O-Lynx radios are supplied with omni-directional ( signal goes in all directions equally ) 12dbi antennas. Since the O-Lynx system works at 2.4Ghz and uses a standard connector ( RP-SMA ), most antennas sold for use with WiFi equipment can also be used with O-Lynx. Being able to use standard WiFi accesories offers the possibility on increasing or decreasing the range of O-Lynx simply by combining the radios with a suitable antenna. The line of site range acheivable when using O-Lynx radios with WiFi antennas should be a lot greater than the specified Wifi range of the antenna due to O-Lynx’s different protocol.
Directional antennas offer the possibility of achieving the extra distance but keeping within transmitter output regulations of a particular country. They do this by simply ensuring the available power of the radio waves are more focused in a particular direction. Directional antennas are especially applicable to adventure races with their greater distances between controls, but also are useful where better range is required for orienteering events, and the organisers don’t have spare radios to use as repeaters.
Two directional antennas were recently tested…
The Antenna Factor ANT-2.4-YG12-N Yagi antenna.
This is a conventional yagi antenna. As shown in the photo, a pair of the antennas were set up and the antennas comfortably reached the 10.5km from the hilltop shown to the O-Lynx office on the plains below.
TP-Link TL-ANT2414A Panel antenna
TP-Link seem to supply a good range of reasonably priced antennas that are readily available through on-line computer resellers. The ANT2414 was setup the same as the yagi antennas with an O-Lynx radio at each end. Again the 10.5 km seemed to be comfortably reached.
Both antennas still send reasonable amounts of signal to the side and rear. This means these antennas are well suited to be used for the long distance routes with standard antennas forming routes off to the side to get to the actual control sites.
The next test came in the form of a real adventure race, the 2011 Staples-Rodway Cape Kidnappers Challenge. For this event both types of antenna were used with the yagi antenna reaching the initial 6km across the bay to the cape. The TP-Link antennas were then used to direct the signal back inland about about 6 km. The race transition points were monitored by O-Lynx radios fitted with standard antennas that forked off the main radio routes. Both types of radio antenna performed well, though it was noted that despite the yagi antennas offering less surface area to blow around in the wind, their extra weight did mean they weren’t as stable as the panel antennas.
While the above situations achieved good distance, how does that relate to getting through thick bush on an orienteering course ?
The 2.4Ghz frequency used by O-Lynx radios doesn’t particularly like travelling through water, which translates to the fact that trees and humans can dramatically shorten the transmission distance. However this frequency also has a lot of positives and when combined with the O-Lynx mesh system, it enables some amazing things to be achieved. At the events I have done the limitations of the 2.4Ghz band usually just means a bit more thinking about how you place repeaters to get the best coverage.
To compare the different antennas in relation to dense vegetation I did a quick test.
A pair of standard antenna were used across the dense vegetation of orchard trees at a height designed to be the worse case of the densest part of the canopy. The standard antenna reached about 100m through the trees while the panel antenna reached about 170m. Compare this with flat open ground where the standard antennas will allow radios up to 1km apart.
More testing to come …