Transmitter selector switch (audio control panel) - #1 or #2.
Off-volume control - Turn clockwise, set volume as required.
Frequency selector - Set desired frequency.
Fly aircraft to a point 40 nautical miles away from test station.
At 40 nautical miles, maintain communication with test station each 10° while flying a 360° flat turn
(not to exceed 5° bank). Communication should be uniformly loud and clear through these tests.
Repeat procedure for frequencies in low, middle and high ranges
*7. HF radio set - Check as follows.
Transmitter selector switch (audio control panel) - #4.
Mode selector (HF control panel) - Set desired operating mode.
Microphone switch - Press momentarily and wait for antenna coupler to tune. A 1000 Hz tone will
be heard in the headphones until tuning is complete. Tuning time should not exceed 30 seconds.