Competitors in the SHKP Vertical Run for the Chest 2013 wait nervously for the signal to run up 2,120 stairs to the 100th floor of Hong Kong's tallest building. Two staff members watch monitors on a table at one side showing every floor of the International Commerce Centre.
Three men sit next to them at another table with black boxy equipment that looks like it could be components of a sound system from the 1990s. The three are ham radio operators, and more than 40 enthusiasts arestationed at every few floors to report if a participant needs medical assistance during the charity race.
The volunteer ham radio operators for the event are members of the Hong Kong Amateur Radio Transmitting Society (Harts). Its president, Sunny Chan Loy-sun, feels it is important to assist in community events, particularly when cellphone reception is unavailable, since ham radio offers continuous communication.
Chan, 63, describes the work they do in technical terms, demonstrating both his proficiency and passion for his hobby. He is proud of the history of Harts, which was established more than 80 years ago by a group of British Army officers.
"When you make radio contact with another person, you provide a written confirmation of contact called a QSL card and send it by mail. We have ones from Britain dating back to 1930," he says.
After the handover, the group of 1,000 members was renamed, with the addition of "amateur", indicating that most of its members are radio buffs.
According to the Office of the Communications Authority, there are 48 amateur radio societies in Hong Kong, all with call signs starting with VR2. Unfortunately, skyscrapers are not conducive to transmitting radio frequencies, making the hobby more challenging.
"We have to operate VHS short wave radio, which is a very high frequency, so that we can talk to people as far away as Europe and North America. But for high frequencies, the bandwidth is small, so it's quite congested," Chan says.
Annual events such as the Trailwalker require a number of volunteers who are responsible for the continuous radio network over the 100 kilometres. "We provide safety and support for the workers, volunteers and competitors. We can call in helicopters and rescue teams in case someone is lost or injured."
Although ham radio can be rewarding and fun, Chan says it is also an expensive hobby for some. They need to build their own equipment and conduct regular maintenance, which can add up to HK$10,000 a year.
Harts also maintains the Observatory's repeaters - radio receivers and transmitters in Tai Mo Shan, The Peak, Tin Shui Wai, Sai Kung and Tate's Cairn - so members must make regular trips into the hills.
"We have to hike up to these places and so we carry smaller transmitters and receivers," Chan says, opening a backpack to reveal equipment welded to a light aluminium frame.
With the cooler temperatures and drop in humidity from October to March, amateur radio buffs are at their most active in trying to contact ham operators overseas (local communication can be done daily with small hand-held radio transmitters).
A retired ambulance superintendent, Chan became interested in ham radio at the age of 20 when he studied electronics, and it soon became his hobby.
"The fun is being able to communicate with people you don't know," he says. After setting up the antennae, large transmitters and receivers, enthusiasts twist a dial on a machine much like a radio and try to find others who are searching for people to talk to.
"You have to follow radio communication protocol and each licensed person has a station code sign. Once you make contact you have to identify who you are, where you are and what equipment you're using.
"When communicating with people overseas you should speak English, and a number of people in China do speak very good English. But if the person you've contacted can't say their code sign, we stop communicating with them right away because they are not licensed and are using the network illegally."
Chan says the group focuses on promoting "the spirit of amateur radio" and training members. It holds workshops to show people how to use or maintain the equipment. He hopes to eventually set up a base on land that has been set aside by the government for non-profit associations for training.
In 2000, some members split from Harts and formed the Hong Kong Amateur Radio Communications Association.
President Ken Hau was bitten by the radio bug in 1998. "My friends got me into it because they were playing with ham radios. It's neat to meet friends on the air, not just in Hong Kong, but also in mainland China, Taiwan, the United States and Australia.
"We talk about all kinds of things and, periodically, a group of us from Hong Kong will travel to the places where we have met friends over the radio transmitter who help organise hotels and our itinerary, while locally we meet up and go hiking or have a meal together."
The association, which has more than 100 members aged from 40 to 70, is more socially inclined.
Another breakaway group from Harts is the Hong Kong Amateur Radio Association (HKARA), which was also formed in 2000 and is led by Ho Wing-leung. He was introduced to ham radio as a young boy by an uncle who worked as a technician at Hongkong Electric. Ho's fascination with the technical aspects of telecommunications eventually led to a career in information technology.
"It's like magic because, with radio communication, it's wireless," he says. "When communications are connected by wire it either works or it doesn't, but with wireless there are many factors that affect the success of a transmission." HKARA also buys equipment and makes modifications according to licensing guidelines, which the Communications Authority inspects, Ho says. His group tries to make their operations more environmentally friendly by using renewable energy sources to recharge batteries. The group has an automatic relay station at Sunset Peak on Lantau, and they must hike up every month to check on its operation. "We have to replace equipment periodically and try to improve the efficiency through enhancements," Ho says.
The association also helps out at charity events, particularly those in support of Unicef. "We can only participate in five or six events a year because it takes a lot of time to prepare for them, have enough volunteers and hold lots of meetings to co-ordinate everything. Every month we get three or four inquiries asking us to help out in events in terms of technical support or consulting, so we evaluate them on a case-by-case basis."
There are few women interested in this technical hobby, but for Parine Ho Pui-yi, 35, ham radio allows her to apply her knowledge of physics and chemistry. "I like to take things apart and see how the equipment works, more than, say, putting on make-up," she says with a laugh. Ho enjoys helping whenever the HKARA is involved in big events where there is no cellphone coverage. "It's the fastest way to communicate - we are at different checkpoints, so whoever is closest when someone is injured or has an accident will help out."
Ham radio is a fun way to meet people, she says. "About 10 years ago my friends talked about it and that's how I got into it. It's not like a phone, where you can only talk to one person at a time - you can talk to many people here and even overseas."
She began by reading about operating ham radio and got her licence about eight years ago. "I met many people who gave me opportunities to learn more about it."
This traditional form of communication is challenging because it requires knowledge of codes that are like passwords, Ho says.
"Being able to find other people also depends on the weather, if it's night or day and if there's rain - sometimes it can be good or bad," she says. "If the signals are clear enough I can reach people as far away as Canada, Seattle and Hawaii."
Conversations, however, usually involve technical matters such as the equipment and how much power they are using. "There are many more women overseas who use ham radios, but we don't talk about too many personal things - because you don't know who might be listening in!"