On Nov 9, 6:39*pm, Cecil Moore wrote:
... the Hamwaves inductance calculator provides us an easy way
of calculating that delay through the loading coil.

http://hamwaves.com/antennas/inductance.html

Assume a 10" long, 100 turn coil with a diameter of 2" wound with #18
wire. In metric, that's 254 mm long, 50.8 mm diameter, and 1.024 mm
wire. At 4 MHz, the above calculator indicates that the axial
propagation factor is 2.122 rad/m which we can convert to degrees/inch
by multiplying by 1.4554 which yields 3.088 degrees per inch. The coil
is 10 inches long so the number of degrees occupied by the coil at 4
MHz is 30.9 degrees.

If this coil is used as a base loading coil in a 4 MHz mobile antenna,
it occupies ~30.9 degrees of the antenna. A 7 foot whip occupies ~10.2
degrees at 4 MHz. The antenna, at resonance, is known to be 90 degrees
long. So the phase shift at the coil to whip junction has to be ~48.9
degrees assuming resonance at 4 MHz.

For an electrical 1/4WL base-loaded antenna, e.g. an HF mobile
antenna, there exist three phase shifts that add up to 90 degrees. The
phase shift through the coil plus the coil to whip junction phase
shift plus the phase shift through the whip have to add up to 90
degrees. For a center-loaded antenna, there are four phase shifts that
must add up to 90 degrees. The phase shift at the base to bottom of
loading coil junction is negative. That's why we need more inductance,
i.e. more phase shift, in the center-loading coil than we do in the
base loading coil.

If we are dealing with a 5/8WL (225 deg) antenna, the phase shift
through the base coil plus the phase shift at the coil to whip
junction must add up to 45 degrees such that 225 deg + 45 deg = 270
deg = 6/8WL.
--
73, Cecil, w5dxp.com