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

April 15th, 2018

Open Orienteering & ARDF events April 21-22

On the weekend of  April 21-22, 2018 we will have an Open Orienteering event with all the courses on SUNDAY, and a Radio-Orienteering event (ARDF) on SATURDAY.

Both days will be held on the Birkhead Wilderness map starting from 1725 Gray Owl Road, Asheboro, NC  (Turn around on the gravel pad at the end of the driveway and then park on the side of the driveway as you are heading out.)

Sunday Open Orienteering Event 10:30 am – 3:00 pm

  • All 7 courses, beginner through expert will be set
    • White, beginner, 2k, 1:5000 scale 10 controls
    • Yellow, intermediate, 2.5k 1:5000 scale 12 controls
    • Orange, advanced, 3.5k 1:10,000 scale 9 controls
    • Brown, expert, 3.8k 1:10,000 scale 9 controls
    • Green, expert, 5.5k 1:10,000 scale 11 controls
    • Red, expert, 7.4k 1:10,000 scale 13 controls
    • Blue, expert, 11.8k 1:10,000 scale 20 controls
  • An introductory class to get beginners started.
  • Courses open at 10:30am and close at 3pm
  • Help picking up controls will be appreciated

Saturday Radio-Orienteering (ARDF) 10:30am and close at 4pm

  • a Classic 5 fox course about 6K in length on the 80m  band using Patrick’s transmitters.  Also a shorter 4 fox course.
  • A sprint course about 2k in length with 10 low power transmitters.
  • We have 8 receivers to rent ($5)
  • Courses open at 10:30am and close at 4pm
  • Pre-registration is required

Please remember NO PARKING IN THE TURN AROUND AREA. Only park along the side of the driveway.  The best plan is to turn around on the gravel pad at the end of the driveway and then park on the side of the driveway as you are heading out.  DO NOT DRIVE ON THE GRASS – IT IS SOFT – YOU WILL GET STUCK.

Registration For April 21 ARDF and April 22 Orienteering
  1. (required)
  2. (required)
  3. BOK Member?
  4. Choose your course.
  5. Saturday-ARDF Radio Orienteering

  6. Sunday Open Orienteering Event at Gray Owl

  7. Sunday Pizza Lunch for Members
  8. A Finger Stick is required. Do you need to rent a Finger Stick?
  9. (required)
  10. (required)
  11. (valid email required)

February 25th, 2018

ARDF Training Week(s) Feb 17 to March 4th

Illia Ivanko put on the most intense ARDF training camp in the US ever. We had 12 events over 16 days at 7 venues.  That was 6 Classics, 2 FoxOring, and 5 Sprint events. (One day we had 2 sprint courses.)  We had 6 new people try the sport and a couple of them are enthusiastic about this “new” sport.  There was general agreement that Classic ARDF is more challenging, and FoxOring is a bit less challenging than Orienteering.

BOK has another 4 ARDF events on the schedule this year and Patrick and Kelly have scheduled another 4 events for Kelly’s middle school.  We are all planning to work together to build on the existing schedule to have at least one event per month.

Vadim built 8 excellent receivers for BOK, so we had equipment to loan to the newcomers, and I believe this good quality equipment contributes to the enthusiasm of the newcomers.Everyone happy after a successful event
(Horses and the PNC Arena in the background)

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.

Report on Saturday, Feb. 17th 80 m classic at Umstead West

Our first event was a success.  We use Patrick’s transmitters and everything went off with only one tiny hitch… the beacon (the transmitter at the finish that stays on all the time) went off for a while when the antenna got disconnected accidentally.

There are two types of receivers for the 80m band.  The “loop” and the “ferrite rod”, and while they work the same way the loop type has a strong signal when it is held sideways, and the rod type picks up the strong signal when it is held frontways.  Unfortunately Harold learned on the rod type, but was using our new loop type at the event.  The unfortunate result was that while he was navigating close to the controls he kept circling the transmitter and was unable to find one.  We felt terrible that he had this frustrating experience, but his spirits were still good and he is ready to try again tomorrow.

Report on Sunday, Feb. 18th FoxOring event at Eno River

Dave Waller put on a great event open orienteering event at Eno River.  He set out a FoxOring course where you orienteer to a control circle on the map and then use your receiver to locate the very low power control within about 40 meters from the circle center.  I am very happy to report that Harold found all the controls using our new “loop” receivers after his frustrating lesson on Saturday.

Report for Monday, Feb. 19th – sprint at Schenck Forest

We had a small group in the cold fog at Schenck on Monday.  We learned that Sprints are hard!  Each receiver is only on for 12 seconds so the whole set of 5 transmitters repeat every minute.  It is difficult to locate a transmitter in 12 seconds! (But at least you don’t have to wait long for it to come on again.)

Report for Tuesday, Feb. 20th – 2 sprints at Schenck Forest

We had two sets of sprints today.  After everyone completed their sprint Illia moved the controls and we went out for a second sprint.

Report for Wednesday, Feb. 21th  Classic 80m at Schenck Forest

On Wednesday we had an excellent 4km long 80 meter Classic Radio-O event at Schenck Forest.  Afterward Illia analized our splits and routes and suggested techniques to save time and complete the course more efficiently.

Report for Thursday, Feb. 22nd at Carolina North Forest

We had another successful 80 meter classic event at Carolina North Forest.  We had our first “beginner” show up.  David Waller decided to give it a try and went out with some confidence since he had made the map.  After a successful run he returned within the time limit after finding one control and the finish – this is the requirement for a successful run.  Typical of many ARDF events we had a technical delay to the start which resulted in the last finisher returning just at sunset and the control pickup finishing in the dark.  Another problem with finishing near sunset is all the amateur radio code chatter which picks up when the propagation improves because the reflection from ionosphere picks up after sunset (and presumably Hams get home from work).

Report for Friday, Feb. 23rd at Bond Park

The sprint at Bond Park went well and taught us (again) that sprints are hard to do in the optimum order without standing around and waiting for the signal to come back in another 48 seconds (which seems a lot longer than it is).  These were very short courses so we ran them a second time to correct our original mistakes.

Report for Saturday, Feb. 24th at Umstead West

Illia set another challenging championship level 80 meter classic course.  (Note: “80 meter course” references the 80 meter frequency band, not the length of the course.)

We had perfect weather and a 6 new people showed up for their very first Radio-O course and 6 regulars came as well for a record setting 12 people at one of our training events.  Patrick’s transmitters worked flawlessly throughout the event, and Joseph used his new 20′ pole to set the beacon antenna.  With all the teaching and talking we didn’t finish up until 4pm.

Report for Sunday, Feb. 25th at Umstead South

This is getting repetitive… Illia set another champion level 80 meter band Classic course at Umstead Park.  This one set two “trick” controls (also referred to as Foxes or Transmitters).  One was in a gully by the North side of Reedy Creek Lake.  It was critical to get a good bearing to determine which side of the lake it was on because your analysis made a huge difference in your route choice.  The other difficult decision was a control that was placed just off a long stretch of straight road, just where it made a slight turn.  It was nearly impossible to tell which side of the road it was on until you were nearly at the point where it was time to run into the woods.  This could result in either going to the wrong side or waiting for the Fox to come on again.  (The 5 Foxes (transmitters) are all broadcasting on the same frequency.  They each transmit in turn for one minute and then stop while the next one begins transmitting, so it takes 5 minutes for the whole cycle to complete.)

The most satisfying part of the event was that everyone found all the Foxes including Justin and Dave who first tried ARDF (Radio-O) this week.  We all took “raincoats” for the receivers because rain was predicted, but there were only a few sprinkles.  We got wetter from sweat than rain.

Report from Thursday, March 1, 2018 at Bond Park

We had a wet Classic event at Bond Park.  The rain let up for a little while, and then got going again.  While Dave and Imre had to remove their glasses because of total fogging, Joseph’s anti fog fan hat successfully kept his glasses clear.  The course was unique because the start and finish were in the middle of the map. (They are usually at the edge or corner of a map to minimise the effect of the “exclusion zone”.

Report from Friday, March 2, 2018 at Bond Park

Back at Bond Park we had a full Sprint.  The weather was cool and windy.  Again we started in the middle, so the foxes were all around us, making for various good route choice.  The wind blew some of our antennas over so over the course of the event some of the transmitters showed no direction at all which made for some frustration.  Unfortunately technical glitches are part of the sport, and need to be taken in stride.

Illia also set up two transmitters in the 2 meter band for everyone to try out.   We are going to need more practice to build enthusiasm for this band.

Report from Sunday, March 4, 2018 at Umstead North

Our FoxOring piggybacked on the BOK Open event at Umstead North.  We had a remote start and used a subset of the Green and Red courses.  Three people found all the transmitters, the problem was when Dave was picking them up.  One of the transmitters in his pack turned on accidentally while he was locating the last fox making it impossible to locate using the receiver.  He didn’t give up, but used a brute force search pattern from the flag to finally find it.

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 […]

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