PEPPERELL -- John Griswold has no cellphone, no television and no Internet on this particular day.
Griswold, a 59-year-old software engineer from Ayer, is sitting in a field in Pepperell's Heald Street Orchard, with about 10 other people, four dogs and a radio tower 100 feet high that is allowing him to talk with people across the United States and Canada.
The Nashoba Valley Amateur Radio Club's annual Field Days Saturday and Sunday gave members of the club the opportunity to practice their radio skills by simulating an emergency, and talking to club members all over the country who were doing the same.
"If there were an emergency event where all commercial communications means fail -- cellphones, radios, TVs, -- the only thing that works is amateur radio," Griswold said.
Amateur radio operators have helped guide the world through emergencies such as 9/11, the Haitian earthquake and the ongoing wildfires in Colorado, Griswold said.
While overuse may cause cellphone networks to fail, and natural disasters may wipe out power lines, amateur radio operators are in full control of their own operation.
"We keep our own equipment, we maintain our own stuff, so we're always ready to go," he said.
Griswold said those interested in becoming licensed to operate radios must take a test, but that the test is easy enough for anyone interested to study and pass.
"It used to be just science-type kids doing it -- engineers, technicians. Now you don't have to know Morse code to be licensed. The barriers to entry are lower," Griswold said.
Jill Galus, of Raymond, N.H., is teaching her daughter Annika, 6, how to use an amateur radio.
Galus said she was exposed to radio at a young age by her father, but became licensed after floods in New Hampshire in 2011 inspired the Girl Scout troop she leads to want to get involved.
"There are a lot of licensed Boy Scouts but you don't usually hear of the girls," Galus said. "The girls wanted to be licensed so they could help. We're prepared for the next time there's a big disaster."
Galus's father, James Youngbirg, of Tyngsboro, has dedicated most of his life to radio. A childhood hobby of operating amateur radio led him to a career in engineering, where he built radios for NASA and the military.
He said radios are capable of doing just about anything.
"There's nothing that a ham can't do," he said. "A ham puts his stuff together by himself, and if it doesn't work, he makes it work. You can make friends, there are people trying to bounce signals off the moon, you can connect your computer to your radio to exchange pictures and video."
Youngbirg said Field Day has many purposes.
"It's about getting out to try out your ability to set up in the field, it's a club social event and it's about showing the public who we are and what we do," he said.
For Youngbirg, what he does is a lifelong passion shared by many.
"Amateur as a word means I love it. That really sums it up," he said. "Amateur radio operators are interested, inquisitive, see both the use and romance of operating a radio station and still think it's magic to find a new friend on the other side of the world."
Follow Chelsea Feinstein at Twitter.com/CEFeinstein.