Radiosport and Engineering at the Olympics of Ham Radio
This event involved inviting the world’s best operators to the same geographic area (in this case, the Boston area), and setting them up with identical stations to create a level playing field. In other radiosport competitions, the contestants usually try to operate from locations with advantageous HF propagation in rare countries, with favorable local terrain (hilltops instead of valleys) and use the biggest antenna systems they can install and maximum power. However, for this event we wanted to test operating skill and had to remove all the other variables.
Levelling the playing field was a big challenge. There were 59 teams invited, so we had to find 59 “equal” locations (plus a few spares) that offered each team a location with equal HF propagation characteristics. Identical antennas were installed at each site, and a power monitor was installed to verify that all stations used 100 watts maximum power. But local terrain varies considerably in New England.
We used a variety of tools to select sites. First, we visited each site to confirm that there were no hills blocking important directions – in this competition, there is a premium on contacts with stations outside the country, and Europe has the highest concentration of hams. In addition, we looked for obstructions in the direction of the rest of the United States. Some sites were eliminated for being too high above average terrain, which would give an advantage. We also listened with mobile and portable radios to verify that there were no local sources of power-line or other man-made noise.
We then used a tool called HFTA (High Frequency Terrain Assessment) to evaluate the effect of local terrain at each proposed site for its effect on HF signal takeoff angle for the exact antenna configuration we would use. This yielded some surprises and eliminated some sites based on the impact of hills and sloping terrain not readily apparent from a visual inspection.
HFTA Terrain analysis comparing vertical radiation angle towards Europe including terrain effects at one site with same antenna over ideal flat ground.
But HFTA is just a model. We took the process one step further. During one radiosport event on 2012 and one in 2013, we installed stations at most of the proposed sites and tested the sites on the air. At certain times, we directed all of the stations to point the antennas in the same direction and operate on the same frequency band for 10 minute test periods. We gathered signal-strength data from specially equipped receiving sites in Europe and the U.S. on the Reverse Beacon Network. This is a network of stations that have wideband receivers with automatic Morse Code decoders, and report every signal they can decode with the received signal-to-noise ratio. This gave us a large data set to analyze for outliers, and to compare against the HFTA model … more than 200,000 data points!
The data was interesting. In some cases the actual received signals correlated well with the predictions (Station A modeled “better” than Station “B”, and A was indeed louder than B). However, there was considerable scatter in the data, but it was all contained in a band about the same width as the model band (about +/-1.5dB about the mean).
In the end, the results showed very low correlation with the site models as we had hoped. The winning station was almost exactly in the middle of the pack from an RF performance standpoint, i.e., they had no advantage due to location but simply were the better operators.
WRTC2014 winning team (N6MJ and KL9A) at work (photo courtesy Nodir Tursoon-Zadeh)