A PA Tuning Setting a frequency on a WS no 19

[Robert Bergeron]

( A PA Tuning .) I am new to the set . I have experience on HF , VHF and UHF aviation radio’s but zero on the No 19 set . I understand i have to set the frequency on the right dial first . Let’s take for example CHU on 3.33 or 7.85 MHz. The dial readings are very coarse but i can tune in somehow and there is a knob to turn to select 2-4 1/2 and 4 1/2 to 8 MHZ. What does the A PA Tuning stand for ? I know it’s the left dial and i am supposed to turn the variometer in conjunction with it .Somehow the signal become clearer and louder when i turn that dial . What are the readings for ? What does it do ? Sorry for the very basic questions but i am very interested of making the most of my radio truck by knowing more about it’s main purpose : Operating the radio set . Thanks .