The Grow Light Problem

摘要

A very cooperative manager of a hydroponic store allowed Larry Benko, W0QE, and me (Tom Thompson, W0IVJ) to test some of his ballasts and lights. Also, one grower loaned me his equipment for the day during his "lights off" period. Using a line impedance stabilization network (LISN), we measured conducted emissions 40 dB above FCC Part 18 limits. The RFI in the HF spectrum from these ballasts can easily be heard a half-mile away. These products are available from multiple vendors; some have a sort of FCC sticker, but appear to have never been tested. The RFI is of such a magnitude that common mode ferrite chokes alone do not eliminate the interference. Larry and I developed filters that decreased the RFI from S-9 +40 dB to S-5 as measured on my IC-7000 from a short distance. Recently, an employee from the local power utility company said that about half of his RFI complaints were from grow light ballasts. In my experience, the 40 meter band seems to be where that sort of RFI is the strongest.