Large high-power grow lights in residential areas are on the rise. These lights are typically over 1,000 Watts and employ electronics that can act as ballast or perform some other vital function. See photos for a typical such light and ballasts. All photos are courtesy of Tom Thompson, W0IVJ.
Unfortunately these lights have proven to be a notorious source of RFI to the Amateur Radio service. Based on the distances over which the noise can propagate, and tests conducted in the ARRL Lab, these devices can exceed the FCC limits by a considerable margin. Although these tests were limited to just a few samples, one light was measured to be in excess of 30 dB over the FCC limits.
Interference from grow lights has been shown to be problematic at distances of over 1,000 feet. This is well over three times the distance one might expect from a legal Part 15 or 18 device, i.e., one that meets the applicable FCC limits. In addition, they are typically controlled by a timer, cycling on and off at precise times every 12 hours or so.
Historically most reports of RFI from grow lights have been from a limited number of states, particularly those known to have legalized or decriminalized marijuana. California and Colorado, for example, are two such states. So far, the ARRL has received more confirmed complaints from these two states than all the others combined. It must be emphasized, however, that grow lights are being used for a wide variety of indoor horticulture. For example, other uses include growing indoor vegetables and household, ornamental and exotic plants.
Read Full Article: