(2) Chang-Hong Liang and David K. Cheng, IEEE Trans. Antennas and
Propagation, v 31 n 3, May 1983
Insulated Antennas
Captions
Fig. 1
Cross section of an insulated antenna. Rw- radius of wire, Rd-
radius of dielectric, K- dielectric constant of insulation. The
diameter ratio may be used.
Fig.2
Very approximate effect of insulation with dielectric constant of 3 on a spherical antenna, showing reduction of resonant frequency as insulation thickness increases. The limit of reduction is 1 over the square root of the dielectric constant.
Fig. 3
Resonance length factor of dipoles and monopoles as a function of its length to diameter ratio. For quarter-wave verticals over an infinite ground, use the dipole curve with twice the monopole length to diameter ratio. "Half-wave" dipoles are always shorter than the free-space one-half wavelength at resonance.
Fig. 4
Resonance length factor of a square quad loop as a function of its circumference to radius ratio. Use for equilateral delta loops with negligible error. "One-wavelength" bare conductor loop perimeters are always longer than the free-space wavelength at resonance.
Fig. 5
Insulated antenna "P-factor" as a function of the insulation to wire diameters (or radii). Interpolate between curves for the exact dielectric constant. Use equation 6 for values outside the curves.
Fig. 6
Approximate shortening effect of insulation on dipoles. Select the uninsulated length factor curve using data from Fig. 3, and for the P-factor from Fig. 5, interpolating as necessary. For monopoles use one half this indicated length. See text for values beyond the data shown.
Fig. 7
As Fig. 6, but for loops. Enter with data from Figs. 4 and 5. Insulated loops may have a perimeter less than one wavelength at resonance.
hR.P.Haviland,1035 Green Acres C N, Daytona Beach FL 321119
cInsulated Antennas
REFERENCES
(1) Topical Bibliography on Antennas, The ARRL Antenna Book, 15th ed., ARRL, Newington, CT. 1988
(2) From Beverages thru Oscar - A Bibliography 1908-1988, Didah Publishing, Nashua, NH. Available on disk or microfiche.
(3) F. E. Terman, Radio Engineer's Handbook, McGraw-Hill, NY, 1943
(4) J. H. Richmond, Radiation and Scattering by Thin-wire Structures in the Complex Frequency Domain, NASA Report CR-2396, May 1974. Available from NTSC and from depository libraries.
(5) J. H. Richmond, Computer Program for Thin-wire Structures in a Homogenous Conducting Medium, NASA Report CR-2399, June, 1974. Availability as (4)
(6) National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161
(7) The ARRL Antenna Book, Current ed., ARRL, Newington, CT.
(8) R.. P. Haviland, The Quad Antenna, CQ Books, Hicksville, NY, Summer, 1992
(9) J. H. Richmond and E. H. Newman, Dielectric Coated Antennas, Radio Science, v11, n1, pp. 13-20, National Bureau of Standards
(10) David Lammersdorf, An Experimental Investigation of Dielectric Coated Antennas, IEEE Trans. Ant. Prop., AP-15, N.6, Nov. 1967, pp 767-771