• One question that surfaces occasionally, especially following storms, is how weather affects ham radio. There are many weather-related influences that can act upon station operation, such as temperature, wind, lightning, and barometric pressure, but this topic focuses on conditions resulting from moisture, because of its conductive nature. Remember that "propagation" means how well a radio signal retains its integrity as it travels along its path. In general, moisture from weather affects HF propagation very little, VHF propagation a little more, and UHF propagation much more noticeably.
  
  Moisture-laden conditions such as rain, snow, fog, clouds, or high humidity tend to partially refract radio signals or reduce its strength, depending upon frequency, sometimes requiring you to get your antenna higher or increase your power output to maintain good communication. Under most circumstances, you will not notice a large change in transmit or receive signal strength or integrity, regardless of weather changes. But, there are exceptions.
  
  Inversion
  One of the activities many of us get involved with, is helping out with aid station communication for marathons, bike races, and other events that take us up the mountains or into canyons. And yet toward the end of any of these, as the sun is setting in the valley, one phenomenon that seems to always catch us by surprise is the effect that dusk has on 2-meter propagation.
  
  An inversion, caused by a layer of cooler air on the ground being trapped by a warmer layer above it, creates a moisture density "boundary" that actually refracts radio signals. As well as from the typical wintertime inversion, this phenomenon can be experienced as the summer sun sets, and the air closest to the ground cools faster than the air above it.
  
  During this dusk inversion, 2-meter signals originating from under the inversion boundary tend to travel farther due to tropospheric ducting, which allows the signals to repeatedly reflect off the ground and the underside of the inversion. By the same phenomenon, 2-meter signals originating from over the inversion (like from on a hill overlooking the valley floor) tend to refract off the inversion and head off into space, while very little of the signal gets through to the ground below.
  
  Wet antennas and feed lines
  When antennas get wet, iced, or blanketed with snow, they appear to be shorted out by water, but in reality they are not, because what can appear to you like a DC short is not always an AC short, and antennas function using AC. On one hand, there's no need to go to any lengths to protect your antenna from wet weather. On the other hand, you need to make sure your connectors are waterproof and will not allow any moisture to get into the coax.
  
  Other weather-related situations
  While we're talking about the weather, it might be worthwhile to mention a few other weather-related items of interest, two of which do not always involve moisture:

Trees
Because of their water content, live trees can also alter how well radio signals get from one place to another. A few trees won't affect your signal much, but a forest can partially or completely block your signal from getting very far. For most amateur frequencies, the few trees in your back yard will typically have little effect on your ability to be heard. But if you're surrounded by a dense forest, especially one covered in snow or drenched in rain water, you might find your signal to be noticeably degraded.

Wind
If your coaxial cable is free to swing in the breeze, even slightly windy conditions can result in erratic signal reports, and can even work antenna joints and connectors loose. Be sure to secure your feed lines, structures, and antennas to sturdy anchoring posts or buildings. Make sure store-bought vertical antennas have wind ratings (often labeled wind load) that can withstand your largest local gusts. Don't underestimate the power of air movement.

Lightning
Collective lightning crashes from thunderstorms many miles away can be heard on your HF receiver as atmospheric noise, and can present anything from a minor nuisance to a complete inability to communicate. Related to lightning, excess static build-up due to air movement can discharge not only on your antenna, but on nearby chain-link fences and buildings, often heard on your radio as loud static pops resembling a crackling fire.
This training is more of a heads up than how to resolve weather-related problems, due to the extra time it would take to cover all of that. The point is, most weather won't affect ham radio operation very much; just don't be too surprised if you start getting unfavorable signal reports when the sun starts setting. 

Please note that our monthly meetings have been rescheduled to take place on the first Wednesday of each month. Additionally, our testing is typically held on the first Saturday of every month. Please refer to our Calendar page for a complete listing of all upcoming events. We would like to take this opportunity to extend an invitation to all members to attend our next meeting and say hello. Your presence and support are greatly appreciated!