US1301246A - Receiver for wireless signals. - Google Patents

Description

C S FRANKLIN RECEIVER EpR WIRELESS SIGNALS.

- APPLICATION FILED FEB. 26, 19I9- 1,301,246..

Patented'Apr. 22, 1919.

Invavzaor duce oscillations lations 20 d 7 when workin RANKLIN, OF LOIIIDON, ENGLAND, ASSIGNOR T0 a WIRELESS TELEGRAPH COMPANY OF AMERICA, OF NEW YORK, N.

romrron or new mnsmr.

momvanron. Wmmnss SIGNALS. ,24g Specification of Letters Patent. Patented Apr. 252, 1919.

Application med February 28, 1919. Serial No. 279,896.

To all whom it may concern:

Be it known that I, CHARLES SAMUEL FRANKLIN, a subject of the King of Great Britain, residing at Marconi House, Strand ndon, England, have invented new and useful Improvements in Receivers for Wireless Signals, of which the following. is a specification.

In receivers based on the interference rinciple it is usual to em loy a local oscilfittOl which can be so ad usted as to prodilfering in frequency by a desired amount from the duced in the receiver by the incoming waves. In some well known receiver's the receiving device is its own local oscillator.

The result is that during reception there are in the receiving circuits two sets of modwhich interact with each other, proucing a compound oscillation of varying amplitude.

The receiver usually rectifies this compound oscillation into a uni-directional current of varying strength and so produces in the receiving telephone a note which has a frequency equal to the difference of the frequencies of the received and local oscillations, and which can therefore be, adjusted by varying the frequency of the local oscila ions.

The constancy the constancy of ceived and local oscillations. For frequencies below about 1,000,000 per second (300 meter waves) it is not difiicult to maintain a sufficiently constant frequency; for frequencies about 3,000,000 it is still practicable though not easy to maintain a sufliciently constant frequency; for frequencies about 30,000,000 it is practicall impossible to maintain the frequency su ciently constant.

Assuming 30,000,000 to be the frequency received, then -the local oscillator must give a frequency of 30,001,000 or 29,999,000, in order to give an interference note of 1,000. Should either frequency of one per cent. the interference note may change; from 1,000 to 4,000. Practically with frequencies of this order the inte erence note varies so rapidly and to such an extent with the small variations of frequency which, take place that the signals are dable.

of the note dependsupon oscillations pro audible limits. Th

the frequency of the revary one hundredth According to this invention, the frequency of the local oscillatlons is varied by a small percentage, regularly and in by arranging partly of segments arranged on a rotating disk or cylinder, so that the capaclty varies continually between two limits. receiver constructed according to this invention works as follows Assume the received frequency to be 30,- 000,000 and the local generator arranged to give 30,000,000 frequency with variations of a half per cent. above and below this 1,000 times per second. During reception an interference note is produced which varies from zero to a frequency of 150,000. An audible sound is produced in the telephone only during the time that the interference note is varying through the range from about 8,000 to zero and back to 8,000; that is to say, while the interference note is within e period occupied by this range is so short that only a click occurs in the telephone for every variation between the above limits of the frequency of the local oscillator. As, however, this variationoccurs 1,000 times per second, a clear note havin a frequency of 1,000 per second is heard w enever signals are received.

receiver for short waves is thus. ob-- tained which has the great sensitiveness of the interference receiver, but is independent of very smallvariations in frequency either 1in the received waves or in the local oscilator.

The invention is illustrated by the accompos1tio1 1of one of the segments 6 relative to the strips (1 a and varies mum and minimum as the the strips.

. Across the coil L is connected a thermionic device at in series with a battery B so arranged as to produce high frequency oscilbetween a maxi segments 6 pass lations in the circuit L C a a in a manner now well understood.

What I claim is 1. In an interference receiving apparatus for wireless signals, a circuit containing a generator of local oscillations, and means whereby the frequency of said local oscillations is caused to vary regularly and in a continuous manner.

2. In an interference receiving apparatus for wireless signals, an antenna, a circuit associated therewith containing a generator of local oscillations, and means for regularly and in a continuous manner increasmg the frequency of the local oscillations above and decreasing them below the frequency of the received oscillations.

3. In a wireless telegraph receiver, the combination of an aerial, an oscillatory circuit coupled thereto, local means for generating in said circuit high frequency oscillations, and means for varying regularly and continuously the time period of said circuit.

4. In a wireless tele aph receiver, the combination of an aeria an oscillatory circuit coupled thereto, local means for generating oscillations in said circuit, and means for varying regularly and continuously the frequency of such oscillations.

5. In a wireless telegraph receiver, the combination of an aerial, an oscillatory circuit coupled thereto, local means for generating in said circuit high frequency oscillations, and means for varying regularly and continuously the'capacity of said circuit.

6. In an interference receiving apparatus for wireless signals, an antenna, a local circuit associated therewith containing a generator of oscillations, and-means for re larly and continuously vvarying the equency of the local oscillations above and below the limiting frequencies at which the beats produced by reaction of the received and local oscillations are audible, said means being so constructed that the frequency of said beats passes through the audible range so frequently as to produce a distinct note in the receiver corresponding tothe group frequency of the audible beats.

CHARLES SAMUEL FRANKLIN.

Witnesses:

Gnoncn J TRUSTY, LEON DE SOUTH.

Images