosphere.

According to Professor Arye Nehorai, the chairman of the electrical and systems engineering department at Washington University in St. Louis, the sun’s rays ionize part of the ionosphere, called the D layer, during the day, and the layer reduces the strength of radio signals that hit it. At night, without the sun’s rays, the D layer effectively disappears, and the radio waves can interact more easily with the E layer, which propagates them more effectively.

“This allows the AM waves to bounce through the ionosphere at night and travel longer distances than during the day,” he said. 

Read more on http://engineering.wustl.edu/newsstory.aspx?news=7496.

 

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