US2112547A - Antenna counterpoise system - Google Patents

Description

March 29, 1938. K. VOGT ANTENNA COUNTERPOISE SYSTEM Filed Oct. 10. 1936 INVENTOR KARL VOGT ATTORNEY Patented Mar. 29, 1938 UNITED STATS e since ANTENNA COUNTERPOISE SYSTEM Germany Application October 10, 1936, Serial No. 104,920 In Germany November 12, 1935 2 Claims.

It is known to substitute a counterpoise arrangement for the ground for the elimination of losses occurring in grounding arrangements. Counterpoises are constructed in such manner that radially running insulated wires are stretched over the ground at a height of about .5 to 5 meters. The length of the counterpoise wires is mostly small compared to the wavelength for antenna systems for medium and long waves. In antenna systems for short waves the wire length is chosen about equal to the height of the mast, the maximum length used being about one-quarter wavelength,

If we have a fixed antenna and a counterpoise and wish to make a quick change of the Wavelength, then we must choose the counterpoise length as long as possible for good eificiency and at the same time so that optimum coupling reactance is substantially the same for all wavelengths. If there is a fixed antenna and counterpoise, and if it is desired that there be a quick change of wavelength, one must choose that counterpoise length which is as long as possible for good efiiciency, and at the same time such that the optimum coupling reactance is substantially the same for all wavelengths. Since the counterpoise wires are insulated, the current flowing therein will have a spatial distribution similar to the distribution in horizontal antennas over the ground. The current distribution and natural oscillation depend in this type on its capacity with respect to earth. If the distance to earth is small, the natural oscillation of a horizont'al conductor is about equal the double wire length plus 10%. In distances, however, that are larger than (one-half wavelength), the natural oscillation of the horizontal conductor is greater than the double wire length by only about 5%.

Now, if the operating Wavelength in an antenna system is about equal the double length of the counterpoise wires, high resistances exist at the base point of antenna, For somewhat longer waves the resistance decreases to the size of the radiation resistance of antenna and decreases still further with longer waves.

In View of the above, and in accordance with the invention, the counterpoise wires are chosen smaller than half the wavelength of the shortest operating wave for the purpose of coupling an antenna system with insulated counterpose to a transmitter within a wider wave range, wherepoise wires.

by the coupling resistances are to vary very little. The optimum value for insuring the most favorable antenna efiiciency over the entire wave range is calculated from the disclosed values for the natural oscillations of a horizontal conductor at different heights. For small distances above ground the maximum length of the counterpoise wires amounts to about Ax, for greater heights about .45)\ of the shortest operating wave.

The single figure of the drawing shows an embodiment by way of example. The two masts M sup-port antenna A insulated with insulators J. Lead line Z is connected through coupling coil S with counterpoise wires G likewise insulated (insulators J). The length of the counterpoise wires shall, in accordance with the invention, be somewhat smaller than half of the shortest operating wavelength.

The excitation of horizontal conductors to harmonic oscillations, as is well known in prior art, may also apply to counterpoise wires having a longer length than indicated above, resulting in a current distribution corresponding to that of a horizontal antenna excited to harmonic oscillations. It will suit the purpose best to choose in this case the length of the counterpoise wires as an integral multiple of the value indicated for the shortest operating wave. The wave range towards the longer waves is, however, limited in this case since the current distribution in the wires with increasing wavelength is formed in the manner that a current nodal point is located at the base of antenna. Thus the resistance varies at this point from a few ohms to several thousand ohms. Considerable difliculties would accompany the coupling of transmitter in this case. If the length of the counterpoise wires is chosen equal to A, that is, equal to double half of the wavelength, the longest wave coupled with small resistance to transmitter is somewhat larger than the double length of the counter- If, on the other hand, the length of the counterpoise wires is chosen as a higher multiple of M2, the useful wave range tends to become smaller and smaller.

What is claimed is:

1. In combination, an antenna circuit comprising an antenna and an open-ended counterpoise wire insulated from ground, said circuit being arranged to operate over a wide band of frequencies, a source of oscillations adapted to function over a wide range of frequencies, a fixed inductive coupling device between said antenna circuit and source, the length of said counterpoise wire, as measured from its open end to the base of said antenna, being less, but not much less than onehalf the minimum wavelength of said range, whereby the effective antenna circuit resistance, including counterpoise, antenna, and connecting portion, decreases as the operating frequency decreases so as to compensate at least partially for the decreasing mutual impedance of said fixed coupling.

2. 'In combination, an antenna circuit comprising an antenna and'an open-ended counterpoise Wire insulated from ground, said circuit being arranged to operate over a wide band of frequencies,

a source of oscillations adapted to function over a wide range of frequencies, a fixed inductive coupling device between said antenna circuit and source, the length of said counterpoise wire, as measured from its open end to the base of said antenna being approximately equal to .4 of the minimum wavelength of said range, whereby the effective antenna circuit resistance, including counterpoise, antenna, and connecting portion, decreases as the operating frequency decreases.

KARL VOGT.

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