An amateur radio net (ham-speak for network) is an organized gathering of at least three hams on the air for a specific purpose. It is usually on a regular schedule (e.g., 9pm local on Wednesdays) and specific frequency (e.g., 146.900 repeater). Nets are organized for various reasons, usually conforming to one of two categories: hobby/pleasure and utilitarian. Nets may be impromptu and unscheduled, such as during severe weather when a net may be quickly organized, or following a local emergency or disaster.
While there are CW (Morse code) and voice (phone) nets on the HF bands, most ham nets are found on VHF/UHF repeaters to serve area organizations such as a club or emergency communication group. EmComm organizations such as ARES typically have weekly training nets so it’s likely that one is in your area.
Radio nets can be formal or informal. You are most likely to encounter formal nets which have a more structured feel.
When joining a more formal net, you are likely to hear the phrase, “directed net.” This means that one operator is in charge of the net, and this person is the net control station (NCS). The NCS is sort of a traffic cop for the net, directing who does what and when. The NCS gets the net started, keeps it orderly, manages net activities, and closes the net down when finished.
Identify yourself using the ITU phonetic alphabet when checking into a formal net. With a directed net, once stations have checked in and been acknowledged by the NCS they should not transmit again until called. If one station has something urgent or needs to speak to another operator, they call the NCS.
The directed net structure minimizes interference within the group by ensuring that only one station is transmitting at a time, at least in theory. It assumes that all stations are aware of the directed net protocol and follow it. You may hear multiple people transmitting at net check-in (ham-speak = double) but even here the NCS is in charge and should get the doubles sorted out. The system works pretty well. The best way to learn directed net protocol is to listen in on a few nets. Observe how they operate and follow their lead when you’re ready to join in.
As with all ham radio communications, legal identification is required. Give your call sign every 10 minutes during a net (typically only the NCS will talk that long) and at the end of your exchange. Your check-in satisfies the ID requirement if this is your only transmission.