I heard some HAM's talking about a mode they called "whisper". I was curious so started digging around the web and found the related site, downloaded the software and started listening.
WSPR, pronounced "whisper", seems to be a beacon system. Although reading on the site some users don't want to call it that because of legal ramification, but what else do you call a system that sends a stations call, grid locator and power level on a very narrow, low power radio signal at random time intervals?
If it is not a beacon what is it? The stations do not communicate on the air, the software simply receives the signals and decodes them and automatically posts them to the web. You do not call CQ and have a conversation or echange information on air. I say if it is not a beacon, it is a one way transmission.
The site, http://wsprnet.org describes it as follows; "The Weak Signal Propagation Reporter Network is a group of amateur radio operators using K1JT's MEPT_JT digital mode to probe radio frequency propagation conditions using very low power (QRP/QRPp) transmissions. The software is open source, and the data collected are available to the public through this site."
Here is the screenshot of stations I heard on 20m with the bazooka at 20 feet on the morning of May 10, 2011.
You can visit the live map at http://wsprnet.org/drupal/wsprnet/map.