| 41. | Geometrical acoustics is the approximate theory, which is valid in the limiting case of very small acoustic wavelengths, or very high frequencies.
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| 42. | For example, when rats are threatened, they emit very high frequency ( 20, 000 to 30, 000 cycles per second ) screams.
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| 43. | :One way to think about it is that your infrared remote control is a wireless transmitter, just a very high frequency one.
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| 44. | However, very low frequency waves would be impossible to detect and there is no credible source for detectable waves of very high frequency.
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| 45. | Vacuum tube devices dominate high power ( hundreds of kilowatts ) at very high frequency ( hundreds or thousands of megahertz ) applications.
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| 46. | Additionally, at very high frequencies ( microwave ), RF power meters still use thermal techniques to convert the RF energy to a voltage.
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| 47. | The inversion is capable of allowing very high frequency ( VHF ) and UHF signal propagation well beyond the normal radio horizon distance.
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| 48. | First, he thought in terms of generating light waves with their very high frequencies rather than radio waves with their much lower frequencies.
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| 49. | SELCAL operates on the high frequency ( HF ) or very high frequency ( VHF ) radio frequency bands used for aircraft communications.
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| 50. | All the bands mentioned in this article are in the very high frequency ( VHF ) range, which extends from 30 to 300 MHz.
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