US2342736A - Radio cable - Google Patents

Description

Feb. 29, 1944. R HERZOG mL 2,342,736

RADIO CABLE Filed June 12, 1941 fi, #5MP-coso Z @QA/aac' roe 4 I i cofvoacroe Patented Feb. 29, 1944 RADIO CABLE Robert Herzog, Alfred Wiessner, and Rudolf Hintze, Berlin, and Fritz Gutmann, Schonciche, near Berlin, Germany; vested in the Alien Property Custodian Application June 12, 1941, Serial No. 397,704 In Germany October 1, 1940 Z Claims.

The present invention has for its object to create a wide-band radio cable of constantattenuation, that is, a cable suitable for distortionless transmission'as regards frequencies up to a certain value.

According to the invention the internal conductor, formed as a tubular conductor, and the outer conductor of the cable consist of radio strands so constructed that the limiting frequency is a multiple of the highest Working frequency. Preferably, the insulating compound of the cable is plastic and has a leakance constant less than 10-3.

These and other features of the invention will be understood from the following description and the accompanying drawing. which is a diagrammatic fragmentary elevation of a form of cables as provided by the invention.

The tubular internal conductor 2 consists of interlaced radio strand and is seated on a hempcord I. 3 denotes a plastic insulating compound of low losses, in which the conductor 2 is embedded in a manner to avoid any air cavities between the two. The outer conductor 4 likewise consists of interlaced radio strand and is mounted .on the insulating compound 3. In the case shown by way of example the conductor 4 is surrounded With an insulating sheath 5 that may be of the same materiales the compound 3 by which the conductors 2, 4 are insulated from each other. A protective sheath 6 for the insulating sheath 5 may be made of any suitable artificial material.

As will be seen in the drawing, the strands forming the conductors 2, 4 are each arranged as rightand left-hand lays in order that the magnetic field outside conductor 4 be substantially neutralized.

Preferably, in order to provide for a good utilization of the cable and an economical manufacture thereof, the conductors 2, 4 may be made of wires different in thickness but so calculated that both conductors 2, 4 are given the same hunting frequency. The eddy current factor may be assumed approximately to be where w=wo is the limiting frequency for the cable. In the case of the novel cable ZOIS 10% which means that o may acquirevalues up to the cable and the weight thereof may be made to be very small. For instance, the weight of 1000 metersof a cable whose outer diameter is about 2'7 millimeters is about r100 kilograms. The small cross-sectional area of the cable is also due to` the fact that there is no air space insulation. In this regard therefore the invention entails a considerable saving in material. Equally, any lead sheath may be dispensed with. The sheath B of artificial material, which for instance may be' composed of interlaced tapes, allows the cableto be buried in the same manneras a cable equipped with lead sheath and armouring.

Attenuation tests regarding a cable of this kind and relating ,to a frequency range of from 60 to 1300 kilocycles per second have given the following results: with 300 kHz., that is, 300 kilocycles per second, an. attenuation, independent of frequency, of about 72 mN./km., that is, '72 millinepers per kilometer, was obtained. From 300 kHz. onward the attenuation rises. For instance. with about 600 kHz. it amounts to mN./km., with 1000 kHz. to 126 mN./km., and with 1300 kHz. to mN./km, It will thus be seen that with 300 kHz. the attenuation solely depends on the ohmic resistance of the conductors 2, 4 ,and that even in the case of higher frequencies the leakance loss'does not appreciably affect the total attenuation. For example, with 200 kHz. the leakance loss is 1.6%, while with 400 kHz. it is .3.7% and with 1000 kHz. it amounts to 8.5% of the total attenuation.

What is claimed is: l. A concentric cable for transmitting a working frequency range comprising a tubular inner conductor and an outer conductor concentrically around the inner conductor, said conductors both being made of conducting strands interleaved in right and left hand lays, the strands of the outer conductor being of greater thickness than those of the inner conductor, and each of said conductors having the same limiting frequency, said limiting frequency being a multiple of the highest working frequency.

2. A wide-band radio cable of constant attenuation comprising concentrically spaced tubular inner and outer conductors insulated from each other, the two conductors being formed of wire strands interleaved in right and left hand lays, the strands of the outer conductor being of greater thickness than those of the inner conductor, the limiting frequency being of equal value for both conductors, and said limiting frequency being so related to the highest working frequency of the band as to be a multiple thereof at any point within the working frequency range.

ROBERT HERZOG. ALFRED WIESSNER. RUDOIF HINTZE. mitm GUTZMANN.

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