Over the past few months we have received numerous calls concerning abnormal interference by VHF 2-way radio system users. Interfering signals are being received at distances of up to several hundred miles or more, both by 2-way radio users and even on the FM radio broadcast band. Generally, the interference is at its worst early in the morning and diminishes considerably by late morning.
This condition in non-technical terms is known as skip or "ducting", a phenomenon that occurs when radio signals that normally pass out into space bounce off an abnormally charged ionosphere or heavy moisture particle content associated with moving weather fronts. Sun spots or solar flares are the most common cause of skip interference. Over eleven year intervals, the Sun increasingly emits unusually intense hot spots - kind of like stoking a furnace (for those who remember such things). These supercharged flares create unusually high radiation that charges our ionosphere which causes the aforementioned signal bounce. You can learn more about Sun spots at http://solarscience.msfc.nasa.gov/SunspotCycle.shtml.
The combination of a slow moving weather front coupled with escalated Sun spot activity creates the condition that can bring chaos to FM broadcasters and VHF 2-way radio users. UHF is rarely affected since higher frequencies are less likely to bounce from the abnormally charged ionosphere and/or slow moving weather fronts with high moisture content. Fortunately, this condition rarely lasts for more than a few days. Unfortunately, there is little you can do except live with it until it passes. Like most bad things (or even good things for that matter), skip don't last very long. We thought you might like to know what is happening if you have experienced this problem. Knowledge is power!