Radio Orienteering

Amateur Radio Direction Finding (ARDF)

Welcome to Radio-O.  Here is how it works! We provide a radio receiver with a directional antenna, an orienteering map, a compass, and a finger stick. By pointing the antenna and listening to the signal you can determine the direction of the signal.  Using this information you navigate to the transmitter and punch in with your finger stick. Only the start and finish are marked on the map and it is important to keep track of where you are.  To qualify as finishing you must find at least one transmitter on your course and reach the finish within the time limit. To calculate results -- first; the number of assigned transmitters you found, then; your time on the course. We offer beginner through advanced courses, Regular BOK fees apply, and Pre-Registration is required.

Latest News in Radio Orienteering

February 6th, 2018

ARDF Training Week Feb 17-25th

Details for Tuesday, Feb. 20th

We had a small group in the cold fog at Schenck on Monday.  We learned that Sprints are hard!  We are going for Sprints again on Tuesday.  We will have two sets of sprints:

  • 1:00 – 5:00 Beginner’s course (instruction and equipment provided)
  • 1:00 – 2:30 pm first sprint
  • 2:30 – 3:00 pm Change course
  • 3:00 – 4:30 Second Sprint
  • 5:00 pm pick up beginner’s course


We have plenty of brand new high quality receivers for you to use.
Bring your own headphones. 
(We have headphones you can use but I think you will prefer your own.)

We will have beginners instruction at every event.

Here is the week’s schedule. (Event descriptions below.)  Please register for events you plan on attending.  You can submit one form for multiple events if you want to plan ahead, or submit the form each time you plan to attend a single event if you want to stay flexible.

BOK ARDF Training Week February 17-25, 2018
  1. (required)
  2. (required)
  3. (valid email required)
  4. Check the events you are attending
  5. If you change your plans please return and remove your registration here. Be sure to check which events you want to be removed from.
  6. Please answer the question to prove you are human.

Classic 80m and 2m events consist of 5 controls.  All the transmitters are on the same frequency and each transmitter turns on for 1 minute and off for 4 minutes, then the sequence repeats.  To qualify you only need to get 1 transmitter, the beacon, and finish on time.

Sprint course has 2 sets of 5 controls.  Each set has its own frequency, and one set beeps faster.  Each transmitter is on for 12 seconds and off for 48 seconds.  You find one set, punch in at the beacon, get the second set and finish.  The beacon has its own frequency and is on continuously.

FoxOring course is a Score course, so you can take the controls in any order.  Control locations are  marked on the map, and the transmitter is within 50m of the the center of the circle. You orienteer to control location, however when you are about 50m from the transmitter you can hear the signal, and use your radio receiver to locate the transmitter without going to the circle location.  You punch in at the transmitter, not the location on the map.  (Usually there is no flag at the location marked on your map, however at this event there will be a flag at the marked location, but don’t punch in there, punch in at the transmitter.

Demonstration course: Two transmitters on different frequencies are on continuously.  Course length about 300m.

BOK has 7 high quality 80 meter receivers to loan out at the events, so if you haven’t tried it before be sure to try it out at the Open event and then attend some of the others.

Details for Monday, Feb. 19th

We will have a beginner course as well as a full Sprint course at Schenck Forest.  The event is from 2pm – 5pm.  We need to start pickup at 5:30.  The sprint course is about 1.5k, an can be completed in 15-30 minutes.  The beginner course will be about 500m and you can get a good feel for the sport and learn to use the equipment in about 15 minutes, and another 15 minutes to run the course.

February 5th, 2018

Eno River Open Event Feb. 18, 2018

Everyone is welcome to our first public orienteering event at Eno River State Park, on Sunday, 18 February. Registration will be at the Fews Ford shelter, just west of the loop parking lot at the end of Cole Mill Road.  (GPS coordinates = 36.073616, -79.007005).  IMPORTANT:  DO NOT PARK IN THE LOOP PARKING LOT.  Instead, just before getting to the parking lot, turn left (look for the BOK sign) and follow the park’s service road for approximately 200 meters.  Turn around on this road (busses can use the turn-around loop), and then park on the right (south) shoulder.  Doing this will keep us in good graces with park management, and will not significantly impact your walk to the start.  See the Figure below for a map of the parking and registration area.

If you’re coming in a group of 5 or more, please pre-register here to help streamline your registration process, and to help ensure that we print enough maps. If you’re coming solo or in a smaller group, you can optionally save a bit of time at the registration table by filling out your entry form, available here, before you come; although you do not need to notify us that you’re coming. Whether you register online or in person, everyone should turn in their entry form (also available at the event) and start their course any time between noon and 2:00. If you’re new to orienteering, please arrive in time to get signed in before attending our beginner’s class at 12:30. Make sure that you report back to the finish by 3:00, because we will begin picking up all of the check points (controls) at that time.

Radio Orienteering (ARDF amateur radio direction finding)

In addition to a full set of standard point-to-point orienteering courses, we will offer three Radio Orienteering courses.  First we will have a demonstration course for people who are interested in trying this variation of orienteering.  This short course will let you try the basics and shouldn’t take more than about 15 minutes.  In addition to the demonstration we will offer a short and medium FoxOring course.  FoxOring Radio-O courses minimise the frustrations of both Orienteering and Radio-O.  First of all it is a Score course, so you can take the controls in any order.  You navigate toward the circle marked on the map, when you are about 50m from the transmitter you can hear the signal, and you use your radio receiver to locate the transmitter which could be up to 40m from the location of the circle on your map.  We hope you will give Radio-O a try.  We have some excellent receivers for you to use.  You should bring your own headphones or you can use the ones we have.

Tentative course information:

  • Beginner (white): 1.9 km (11 controls)
  • Intermediate (yellow): 2.7 km (11 controls)
  • Advanced (orange): 3.7 km (11 controls)
  • Expert short (brown): 3.5 km (9 controls)
  • Expert medium (green): 5.2 km (8 controls)
  • Expert long (red): 6.3 km (8 controls)
  • Expert Fox Oring short score:  appx. 4 km (6 controls)
  • Expert Fox Oring medium score:  appx. 5 km (8 controls)

Unless the river level is dangerously high, competitors on the orange, brown, green, red, and FoxOring courses should plan on at least one wet foot crossing of the Eno River.  The water should not be more than calf-deep, and will come toward the end of the course.

The scale of the map for the beginner and intermediate courses will be 1:5000.  For the advanced and expert courses, it will be 1:10000.   A few notes about Eno River State Park and its new map are available from this PDF document: EnoRiver-VenueandMapNotes.  Participants on all courses except beginner (white) are advised to wear leg protection.


November 30th, 2017

80 m Radio “O” Receivers

BOK received the first four of our 80 m ARDF (Radio “O”) receivers from Vadim.  BOK will be renting these receivers at our Radio “O” events. (Bring your own headset.) I put them through a test and they are excellent.

  • They are very lightweight, just under 9 ounces, which is important if you are holding it up and waving it around for an hour or two.
  • The sensitivity is excellent, I can hear my practice 50 mW transmitters from over 1k.  Typical competition transmitters transmit closer to 1 W.
  • The sense differentiation is exceptional – no volume change when you activate the sense switch when the receiver is pointing toward the transmitter and almost silent in the reverse direction.  On many receivers the difference is quite subtle.  It is even excellent close to the transmitter.  With some receivers when you are close to the transmitter the sense differentiation is lost because it is overpowered.
  • Very tight null discrimination.  When you are taking a bearing to a transmitter the signal is very quiet when you are looking through the loop, (as in the picture) and loud when you are holding the receiver sideways looking edge on to the loop.  The quiet signal, looking through the loop, is very narrow.  Just a couple of degrees off of perpendicular you get a noticeably louder signal so you can take an accurate bearing.  When you are looking edge on to the loop it is about the same volume plus or minus about 10 degrees, so an exact bearing is difficult to determine.  You would use this edge on orientation if you were far away and had a very weak signal.
  • Frequency drift is sometimes a problem with analog receivers.  This test was over an hour in cool weather and there was no drift.  This will be more critical when we test it in the summer.  Frequency drift requires that you re-tune the frequency knob from time to time.
  • Whoopie is an advanced feature on a receiver.  When the signal strength increases to a certain level you can hear a series of clicks.  As the signal increases further the clicks come faster and faster until when you are really close it is a screech.  (Waiving the receiver back and forth when you are getting close the sound goes from clicks to screeches, and thus the name Whoopee.) As you turn down the gain (volume) it will go back to being clicks again.  To set this up to measure distance you make marks on your gain knob to show where the clicks begin at different distances like 500, 250, and 100 meters.  This will give you an approximate distance to the transmitter.  Since different transmitters have different power outputs you need to calibrate your marks when you are using different transmitters.  This is why at major events there is always a practice period for people to experience the characteristics of the transmitters that are being used.  The distance is just approximate because the density of foliage, moisture on the leaves and in the air, differences in antenna setup, and topology between you and the transmitter all affect the measurement.  You also need to be certain that the frequency setting hasn’t been bumped a little or drifted.  With my 50 mW transmitters the whoopee starts at about 100 m.
  • The frequency knob is very sensitive so a tiny movement makes a big change.
  • The receiver uses a standard 9v rechargeable Li battery and has a socket for the cord that snaps to a standard Li 9v charger.  When it begins to lose power in a couple of years it will be easy to replace the battery ourselves.
  • The receivers use a standard cell phone headset.  That is a 3.5mm plug with 3 contact rings (2 black stripes).  The headsets with microphones have 4 contact rings (3 black stripes) and will not work.  When you rent one of the receivers you should bring your own headset.
October 31st, 2017

Results – Radio-O, 80m Classic, Oct-29, Carolina North Forest

Six orienteers decided to brave the threatening weather. They were well rewarded. We only had a couple short showers. This was the longest ARDF at CNF and we’ve reached the limits of this venue for classic events. We had two special participants. Imre showed up with a receiver kit he built himself and took first […]

Read More
July 10th, 2017

North Carolina International Training and ARDF Radio Orienteering Events in Asheboro, NC

North Carolina International Training and ARDF  Radio Orienteering Events in Asheboro, NC
July 24 – 28, 2017

UPDATE 7/14/17:

Monday’s training event will focus on:

  • taking accurate bearings and drawing them on the map
  • detailed map reading
  • length ~2.5 km
  • Participants will need to have a compass, marking pencils in two colors, and a map board.
  • The exercise will include FoxOring and classic 80m and 2m skills.


  • FoxOring 80m, 10 controls, 4km



  • Loop “A”, 80m 5 controls, 2km
  • At the spectator control change receiver type
  • Loop “B”, 2m 5 controls 2km

2m classic

  • designed and set by Guangdong ARDF Radiosports Club

80m classic

  • designed and set by Guangdong ARDF Radiosports Club

Everyone who is interested in Radio Orienteering is welcome to these low key events in Asheboro, NC.

We will keep the distances relatively short because of the heat and the need to be prepared for the US Champs in Ohio.

The event center will be at 1725 Gray Owl Road, in Asheboro NC.  The first day will be a training event focused on map reading and taking bearings.  The next four days will be: FoxOring, Sprint, 2 m and 80 m competitions.

Our Sister Club, the Guangdong ARDF Radiosports Club in Guangdong, China are our welcome guests and we are looking forward to this friendly international competition.

Participation costs are estimated at $10 per person per day There is no predetermined fee. Costs for the event will be shared by the participants.  All travel, lodging, and meals are the responsibility of the participants and are not included in the participation cost.  Hotels and restaurants are available in Asheboro, 15 minutes from Gray Owl.

Registration Form:

BOK ARDF Training Week February 17-25, 2018
  1. (required)
  2. (required)
  3. (valid email required)
  4. Check the events you are attending
  5. If you change your plans please return and remove your registration here. Be sure to check which events you want to be removed from.
  6. Please answer the question to prove you are human.

Joseph Huberman
President, Backwoods Orienteering Klub
Ruth Bromer
Event Directors, North Carolina ARDF Championship

Don’t miss the US ARDF Champs in Ohio the following week in Harrison, Ohio.

Event dates are 31 July to 2 Aug 2017, for the training events, and 3-6 Aug being the championship events.

Event Website: