( ( ( ( ( ( Tilt ( ( the angle ) ( of ( the antenna ) ) ) ) ( until ( the ( signal peaks ) ) ) ) , ) then ) ( ( measure ( the angle ) ) ( with ( a protractor ) ) ) ) . )
(ROOT (S (VP (VP (VB Tilt) (NP (NP (DT the) (NN angle)) (PP (IN of) (NP (DT the) (NN antenna)))) (PP (IN until) (NP (DT the) (NN signal) (NNS peaks)))) (, ,) (RB then) (VP (VB measure) (NP (DT the) (NN angle)) (PP (IN with) (NP (DT a) (NN protractor))))) (. .)))
Tilt the angle of the antenna until the signal peaks, then measure the angle with a protractor.
(ROOT (S (NP (NP (NNP Instruments)) (SBAR (WHNP (WDT that)) (S (VP (VB measure) (NP (NP (DT the) (NN angle)) (PP (IN of) (NP (NP (DT the) (NN slope)) (PP (IN of) (NP (DT a) (NN volcano)))))))))) (VP (VBP are) (VP (VBN called) (NP (NN tilt) (NNS meters)))) (. .)))