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On September 14-15, 2002, the Eastern NC MS-150 Bike Tour was held in New Bern, North Carolina. Many Central and Eastern NC ham groups came together to help make this event a huge success.
Ham assignments included driving SAG (Support And Gear) vehicles tasked
to patrolling the route, shadows for tour organizers, shadowing of
medical support, and staffing of rest stops. Hams were also stationed
in supply trucks, as well as vehicles follwing the first and last riders.
In addition
to these "canonical" support roles, we made an attempt to build on previous
years' use of APRS in order to track
critical resources and the pack of riders.
APRS Infrastructure
After a survey of the course, and based upon previous years' experience, it was determined that a digipeater would be required in order to make APRS communications reliable. The two-day tour consisted of two loops, each starting and finishing in New Bern. Day 1's course went east into low-lying Pamlico County, NC, and Day 2 took the riders west into Craven County. Clearly, a digipeater in New Bern would be convenient to both days' routes.
We secured a tower site with an extra 2m antenna several hundred feet high in New Bern willing to house the digipeater for the weekend. As the site had no AC power available, the digi would have to run on deep-cycle battery power. Some "back-of-the-envelope" figures suggested this would be viable.
"Main" digipeater equipment consisted of an Icom IC-2100H run at 55W, Kantronics KPC-3 (v8.2), and a 100 A-h deep-cycle wet cell battery. On Day 2, the power level of the digipeater was dropped to 10W due to concerns over battery life.
During our survey, we noted that coverage on Day 1 dropped off toward the outer reaches of the course. Pamlico County is fairly flat (generally lower than 10' ASL), and has fairly dense vegetation throughout. It was decided that we would deploy a portable digipeater at one of the rest stops on Day 1.
Our portable digipeater consisted of a 40' portable guyed mast with
a 2m/440 vertical dipole, and a Kenwood D700a mobile rig as the
radio and digipeater. Both 10W and 50W power levels were used.
On both days, NCS had good visibility to the vehicles on the course with trackers. The tactical calls being tracked included Doctor, Supply 1, Supply 2, First Rider, Last Rider, two SAGs, SAG Control, and Robin (tour official.) Each tracker was set to beacon every 1-2 minutes.
On Day 1, I captured some data from my mobile location starting in the late afternoon. By this point, most of the vehicle traffic was on the second half of the course. The remote digipeater site was still in service, but was taken down shortly after data capture was started.
| The first map shows a plot of position reports that were digipeated only by the main digipeater. Each blue diamond represents the location of a tracker when its position report was received. As you can see, we had good coverage out to about 20 miles via the main digipeater. |
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This map shows positions that were received via the remote, then the main digipeater. There is a limited amount of data here, since the remote digipeater was taken out of service shortly after the data capture. Nevertheless, it does show that the two-digi system worked well. The remote digipeater was located out east, at the point labeled "Turn 14 RS 3 Lunch." |
On Day 2, the main digipeater was throttled down to 10W, and there was no remote digipeater deployed. The lunch stop, while rich in homemade ice cream, wasn't as conducive to setting up a digipeater. Pre-tour surveying showed that Craven County would probably have better coverage than Pamlico, so the need for a remote digi was diminished.
| More data was captured on Day 2, and this map plots the reports received via the main digipeater. This log data once again comes from a mobile station rather than NCS. There were points on the route where when monitoring the APRS channel, I could hear packets being digipeated, but they were too weak to decode. The main digi had good ears, but reduced power due to battery life concerns. Still, the map shows good coverage of the course. |
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Here is a .GIF animation showing the direct reception of positions from other mobile units. The received positions are shown with blue diamonds, and my own range of positions during each time period is shown in red diamonds. This is an animation of several slices of data from throughout the day. While not rigorous, it does show the relative effectiveness of mobile-to-mobile APRS communications on the course. The "Large" version displays better, but is more sluggish. |
As usual, Bob Breyer K1RCB did a great job of managing the ham radio team. Thanks to Gary Pearce KN4AQ for surveying and producing the detailed map overlays used for the event and shown in these analyses. Bruce Arnold N8UTY and his crew of NCS ops did a great job, and Bruce's assistance in pre-tour surveying is much appreciated.
