The Internet and Radio Propagation

I wanted to share with you three web sites that I am aware of that can show you how propagation is faring on the various amateur radio bands. These propagation tools don't attempt to explain the propagation modes, such as sporadic-E, tropospheric ducting, F₂ layer skip, etc. They just present the user with a map depicting the actual propagation.

Here are the sites:

• VHF Propagation Map
• PSK Reporter
• PropNet Project

I'm going to discuss the first one in this post and leave it to a future (but soon) post to discuss the other two sites.

The VHF Propagation Map can display a map of North America, Europe, Australia, Minnesota, Missouri, or the world. I understand the emphasis on Minnesota. If you examine the URL of the site you will notice that the VHF Propagation Map is hosted on a site for a Minnesota school system. I'm not sure why Missouri gets special emphasis. The map attempts to display various 2-meter radio paths with the different color-coded swatches (for lack of a better word). Yellow colors represent shorter paths; orange a little longer, and red being the longest paths. The data behind the map is obtained from the APRS-IS system. Basically in the early days of APRS, the packet-radio system was entirely RF-based, but then the Internet became commonplace, and the data from the RF side of things was fed to the Internet. The "IS" stands for Internet System. It is all of the APRS data traveling on the APRS-IS system that makes sites such as Findu and this propagation map possible. The VHF Propagation Map site does explain that some HF data may be mixed in, but I figure the percentage of HF data is pretty low. I don't pretend to know everything about APRS, but I believe earlier on, HF (and in particular, 30-meters) was used for long-haul transmission of APRS data. The Internet does that now. Anyway, this website looks at the APRS-IS data. It knows where each station is because position is reported as part of the packet, and it knows where the packets came from that the stations heard, because the transmission path is part of the packet. The website analyzes that data and plots the map.

From a practical standpoint, the user of the VHF Propagation Map, clicks on an area of interest, such as North America. If their geographical area is covered by a yellow, orange, or red swatch or blob, they can expect enhanced communications on 2-meters. If the patch is red, they should probably be able to hit distant repeaters, or communicate long distances on SSB, or CW. During the 2008 summer sporadic-E season, I visited this site a few times. Sure enough, large sections of the eastern U.S. where covered with red criss-crossing swatches. Why not the western U.S.? This site does rely on actual APRS stations. There are sections of the country (Rocky Mountain region, Nevada, Montana, and so on) that just don't have as many amateur radio operators.

So try out this site, and when color appears over your location, fire up your radio and try to hit a distant repeater, or see how far you can talk on simplex, or get out your all-mode rig and work on picking up some more grid squares. Although this site relies on data from the 2-meter band (specifically the 144.39 MHz APRS network), you might look at the higher bands such as 222 MHz, or 430 MHz, if 2-meters starts opening.

73