“…7 Spontaneous fluctuations in the capacitance of varactors has also been postulated, 8 but experimental results would suggest indirectly that this is small. 9 Mr. J. D. Pearson: The papers read tonight have been in the main theoretical with some experimental verification at low frequencies. Parametric amplifiers are normally regarded as microwave devices and a great deal of work needs to be done to extend the principals in the papers to the microwave region.…”