General term in the shortwave radio listening (SWL) community for frequencies between 2000 - 5000 kHz.

Far from being a wasteland, the tropical band contains a number of significant radio services. Utility stations, such as teletype and navigational systems (LORAN) provide governmental, nautical, and commercial communication. Use of radio navigational systems has declined with the advent of Global Positioning System technology.

Listeners will also find clandestine stations in two categories. First are low powered propaganda stations from international hot spots such as Afghanistan or East Timor. These stations operate on their local time, so certain regions will not be accessible during every week due to poor propagation at the receiving station. Secondly, some nations operate numbers stations, or streams of numbers transmitted by voice (usually an utterly ethereal female voice). Prevalent in the Cold War era, numbers stations are still employed by nations such as Cuba.

Finally, Central and South American broadcasters operate low power stations within the tropical band. These stations are run on a shoestring and are intended for local audiences only. Most are music stations and religious broadcasters with some propaganda stations. As a fringe benefit tropical music stations provide great entertainment and exposure to music seldom heard elsewhere.

The challenge is to log the Central and South American stations when active in local prime time. Add to the mix propagation changes and the measly 1 kW power levels of the strongest stations. For comparison, BBC World Service to Europe and the Mideast broadcasts at 500 kW or more. Tropical band DXing might be characterized as the double black diamond of SWLing.

Since broadcasters use longer wavelength frequencies, listeners will find the best listening in the Northern Hemisphere during the winter months. I suspect that the optimal season patterns in the Southern Hemisphere mirror the Northern Hemisphere, converting to summer from winter respectively. Best reception occurs during local dusk, or the grey line effect. Reception remains strong for another three hours or so, but erodes completely by local midnight. Listeners utilize computer software (such as Geoclock) to predict grey line as represented by a creeping bell curve of night's progression around the world.

Although not necessary, tabletop receivers provide for optimal tropical listening. These breadbox-sized recievers require outdoor antennas. Use your imagination when crafting antennas. Favorites include dipoles, wire arrays, and electrified "active antenna" loops for cliff dwellers. I spin my own antennas, joining them to various ancient ham radio gear and an Icom R75 modern receiver. Vacuum tube radios emit rich tone when tuned properly and with fresh tubes, but tube sets found at hamfests and elsewhere usually require much restoration.

Here's to soldering burns!

Log in or registerto write something here or to contact authors.