Correction factors for slotted measuring lines at very high frequencies

The most important factor restricting the performance of slotted measuring lines at very high frequencies (v.h.f.) is likely to be the effect of mechanical irregularities on the probe pick-up, unless the line is unusually well-constructed. These irregularities set a lower limit to the standing-wave ratio which can be measured, and below this limit the standing-wave pattern is completely obscured. Impedances giving rise to standing-wave ratios above this limit can be measured, though the effect of the irregularities reduces the accuracy. If the line is not disturbed these irregularities will usually have a repeatable effect, and they can be compensated for by a simple multiplication, the multiplying factor varying with the position along the line but being constant for each position. It is shown in the present paper how these correction factors may be derived. The procedure described is somewhat lengthy, but once it has been carried out all that is involved in subsequent impedance measurements is a multiplication of each of the voltage readings by a tabulated factor.