pp.136 ELECTRICAL EXPERIMENTER June. 1919

The Rogers Underground

Aerial for Amateurs

Specially Prepared with the Collaboration of Mr.

James Harris Rogers

S INCE the publication of the original article on the Rogers Underground Wireless system published in the March, 1919, issue of the ELECTRICAL EXPERIMENTER the Editors have been literally besieged by hundreds and thousands of letters from radio experimenters in all parts of the world, asking for data on the construction of Rogers underground aerials suited to the requirements of the Wireless Amateur. The original article contained a great deal of valuable data, which should he carefully read and digested by every radio man whether he be a student or a professional. In the present article an effort has been made to answer some of the questions which have seemed to annoy the average radio "bug" considerably, - especially those residing in cities where it is difficult and frequently impossible to bury anaerial longer than a few feet. We may say right here that for those experimenters so situated, there is a solution, or in fact, two solutions, namely-to use a spiral antenna, such . has been tried out successfully in U. S Naval tests on the Rogers Systen., and which spirals may he buried in the ground a few feet, or placed in a well or other body of water and secondly, for the experimenter who is not allowed to disfigure an apartment house or other pretentious dwelling with an ugly looking aerial, there is the newly developed loop antenna, which can be used right in the radio room. Indoor aerials have been greatly perfected during the war, and now by means of greatly improved' and highly sensitive wireless receiving instruments and amplifiers available, particularly those using andions as detectors and amplifiers, .they are excellent, and satisfactory results are obtainable by means of a concentrated loop or spiral antenna, small enough to be placed in the radio laboratory.

For the present we will listen to the sound advice given by our mutual friend, Mr. James Harris Rogers, on some of the practical outstanding features of his underground system, used in conjunction with straight- away single wire underground aerials. as well as loop aerials. Among other things, Mr. Rogers has the following to say regarding the installation of simple underground aerials:

Mr. Rogers Talks to the Amateurs.

"The first installation of my underground antenna was made in the woods about a mile from my laboratory and consisted of burying wires in the earth, the wires radiated from the station as the spokes of a wheel,-some wire bare and some insulated; their lengths varied from 200 to 1000 feet(See Fig 1) It is obvious that a number of persons can receive at the same time, one operator to each wire. There is no interference, one with another. Figure One shows eight wires and a bipolar selector switch connected to the primary receiving circuit. With this switch, any individual wire may be grounded, or any two wires may be used. Bare wires give the loudest signals, but static is more pronounced. The deeper the wires are buried the better the signals, with a corresponding reduction of static. Short wires show a remarkable degree of selectivity; long ones to a less degree in proportion to their length. " (See figures Two And Three)

When using two wires at right angles to each other, signals are heard from any direction. (Figure Four). "The system works best in fresh water or very wet earth. The primary circuit should have available condenser (.001 m.f. or higher capacity) in series. When insulated wires are covered with metal, lead, iron. etc., some remarkable results are obtained. These wires may be entirely enclosed in an iron gas pipe, for instance, (Fig. 5), or the joints may be connected by rubber hose. (Fig. 6).
"Here are some measurements taken with this last form of aerial on 'Nauen' station in Germany:

Audibilities with one bulb only, on "Nauen" station, Germany :

Leingth Of Antenna	When Signals Are Weak	When Better	When Best
2,000Feet	15	25	50
2,500	30	50	100
3,000	60	100	200
3,500	120	200	400
4000	240	400	800

"Regarding the tests with loops 1 will state briefly that I have successfully tried different forms and sizes.

"I first had a well bailed out and lowered a loop antenna into it; the well was 50 feet deep. (See Fig. 7).

The signals were as loud at the bottom as when above the earth. I next had the well filled with water and

the results were the same, excepting that the note of the sending station became higher and higher as it

was lowered. Upon revolving it I found the directional characteristics were the same in the water as when out. These tests were made about two years ago, and 1 at once realized that loops or cages could be used in the dugouts of France, or on submarines when submerged. Regarding the dimensions of loop antennae used on submarines, these coils measure about 3 feet square in some instances. The wires are very heavily insulated and placed in a box filled with pitch, the connections are lead below and the coil can be revolved for directional observations."

Kind Of Wire Used for Underground Areals

Most of the inquiries from Radio Experimenters and those intending to install experimental stations. and wishing to make use of the "static-proof" Rogers underground antenna. on which signals may be received even thru a thunderstorm, indicate that the greatest problem to solve seems to be the size and the kind of wire to be used. and how it shall be buried. Some very excellent results have been obtained in experimental work carried on in one of the leading American universities with aerial conductors laid on the ground, and where the experimenter has the time or space to try this out, he may gain some useful and valuable knowledge, by experimenting in this direction. Ordinarily , the wire of whatever kind it may be, as used when installing the Rogers underground aerial, is buried about three feet deep in the earth. For most amateur requirements, the wire need to be only about one hundred to two hundred feet long, and so the digging of the ditch is not such a great problem; in fact, it can be plowed open, at least part of the depth, and where rivers, brooks, or ponds are available the insulated wire can be placed in them directly and allowed to rest on the bed.

Regarding the choice of wire to be used, it becomes evident that even bare copper or other wire may be utilized when desired, as Mr. Rogers has pointed out in the above contribution. The size of this wire should be about Number 12 or 14 B &S Guage, the heavier the better.

The official U. S. Navy reports of tests he Rogers Underground System mention that no increased efficiency is obtained using more than one wire, and that this be a No. 12 or 14 B. & S. gage, weather-proof or rubber-covered copper conductor. In any case, the free end of the wire should be well taped, and preferably covered with some rubber cement, so as to keep it insulated. Experiments have been tried both by Rogers at his Hyattsville, Md., laboratory, and also by the Navy Department, with underground aerials placed in terra cotta pipes, but this construction is rather expensive, and the results obtained do not justify its use.

Other forms of wire used both by Mr. Rogers and the Navy Department experts include lead-covered telephone cable, which is, of course, thoroughly damp-proof, while a conductor holding considerable favor with the inventor is the heavy rubber-covered, high-tension, auto ignition cable. This is highly efficient for aerial requirements, as it is stranded and therefore of low high frequency resistance.

In any case, a little common sense and logic will give the answer to many of the simple problems arising in connection with the installation of these aerials, such as, for instance, the length of aerial to be used

AUDIONS ON ALTERNATING CURRENT
Well "Radio-Bugs," the very latest thing in Audion circuits is to cut out the expensive high voltage batteries, which are forever deteriorating and necessitating the purchase of new ones, or else the use of messy miniature storage batteries, and to operate your Audions, both filament and plate circuits with ALTERNATING CURRENT. Sounds impossible, doesn't it? But it is a fact, nevertheless. Don't miss this important article, which will be worth many dollars to you, to appear in the next issue of the ELECTRICAL EXPERIMENTER. Read this special article entitled "Operate Your Audion Receiving Set on AC" by Eliott A. White, formerly instructor by Radio at the Carnegie Institute of Tech- with diagrams and complete data on the building of the transformer, and other details. This is but one of the big feature Experimental Radio Engineering articles we have in preparation for the July number. It is the greatest revelation you have ever read in radio literature. Don't miss it, "Radio Bugs"!

for a certain range of wave lengths. It is manifest that the longer the antenna, the longer the wave length to which it will properly respond. Considering that an antenna is used, having a length of say 150 to 200 feet, than practically all the shorter wavelengths of up to 600 meters and more should be readily picked up on this antenna, especially with the variable condenser hooked up in series with he primary of the loose coupler, as shown in the accompanying diagrams. Naturally the wire buried in the ground has a higher electrostatic capacity than the old style antenna wires, elevated 40 to 50 feet above the ground, and we can reduce this capacity as desired, so as to tune any certain wave lengths, by connecting another capacity in series with it: in exactly the same manner as Short wave lengths are tuned in on the regular elevated aerials. by connecting a variable capacity in series with the antenna circuit. and the primary of the loose coupler. Long wave lengths are tunable by using large condensers and loose couplers preferably.

Spiral or Loop Aerials.

As shown in the diagram, Fig. 7, interesting results were obtained with a spiral antenna, composed of a dozen or so turns of insulated wire, such as high tension cable or No. 14 R.C. solid conductor lowered into a well, both with and without water in it.

As pointed out in the original article on the Rogers underground system in the .March issue, very promising results have been obtained in transmitting with the underground antenna, and Fig. 8 shows how a small transmitting set was operated with such an aerial, coupling the exciting or spark gap circuit with the antenna oscillatory circuit by means of a two-coil oscillation transformer, L.C. In this case two metal plates, about one yard square, are placed in the earth adjacent to the well, one of which connects with the secondary, S, of the oscillation transformer, while the other plate connects with the free end of the spiral antenna.

If the spiral antenna is used, it should be mounted so as to be revolve-able on its vertical axis, and it should be placed in the vertical plane as shown in Figs. 7 and 8. Excellent results have been and should be obtained in transmitting with the under ground antenna, with the usual insulation incident to the form of conductor above
(Continued on page 187)

June. 1919 ELE

The Rogers'

Underground Aerial for

Amateurs
(Continued from page 137)

specified. where the transmitting set is one employing an audion oscillation generator',

The voltage in this case will not be extremely high, and special precautions need not be taken to provide extra heavy insulation on the buried antenna. Official tests by the U. S. Navy have shown transmission by radio over 50 miles with the Rogers underground antenna. The wire in such a case, however, should be especially well insulated to stand the higher voltage.

Regarding loop aerials in general, it would appear that we can expect a great deal from them, as some of the really remark able results achieved during the war would seem to point out. The number of turns and the amount of wire to be used in a spiral antenna, such as shown at Figs. 7 and 8 will vary of course for different wave lengths, etc., and here is where the Radio Amateur will have a chance to carry out some original experiments, which may net him some real knowledge, fame and money. Another form of antenna, so-called. and which has been tried out several years ago with such success that European stations could be copied in a laboratory located in Florida, is one composing a square form. several feet in height. This was used, .as just mentioned, to receive stations using fairly long wave lengths, say from
8,000 to 12,000 meters, W. L. Here the insulating form was wound with a layer comprising several hundred turns of insulated wire, such as ordinary annunciator wire. This antenna was successfully used in some tests made by the Marconi years ago.

- Trans-Atlantic radio reception was effected at the radio laboratory of Union College. Schenectady, N. Y., just prior to America's entrance into the World War. This aerial comprised about two dozen turns of No. 14 or 12 bare or R.C. wire, mounted on porcelain knob insulators screwed on the inside wall of the laboratory. The turns were spaced about 3 inches apart. The inside turn was 3 feet square. Flexible leads, fitted with clips, serve to connect as many turns as desired.

UNITED STATES PATENT OFFICE.

JAMES HARRIS ROGERS, HYATTSVILLE MARYLAND

RADIOSIGNALLING SYSTEM

Specification of Letters Patent. Patented Sept 9, 1919. filed January 17,1918. Serial Number: 212,198

To all whom it may concern:

First Page

Be it known that I, James Harris Rogers, a citizen of the United States, residing at Hyattsville, in the county of Prince Georges[1] and State of Maryland, have invented new and useful Improvements in Radiosignaling Systems, of which the following is a specification.

My invention relates to radio signaling systems in which radio conductors or antennas, are employed in sending and receiving signals through space by means of electromagnetic waves, and it relates more particularly to the arrangement and disposition of [15] such conductors or antennae.

My experiments have shown that coils of wire, of various shapes and sizes, act with a high degree of efficiency as radio conductors when used beneath the surface of the earth, and [20]possess the advantage of greatly reducing the static. Such coils may be buried in the earth, lowered~ into dry wells, -or submerged in water in wells or in bodies of water covering portions of the earth's surface. [25] The coils may be composed of bare wire so wound that the coils are separated from each other, such coils being used out of contact with the ground or water, and preferably insulated wire when the coil is to be[30] immersed in water or buried in the ground.

In using these coils I may and preferably do include them in a closed oscillating . circuit which is suitably associated with the [35] signaling instruments.

The invention consists of the novel construction and arrangement of apparatus and parts thereof for sending and receiving radio signals hereinafter described and [40] claimed, and illustrated in the accompanying drawings, in which drawings

Figure 1 is a diagrammatic view showing the radio conductor or coil beneath the earth's surface but insulated therefrom, [45]receiving instruments being associated with the radiating conductor;

Fig. 1a shows a conventional arrangement of sending instruments which may be substituted for the receiving instruments for transmitting signals, it being understood that either the receiving or sending instruments are employed with the arrangements shown in the following figures;

Fig. 2 a view similar to Fig.1 but show the circuit[55] of the radio conductor coil
including a portion of the ground adjacent thereto, instead of being included in a complete magnetic circuit as shown in Fig. 1;

Fig. 3 is a view similar to Fig. 1 showing the radio conductor coil buried in the earth[60] but insulated therefrom;

Fig. 4 is a view similar to Fig. 3 showing the radio conductor coil immersed in water.
Referring to the drawings, 10 indicates the signal instruments, which in Fig. 1 are those for receiving signals, while in Fig. 14 the instruments for sending signals are shown. In Fig. 1. 11 is a detector of any type, preferably an audion, 12 a telephone, and 18 and 14 the usual condensers. Any desired type 70 of instruments and arrangement of connecting circuits may be employed.

In Fig. l suitable sending instruments are conventionally shown. These comprise. a
generator 15, transformer 16, spark gap 17, [75]condenser 18 and key 19.

The above-mentioned instruments are well known in the art of radio or magnetic wave
signaling, and need not be further described.

The radio conductor or antenna is shown[80] at 20, and as illustrated consists of a coil or
spiral wound upon a suitable frame 21. The coil illustrated is flat, that is the turns lie in
the same plane, and are secured to the frame 21 in any suitable manner as by being fitted[85] in notches formed in the frame for that purpose. While this is the preferred form of coil, it will be understood that other form, may be adopted and be found to work satisfactorily. This coil is placed beneath[90] the earth's surface, as shown . Figure 1 by being lowered into a well or other depression in the earth. The coil is preferably arranged in a vertical plane. and is placed at right angles to the wave fronts of the electromagnetic[95] waves to he radiated or received. in order to obtain the maximum effect. The. well referred to is indicated at 22 and the surface of the earth at 23.

The radio conductor is connected in a[100] closed oscillating circuit indicated in Fig. 1 by conductors 24 and 25 connected to the respective ends of the radio conductor 20, and to the coil 26 of the inductive coupling the other member of which is indicated at [105]27. The closed oscillating circuit thus includes the radio conductor coil and a coil of the inductive coupling or transformer through which the receiving or the transmitting circuits and instruments are associated[110] for sending or receiving signals.

Second Page

In the modification or circuits shown in Fig. 2, one terminal of the coil is connected to ground adjacent thereto, and one side of the circuit leading from the coupling coil 26 is connected to a second ground near the[5] surface of the earth. The first mentioned ground is indicated at 28 and the second is indicated at 29. The earth connection between these two terminals 29 and 29 therefore takes the place of one side of the metallic [10] circuit shown in Fig. 1 and constitutes a portion of the closed oscillating circuit in which the coil is included.

In Fig.3, the radio conductor or coil is shown buried in the earth but insulated[15] therefrom, instead of being lowered into a well or other cavity in the earth. In this connection it will be understood that the conductor constituting the coil as well as the circuit conductors 24 and 25 are insulated[20] so that the wires themselves do not come in electrical contact with the ground.

In the arrangement shown in Fig. 4 the coil is shown immersed in water, this may be considered as a portion of the earth's surface. [25] Here also insulated conductors are employed.
Throughout receiving signals I have found that in receiving signals the strength and clearness of the signals seems[30] to improve as the depth below the surface of the earth is increased, and the static is greatly reduced by the employment of the coil below the surface of the earth. Tests; which I have made with the coil immersed [35]to a depth of fifty feet in water have given excellent results.

In the practice of my invention I do not wish to be limited to the particular arrangements shown in the drawings or[40] described above, but contemplate all such changes as are within the scope of the invention. The invention is applicable to: trench warfare for communicating between different portions or between[45] different trenches. It is also applicable to various types of land stations, and may be also used with advantage on portions of the earth where there there is water, such as on ships at sea where the radio conductor may be[50] mounted upon the ship in any suitable way or may be lowered overboard from a vessel. It will be understood also that. it not necessary that the sending and receiving instruments should be above ground as [55]illustrated , and these may be under the surface of the ground in suitable chambers, bomb-proof trenches, or in caves, et cetra. As such applications of the invention are obvious, it is thought unnecessary to illustrate them.

In the practice of the invention [60]that static is greatly reduced and the directional effects obtained are excellent.

From the above it will be apparent that a radio conductor of great length may be employed
beneath the surface of the earth[65] without necessitating a corresponding amount of trench work or other labor for placing the conductor beneath the surface. It will also be understood that the conductor may be made of any desired length according to[70] conditions or requirements.

The term "radio conductor" has been employed throughout the specification and claims synonymously with the term "antenna" to indicate the conductor from which [75] the oscillations are radiated in sending messages and are received when receiving messages.

What 1 claim as new and desire to secure' by Letters Patent of the United States is:[80]

1. A radio signaling system comprising a
coiled radio conductor beneath the surface of
the earth and connected in a closed oscillating
circuit
2. A radio signaling system comprising a [85]
coiled radio conductor buried beneath the
surface of the earth but insulated therefrom and
connected in a closed oscillating circuit.

3. A radio signaling system comprising a coiled
radio conductor immersed in water[90] but insulated therefrom and connected in a closed
oscillating circuit.

4. A radio signaling system comprising a coiled
radio conductor beneath the surface of the earth
but insulated therefrom[95] and connected in a
closed oscillating circuit, and electromagnetic
wave signal instruments inductively associated
with said oscillating circuit.

5. A radio signaling system comprising a [100]
radio conductor connected in a closed oscil-
lating circuit and in the form of a flat coil
or spiral beneath the surface of the earth
but insulated therefrom and positioned at
right angles to the wave fronts of the waves [105]
sent or received, and electromagnetic wave
L signal instruments associated with said conductor.
In testimony whereof I have hereunto set my hand.
JAMES HARRIS ROGERS.