Keith wrote:
"Consider a slotted line used to measure voltages for the computation of
VSWR."

O.K. I`m looking at my PRD 250-A. Its slot is about 10 inches long or
about 25.4 cm. The distance between a maximum and a minimum voltage
point in an standing wave pattern is 1/4-wavelength.

The velocity factor is not quite as high as that of free-space. This
tends to shorten the distance between maxima and minima in the slotted
line.

If you could get a good voltage sample anywhere within a 25 cm slot, you
could get one maximum and one minimum in a standing wave pattern at a
frequency where the slot was at least 1/4-wavelength, but you might have
to adjust feedline length to place the pattern in a favorable slotted
line location.

What frequency has a 1/4-wavelength of 25 cm? My calculation says: 300
MHz.

Slotted lines are called trough lines in the U.K. I believe.

SWR is more easily determined with an SWR meter or a wattmeter. These
don`t require a slotted line`s 1/4-wave or more minimum of space for
operation.

The maximum and minimum voltages on a transmission line are not as
significant as the forward and reflected powers because the difference
between these powers is the power delivered to the load and is also the
power supplied by the transmitter as the transmission line has no
storage capacity beyond that required to completely energize the line in
both directions by the traveling wave.

Best regards, Richard Hsarrison, KB5WZI