US1893287A

US1893287A - Airplane radio equipment

Info

Publication number: US1893287A
Application number: US387894A
Authority: US
Inventors: Jenkins Charles Francis
Original assignee: FRANCIS JENKINS Inc C
Current assignee: C FRANCIS JENKINS Inc; FRANCIS JENKINS Inc C
Priority date: 1929-08-23
Filing date: 1929-08-23
Publication date: 1933-01-03
Anticipated expiration: 1950-01-03

Description

Jam. 3, 1933. c. F. JENKINS 1,393,287

AIRPLANE RADIO EQUIPMENT Filed Aug. 23, 1929 Patented Jan. 3, 1933 UNITED STATES TENT OFFICE CHARLES FRANCIS JENKINs oF WASHINGTON, nrs'rmcr or CiOLfiMBIA. ASSIGNOR T 0. FRANCIS JENKINS,.INC., or WASHINGTON, nis'rnIer OF COLUMBIA ninrnnnnwnnmo nomfmnnr I Application filed August 23,1929. Serial 'No. 387,894.

This invention relates to radio equipment carried aboard an airplane, andhas 'forits principalobject a simple assembly of-parts which wholly avoids interference from the electrical equipment of the engine. Heretofore it has been customary in airplane-radio equipment (a) to suspend a wire under the plane with a lead weight, a lead fish attached to the free end there'ofto hold it steady, and as nearly vertical as possible; or (b) to fasten the antenna to .a vertical mast carried by the plane. (0)1Antennae have also occasionally been fastened along wing tip to tail structure. I

All such antenna locations have serious interference from engine ignition system radiation. For this reason costly shielding of the magnetos, the spark'plugs and hightension leads must be employed to avoid ignition noises in the exposed antenna preventing voice receptionaboard the plane, and seriouslyinterfering with code reception.

the leading edge of the wings, and-(d) from Electrical high-tension radiation fromthe engine ignition system is spherically radiated; and envelops the plane, but by exploration it has been discovered that there exists a radiation-free zone aft of the plane. This probably results from absorption by the metal parts of the plane fusilage, creating an electrical shadow, and an interference-free zone behind the plane.

Whether this theory is correct or not, it has been found that there is an interference free zone aft in the line of flight; and that if the antenna is held axially in this zone, no interference to radiosignal reception results.

In putting this discovery into useful service a shielded radio set is mounted in the plane, in any convenient place. The ground Wire is fastened to the metal work of the plane, acting as acoimterpoise. The antenna lead-in end is run through a shield, the unshielded end of the antennaflying aft from the tail structure. The free end of the antenna or antenna wire has a very light weight drag attached thereto to keep it taut. V

- This drag may be for example, a small celluloid ball, although preferably a body of stream-line forinp A balsam-wood fish serves.-quite satisfactorily. ,A rash with screw pitched fins thereon also assists in preventing it' floppin-gin the :slip stream by. cause ing the fishto rotate rapidly inthe extended axis of {the wire. Of course a-swivel is employed betweenthe Wire and the fish.

In the drawing herewith illustrating the invention, A is;;an airplan e, in which isra radio'set B. withan antenna G, attached thereto. On the free end 'of the antenna a light weight drag E is fastened. The lead-in end of the antenna is shielded in a tube D.

The operation of the invention is so obviousto those skilled in the airplane-radio art as-to need scarcely more than-a brief description. I

:Whether the'an-tenna isthrown overboard after the plane in flight, aswas d'one in ap'plican-ts firstexperiments, or is unreeled from a spool until the. right length of antenna isfiying, is immaterial; 'in either event the drag holds the wire taut in the electric shadow in .the "Wake of the plane, which is the object sought, namely, that the antenna doesnot pick up any radiationfrom-the ignition system ofthe en-ginej 1 Incidentallythe antenna with a light Weight dragholdingit axially in the slipstream creates far less parasitic resistance than eithera depending antenna or a mast supported antenna; a

:Alsothis location of the antenna permits the use of such a length of Wire as Willtune to theprimary of the broadcast frequency, which issa more efiicientmethod than the employinent of a short antenna tuned to a harmonic frequency.

Quite obviously it is easier, and far less expensive to shiel-dthe radio set than it is to shield the engineignition system; which latter also gives unending trouble in engine servicing and repair. 7

lVhat I claim, is 1 1.. The combinationiWith an airplane hav ing a: metallic structure including an engine and consequent engine systemzradiatiomby reason of which metallic .structure'an interference free. zone is created, of a radio set mounted on the .airplane'inthe rearofthe Li L) engine, and an antenna connected tothe radio set and projecting from the airplane through the tail thereof to fly in substantially a horizontal plane and axially of the plane behind the airplane and its engine within the interference free zonewhereby there is prevented interference from engine ignition radiation without shielding the magnetos, spark plugs and high tension leads. I

2. The combination; with an'airplanehaving a metallic structure including an engine and consequent engine system radiation, by reason of which metallic structure there is created an interference free zone extending behind the airplane, of a shielded radio set mounted within the airplane in the rear of the engine, an antenna connected to the'radio set and projecting from the airplane through the tail thereof to fly in substantially a horizontal plane and substantially axially of the airplane and behind the airplane and its en gine in the interference free zone whereby there is avoided interference from engine ignition radiation, and means carried at the outer end of theantenna "to maintain the same taut in said radiation-free zone'aft-of the airplane.

3. The combination with an airplane having a metallic structure including an engine and consequent engine system radiation, of

a shielded radio set mounted within the airplane in the rear of the engine, a tube in the airplane leading rearwardly from the shielded radio set to and through the tail of the airplane, and an antenna connected to the radio set and passing through said tube and shielded thereby within the airplane and having its outer portion projecting therefrom to 'fly unshielded in substantially a horizontal plane and substantially axially of the airplane'behind the latter and its engine and within aninterference free zone created by parts of the metallic structure whereby there is avoided interference from engine ignition radiation.

4. The combination with an airplane having a metallic structure including an engine and a consequent engine system radiation, of a radio set mounted within the airplane in the rear of the engine, and an antenna connected to the radio set and projecting from the airplane so as to fly in substantially a horizontal plane behind the engine and wlthin an interference free zone created by the metallic structure whereby there is avoided interference from engine ignition radiation without shielding the magnetos, spark plugs and high tension leads. V

5. The combination with an airplane having a'metallic structure including an engine and consequent engine system radiation, of a radio set mounted on the airplane. in the rear of the engine, an antenna extending from the radio set to and beyond the tail of the airplane and unconnected with the tail, the portion of the antenna beyond the tail being the only portion thereof exposed outside the airplane and being maintained taut in a substantially horizontal plane substantially axially of the airplane behind the tail of the airplane incident to forward movement of the airplane in fiightand being located within an interference free zone created because of electrical shadows cast by the metallic structure and thereby rendered free of interfering disturbances incident to engine system radiation. I

6. The combination with an airplane having a-metallic structure including an engine and a consequent engine system radiation, part of said metallic structure creating an electrical shadow and aresulting interference free zone, of a radioset mounted within the airplane in the rear of the engine, an antenna located behind the engine and wholly within said zone and connected to the radio set and having its outer end. projecting from the rear of the airplane to flyin substantially a horizontal plane and substantially axially of the airplane and its engine whereby there is avoided interference from the engine ignition system, andmeans carried at the outerend of the antenna to maintain the same taut in said substantially horizontal plane.

7 The combination with an airplane having a metallic structure including an engine and a consequent engine system radiation, ofa radio set mounted within the airplane inthe rear of the engine, and an antenna connected to the radio set and having its outer end projecting from the rearof the airplane tofly in substantially a horizontal plane and substantially axially of the airplane and its engine to prevent interference from the engine ignition system. 7 Y

8. The combination with an airplanehaving a metallic structure including an engine and a consequent engine system radiation, of

a radio set mounted within the airplane in the rear of metallic structure that creates an electrical shadow in the rear of the, engine, an antenna connected to the radio set and having its outer end projecting from theairplane only at the rear thereof to fly onlyin the rear of the airplane and in a substantially horizontal plane during the flight of the airplane so as to confine the dispositionof the trailin an'- tenna in the radiation-free zoneaftcof the airplane and created by 'said electrical shadow. r r

9. The combination with an airplane having a metallic structure including an engine and a consequent engine system radiation, which metallic structure castsfan electrical shadow aft that part of the engine system that produces said engine system radiation, of a radio set mountedwithin the airplane in the rear of the engine, and an antenna which is located wholly within said electrical shadow, which isoonnected; to the radio set,

and which has its outer end always disposed in substantially a horizontal plane during the normal forward flight of the airplane whereby the antenna during the normal forward flight remains in the radiation-free zone created by said electrical shadow.

10. In radio equipment aboard a tractor engine airplane having an interference free zone aft the engine, an antenna located aft the engine and wholly within the interference free zone and approximately parallel to the axis of the fuselage of the plane.

In testimony whereof I have afiixed my signature.

CHARLES FRANCIS JENKINS.