When may amateur radio operators use their stations to notify other amateurs of the availability of equipment for sale or trade?

Amateur radio is fundamentally a non-commercial service. FCC regulations strictly prohibit operators from using the airwaves to conduct business, facilitate regular commercial transactions, or advertise general goods and services to the public. Despite this, the FCC does recognize that amateurs frequently buy, sell, and trade their own personal radio gear. You are allowed to announce the availability of amateur radio equipment for sale or trade over the air, provided the items are strictly radio-related and the activity is not done on a regular, business-like basis. A common misconception is that as long as no profit is made, any sale is fine. However, the rule focuses entirely on the nature of the equipment (it must be amateur radio gear) and the frequency of the sales (it cannot be a regular business activity), regardless of profit margins.