Let's walk through a realistic scenario. You are at Zell am See (LOWZ), an uncontrolled airfield in Austria. You have completed your preflight inspection with radios off. The engine is now running, and the alternator is generating power.
You turn on your primary COM radio (communication radio). You select the ATF (Aerodrome Traffic Frequency) for Zell am See, which is 122.8 MHz. You press the test button and hear a brief tone—good, the receiver is responding.
Next, you prepare for the radio check. You tune to 122.8 MHz. You press the microphone push-to-talk button and transmit:
Radio Check at Uncontrolled Field
Zell am See Information · OE-CDA
PILOT: Zell am See Information, OE-CDA, radio check, one-two-two decimal eight.
ZEL_INFO: OE-CDA, Zell am See, reading you four.
This confirms that:
Your transmitter is working (they heard you).
Your receiver is working (you heard them).
Your modulation is acceptable (they rated readability 4 out of 5).
Your microphone technique is reasonable.
You have now verified radio functionality and can proceed with confidence.