By Stan Horzepa, WA1LOU
Contributing Editor

This week, Surfin’ visits a website where a map reveals the real-time status of the VHF band.

One website that I visit at least once a day -- and usually many times per day -- is NG0E’s VHF Propagation Map, which displays current VHF band openings during the past hour.

The website is simple to use. On a Google map (in a user-selectable terrain or satellite view), the website displays color-coded footprints of the paths of unusual propagation: The hotter the color, the longer the path.

Zooming in and out of the map changes what the map displays. For example, when the map displays the whole continental US, only the longer propagation paths are visible; however, zoom in to display a narrower region of the US and the shorter propagation paths appear. A quick glance at the map shows you immediately what is going on. What could be easier? But theres more!

Mouseover a footprint, and the map displays the call sign of the station experiencing the unusual propagation. Click on the call sign, and the website displays a table that details the propagation data. Click on the footprint, and the map displays the path between the stations experiencing the unusual propagation.

So, how does the website come up with this information?

According to Jon Harder, NG0E, who is responsible for the site, “This map shows actual radio propagation from stations operated near 144 MHz. It uses data gathered by Automatic Packet Reporting System-Internet Service (APRS-IS) from packet stations in the Amateur Radio Service. The map is created using positions (latitude and longitude) reported by nodes in the packet radio system and the hops from node to node that the data travels. By correlating the hops with the position of each end of the hop, the distance can be inferred.”

NG0E adds that in the evening, more than 150 users are typically tuned in watching the map. So join them and check out this excellent tool for yourself.

Until next time, keep on surfin’!

Editor’s note: Stan Horzepa, WA1LOU, likes maps. To contact Stan, send e-mail or add comments to the WA1LOU blog.