(HP-67) Waveguide Cutoff

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An excerpt from Quickly now, where does waveguide cutoff occur?, Calculator Corner (HP-67/97), Microwaves (magazine) DEC 1979 (pgs. 70-72,74)

"The programs presented here use a standard Hewlett-Packard Pac routine called Calculus and Roots of f(x), to compute the cutoff wavelengths of all TEmo modes in single and double ridged waveguides. They also determine the fundamental mode characteristic impedance's of the guides at an infinite frequency. The standard routine to calculate the roots of the transverse resonance conditions occupies the first 112 steps in both programs.
These programs have the features described in the standard Pac manual. That is, the designer can opt for the pause function to see the routine converge. The value of the resonance condition, as well as the first derivative, can be obtained for any input value of λ⒞ the cutoff frequency. This latter feature is helpful in the search for roots and their identification. Typically, the accuracy of these prograrms is ±2 percent if certain restrictions. that will be outlined later, are followed."

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