Costa Rica 2003

Tropical Propagation from TI5

Propagation from an equatorial region takes some getting used to. The MUF/LUF window rises and falls quite rapidly with the high sun angle that accompanies 9 degrees North latitude. I found that the gray line periods were fairly short (45-60 minutes) and that after 9:00 AM local time (15:00 UTC) the "tropical doldrums" set in, with MUF around 12-10 meters and LUF at about 17 meters. 20 was often completely dead from 1500 to 2200 UTC here with exception of trans-equatorial signals and short hops to the Carribean.

I was struck by the effect of gray line during EU sunrise (0400-0600 UTC) which produced streams of regional contacts beginning with Eastern EU and UAs and sweeping across the continent as the sun comes up. This is especially the case on 80 meters.

Here's a waking hour summary:

UTC Local 
1200-13300600-073040 and 80 hot to JA and Far East. WNA stations were runnable.
1330-15000730-090030 runnable to JA and W/VE; long path to Indian Ocean. 12 to EU and ENA. Long path to EU on 20-17-15 with substantial dual echos.
2200-24001600-180030 to EU, ENA; 40 to EU.
0000-02001800-200040/80 hot to NA;
0200-06002000-240040/80 hot to NA; EU gray line very localized batches of QSOs

Antennas and Terrain

There is no doubt I had sub-optimal angles of radiation for 20-17-15 meters, and my operating totals bear this out. I was using a multi-band antenna, the W5GI Mystery Antenna, a relative of a G5RV, mounted at about 30 feet. Also, I had a huge hill between my position and the north making any radiation angles of less than 25 degrees virtually impossible over the pole (and towards stateside).

With only high angle radiation possible to the north, it's no wonder that 40 meters, requiring higher radiation angles, was the band producing the most contacts, especially with a low-mounted antenna (quarter wave up on 40, eighth-wave up on 80!). Still, these bands produced many EU contacts!