What must all amateur radio stations be capable of reliably measuring, regardless of emission mode?

Amateur radio operators are legally required to operate strictly within their allocated frequency bands to avoid interfering with other crucial radio services. For this reason, regulations mandate that every amateur station must have a reliable means of verifying its operating frequency. While monitoring Standing Wave Ratio (SWR), RF power, and modulation are all excellent practices for maintaining station health and signal quality, they are not the primary regulatory requirement for all stations. SWR and power meters help protect your equipment, but a frequency counter or calibrated dial protects the integrity of the radio spectrum. Regardless of what emission mode you are using, from CW to digital to voice, you must always be absolutely certain you are transmitting on the correct, authorized frequency.