Cov kev txhawb nqa ncaj qha rau ntawm cov pob zeb muaj zog feem ntau yog kev txhawb nqa, feem ntau siv 1/5 ~ 1/10 ntawm qhov ntev.Lub internode ntev ntawm kev txhawb nqa yog feem ntau 2m lossis 3m.