Before going into the details, we must know what really is hanuman chalisa yantra and how it is made. The yantra is the main word used to denote any device that is empowered by certain features in the whole. Here the main aspect which gives power to the hanuman chalisa yantra is indeed mool mantra. According to the vedas their are different kinds and types of mool mantras. And each mool mantra has to be uttered in perfect tone and rhyme. In short a perfect yantra is made with an empowered mool mantra which is uttered and written correctly in ideal pronunciation. The mantra which empowers the device is uttered and made perfect in certain way.