Amateur Radio Direction Finding (ARDF) for HRH Princess Maha Chakri Sirindhorn Royal Cup was first held in 2015. The winner from each year will then host the event in the following year. The provinces that have previously organized the ARDF Royal Cup include HS3AS in Surin, HS3AU in Ubon Ratchathani, HS0AC by RAST in Chonburi, HS7AS in Suphanburi, HS2AC in Chonburi, and HS8AS in Surat Thani.

Figure 1. (Left) Krabi Deputy Provincial Governor Mr Anuwat Modepring
(Top Right) Mr Kitti Kittitornkul Member of the House of Representatives Krabi province District 1
(Bottom Right) Mr Sahongsak Pehsethong HS8IAV President of Amateur Radio Association of Krabi, HS8AK

This year, Amateur Radio Association of Krabi HS8AK co-hosted the Krabi ARDF 2024 for HRH Princess Maha Chakri Sirindhorn Royal Cup with Thailand’s regulatory body the National Broadcasting and Telecommunications Commission (NBTC). The event was held at Nongtalay Subdistrict Administrative, Muang district, Krabi province, on 24-25th February 2024. Mr Somchai Hanpakdeepatima, the Provincial Governor of Krabi province, assigned his Deputy Provincial Governor Mr Anuwat Modepring to preside over the opening ceremony. The event was led by the President of Amateur Radio Association of Krabi and Chairman of the Organizing Committee, Mr Sahongsak Pehsethong HS8IAV. Other honorable guests included Mr Kitti Kittitornkul, Member of the House of Representatives from Krabi province District 1, and Mr Sukkai Chan-on, President of Nongtalay Subdistrict Administrative Organization.

Figure 2. Krabi ARDF 2024 Organizing Committee

Amateur Radio Direction Finding (ARDF), also known as radio fox hunting, is a racing sport that combines radio direction finding with orienteering skills. It is an activity that is enjoyed by HAM enthusiasts worldwide, especially the youngsters, as the competition is held outdoor. Competitors must use their knowledge and skills about radio propagations in various environmental settings as well as the characteristics of different types of directional antennas to locate the source of the waves called Foxes. These are hidden in various locations by the organizer, often over challenging terrains. The equipment specifically utilizes the 2m frequency, 144-147MHz, that are accessible to all amateur radio licensees, as well as a topographic map and a magnetic compass to help with navigation. Those who discovers all the radio transmitters in the shortest amount of time wins.

ARDF encourages participants to keep fit and stay healthy if they want to win. It also creates an opportunity for the competitors to develop a deeper understanding about amateur radio in case they are called upon in time of emergencies or natural disasters.

Figure 3. Site of Krabi ARDF 2024 competition and the location of all 5 Foxes near Tubkaek Beach, Krabi

490 competitors from 8 different provinces in Thailand and 2 different countries joined the Krabi ARDF 2024 for HRH Princess Maha Chakri Sirindhorn Royal Cup. This included HAMs from Chonburi, Bangkok, Ranong, Chumphon, Surat Thani, Phuket, Nakorn Sri Thammarat, Songkhla, and Germany. As per the rules, HAMs from Krabi were not allowed to participate. A total of 45 teams competed in 7 different categories:
•Representatives from Amateur Radio Societies for the Royal Cup
•Club Stations
•Youth (<25 years old)
•YL
•Male, less than 50 years old
•Male, over 50 years old
•Open

Figure 4. (Left) The Organizing Committee performing a check on the equipment.
(Top Right) Start point of the Krabi ARDF 2024 competition
(Bottom Right) Team from Radio Amateur Society of Suratthani HS8AS

There were no limitations on the types of equipment used apart from the Representatives from Amateur Radio Societies for the Royal Cup Category which only allowed basic equipment including a transceiver and any type of antenna. An attenuator is optional but if used must only be the passive version only.

Figure 5. Competitors in action during Krabi ARDF 2024

Figure 6. Competitors in action during Krabi ARDF 2024

The competition was held in a humid evergreen forest near Tubkaek Beach, a mountainous area with some steep slopes. The five transmitters were arranged in a U-shape starting from Fox 1, Fox 3, Fox 5, Fox 2 and Fox 4. The finish line was located at the beachfront.

Figure 7. Competitors in action during Krabi ARDF 2024

Figure 8. Competitors in action during Krabi ARDF 2024

The results from Krabi ARDF 2024 were as follow:
•Representatives from Amateur Radio Societies for HRH Princess Maha Chakri Sirindhorn Royal Cup
　1. HS8JNF from Radio Amateur Society of Suratthani HS8AS
　2. HS8LKC from Samila Amateur Radio Society of Songkhla HS9AS
　3. E25KAD from KMITL Radio Amateur Club
•Club Stations
　1. HS8XDT from Radio Amateur Society of Suratthani HS8AS
　2. E24DMQ from E20AG Club Station 32 Bangbon
　3. E25RIV from E27AC Club Station Chonburi
•Youth (<25 years old)
　1. Khun Orawanya from Radio Amateur Society of Suratthani HS8AS
　2. Khun Saruta from Radio Amateur Society of Suratthani HS8AS
　3. Mr Chutanung Panlumlert E25BNY
•YL
　1. Mrs Oracha Phonphichai HS8PQT from Radio Amateur Society of Suratthani HS8AS
　2. E25TET from Radio Amateur Society of Suratthani HS8AS
　3. E22EEB and E23LEI from E20AG Club Station 32 Bangbon
•Male, less than 50 years old
　1. Mr Wuttipong Jakrasrisakul E29WWT from Radio Amateur Society of Suratthani HS8AS
　2. HS8XXG from Radio Amateur Society of Suratthani HS8AS
　3. E24JAT
•Male, over 50 years old
　1. Mr Pornnurak Prommas HS8KF and E29QAN from Radio Amateur Society of Suratthani HS8AS
　2. E29ODX from Radio Amateur Society of Suratthani HS8AS
　3. Bernd Höfner DL1AQ and Frederic Pepin HS0ZQO
•Open
　1. Mr Chokchai Saiyarin and E24BOM from Radio Amateur Society of Suratthani HS8AS2.
　2. HS8LDA from E20AG Club Station 32 Bangbon
　3. E20WVV and Nattanon from KMITL Radio Amateur Club

Figure 9. Mr Apichat Phonphichai HS8JNF from Radio Amateur Society of Suratthani HS8AS wins HRH Princess Maha Chakri Sirindhorn Royal Cup for Krabi ARDF 2024 competition

The Krabi ARDF 2024 would like to thank the Chief Judge HS8FFH from ARDF Thailand, Competition Site Manager Mr Anothai Burinkul HS8FLU, and President of Amateur Radio Association of Krabi Mr Sahongsak Pehsethong HS8IAV.

Figure 10. Krabi ARDF 2024 Award Ceremony for the winners of different categories

An interview with the winner of Amateur Radio Direction Finding (ARDF) HRH Princess Maha Chakri Sirindhorn Royal Cup, Mr Apichat Phonphichai, HS8JNF:
“Use the lessons learnt from previous mistakes and experience as the driving force to success. All the time I had spent practicing ARDF, both inside and outside the competitions, made me realize that the readiness of my equipment, my physical strength, and all the technicalities involved are all extremely important if I wanted to succeed. The site of Krabi ARDF 2024 is hilly with steep incline especially at the start so one must be fit to tackle the routes. That big climb alone used up a lot of energy. When I switched on my radio transceiver, the signals from all transmitters from Fox 1 to Fox 5 came in very strong. Fox 1 was located on the right-hand side of the route. At the same time, the signal from Fox 2 was also very strong when the receiving antenna was pointed to the left-hand side of Fox 1. However, when I switched on the attenuator and changed the frequency, the signal was very poor unlike Fox 3 which still came in strong, so I set off for Fox 3 transmitter. From there, when I altered the direction of the beam antenna and increased the attenuator, the signal from Fox 5 was the strongest. From my previous experience, I figured out that the Organizing Committee did not place the transmitters in sequential order from Fox 1 to Fox 5, so then I started to hunt for Fox 2 and Fox 4. Once all the transmitters were found, I figured out that the transmitters were arranged in a U-shape with alternating left-right positioning. Using an attenuator and the technique of adjusting the frequency allowed us to check the strength of the signal and predict the distance of each transmitter. No matter which sports, you can only succeed with regular practice.”

Figure 11. Mr Sahongsak Pehsethong HS8IAV President of Amateur Radio Association of Krabi, HS8AK, passing on the ARDF competition flag to a representative from Radio Amateur Society of Suratthani HS8AS where the next ARDF competition will take place

Figure 12. A group photo of all participants at the Krabi ARDF 2024 competition

Lastly, the author would like to thank Mr Chokchai Saiyarin HS8XKL and Amateur Radio Association of Krabi HS8AK for all the information and pictures provided.