Convective Season Brings Renewed Hazard To Amateurs

By Michael Fitzsimmons

As we wind down another winter season with the last of the snow and river ice to melt, we look forward to a summer season that offers longer, warmer and increasingly humid days. As the Polar and Arctic jets interact with the northward transition of the Subtropical jet during the spring and summer season, the environmental ingredients of increased moisture, instability and lift sets the stage for another convective season across the country. This becomes evident first along the Gulf Coast early in the year and then transitions northward eventually through the upper Midwest, Great Lakes and northern New England by late spring and summer. This convection can take the form of a single cell, multicell, supercell thunderstorm or squall line. The common denominator with any one of these storm types is the production of lightning.

Lightning it self can be a magnificent visible electrical discharge taking such forms as forked lightning, which exhibits downward directed branches, streak lightning consisting of a single, fairly straight channel, sheet lightning (a cloud-to-cloud discharge) or heat lightning. Another form of lightning that is considered rare but has even been observed moving down aisles within an airplane is ball lightning.

Forked Lightning Near Phoenix Radio Tower Streak Lightning Strike

Sheet Lightning Heat Lightning

The forked and streaked lightning, also known as cloud-to-ground lightning, initiates at the base of the cumulonimbus cloud or thundercloud in the form of a stepped ladder that moves toward the ground. Its formation occurs as a result of a small area of positive charges forming within the negatively charged lower portion of the thundercloud. This discharge releases electrons previously attached to precipitation particles in the negatively charged region of the thundercloud base. These electrons neutralize the small positive charge prior to moving toward the ground. As this now negative charge “steps” toward the positive charges on the earth’s surface a resulting channel is created toward higher surface based objects. A traveling spark from the ground meets the positive charges within the channel producing a highly visible lightning stroke from the ground to the cloud.

Amateur radio operators are all too familiar with this process and become aware of the implications if not taken seriously when constructing their shack and antenna farm. When trying to maximize long distance communication, a good rule of thumb is the higher the better. However, while this provides a strong DXing capability, it also provides lightning an avenue for a direct path to your amateur radio equipment. While amateurs can spend several thousands of dollars to make a clear and distinct long distance contact, sufficient protection of their equipment takes on a very high priority. If not, then their voice will usually transmit not much further than the walls that house their equipment.

Several protective modes are available and it’s up to each individual amateur radio operator to determine which piece or pieces of equipment are the most important. In most cases, the transceiver as well as the antenna equipment would be of highest priority for protection. This protection can be accomplished in a number of ways. First, several types of lightning arresters can be attached at various points along the coaxial feed line that’s connected to the transceiver. Arresters may be placed at entrance location to your shack or placed in connection between the coaxial feed line and the radio itself. Antennas should be grounded using an aluminum wire or a copper brand wire with general width of three-quarters of an inch. Extending this wire down to a five-eights inch diameter ground rod that is driven well into the ground will provide ample protection to the antenna system.

The various devices that guard against electrical surges produced by lightning strikes occurring nearby or as a result of a direct hit can come with a healthy price tag. However, by far the best protection and advice available when an electrical storm is imminent is to disconnect all antennas from the equipment and to disconnect the equipment from all power lines. Depending on the design and complexity of the shack setup, this could take an appreciable amount of time that becomes of the essence when dealing with a fast approaching individual thunderstorm or squall line. Connecting as much of the equipment as possible to a single, easily unplugged power line, such as a surge strip can save valuable time.