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Патент USA US2131109

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Sept. 27, 1938.
P. D. LOWELL
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RADIO TELEGRAPH RECEIVING SYSTEM
Filed July 25, 1953
'
2,131,109
I
Patented Sept. 27, 1938
I “ 2,131,109‘
UNITED STATES
PATENT ToFFica
2,131,109
RADIO TELEGRAPH RECEIVING SYSTEM '
Percival D. Lowell, Chevy Chase, Md., assignor to
Radio Corporation of America, New York,
N. Y., a corporation of Delaware
>
Application July 25, 1933, Serial No. 682,132
9 Claims. (01. 250—8)
My invention relates broadly to radio receiving fer, through the intermediate frequency‘ampli?er
apparatus and more particularly to apparatus for
the reception of continuous wave radio telegraph
code signals.
01
One of the objects of my invention is to provide
a circuit arrangement for a continuous wave
and second detector to the audio frequency am
pli?cation system, of that frequency ‘to which the
audio frequency ampli?cation system is selective
ly adjusted.
I
_
‘
-
"
I
‘ Other and further objects of my invention re
radio telegraph receiving system having means
for stabilizing the tone frequency of the received
side in the selective continuous wave. radio tele
graph signal receiving system as set forth more
signals.
fully in the speci?cation hereinafter‘following by
,
Another object of my invention is to provide reference .to the accompanying drawing which 10
an improved superheterodyne type of radio receiv - diagrammatically "illustrates the system of my in-__V
ing circuit for the reception of continuous‘wave Vention. V '
telegraph ‘signals having means for stabilizing .,In. thelcircuits now commonly used in radio >
the tone frequency of the reproduced telegraphic telegraphy it is. customary to employ either an
signals.
oscillating detector or a separate oscillator for the 15
Still another object of my invention is to pro ,purpose. of generatingoscillati'ons to‘ beat with
vide a circuit arrangement for superheterodyne ‘the incoming signal waves, thereby rendering the:
type of radio receiving systems wherein the high > incoming code signals audible to, the ear or useful
frequency oscillator which coacts with the ?rst in operating a‘recorder'or printer; It is the pur
detector is continuously modulated at a constant
frequency adapted to be selectively impressed
upon the audio frequency signal output circuit in
accordance with the received telegraphic signals.
Still another object of my invention is to pro
vide a continuous wave superheterodyne type of
pose of my invention to provide a more stable, ‘’
simpler ‘and-more easily. adjusted method ' of
rendering‘ the vcontinuous wave signals audible
than that obtainable in'the usual beat frequency.‘ '
oscillatortype of circuit. My invention of neces
sity requires a receiver'o'f the‘ superheterodyne
type in which an oscillator is employed to convert.
frequency oscillator arranged to coact with a ?rst 'the incoming signal frequency to a frequency of
detector in combination with a source of audio a different value. I havefound that if the oscil
frequency modulating energy which is adapted to lator inasuperheterodyne receiving system be
30 be transferred through the intermediate frequen
continuously modulated at. aconstantaudio fre
cy ampli?er, second detector and audio frequency quency, this audio frequency will not pass through
ampli?er of the superheterodyne receiver in ac
the intermediate frequency ampli?er, second de
cordance with the telegraphic signals which are tector and 'audiofrequency ampli?er unless a con
received for thereby determining the character of tinuous. wave incoming signal isalso present. In
the audio frequency signaling energy which is de- ‘ otherwords, an incoming continuous wave signal 35
livered to the audio frequency signal‘ output cir
When'it reaches the oscillator, besides being con
verted to a different frequency, also becomes mod-v
radio telegraph receiving system including a high
cuit.
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'
.
7 A further object of my invention is to vprovide a
circuit arrangement for the selective reception of >
radio telegraph signals through a superheterodyne
receiving circuit with minimum interference from
static or undesired signals in which a source of
audio frequency signaling energy at the receiver
is rendered e?ective upon a preselector circuit of
~ an audio frequency ampli?cation system which
tends to reject undesired frequencies and static
disturbances.
.
A still further object of my invention is to pro
vide a selective continuous wave radio telegraph
ulated, at'the audio‘ frequency. Thelconverted
andmodulated signal will then pass through the
intermediate frequency ampli?er, second detector
andaudio frequency ampli?er and the dots and
dashes will be reproduced at thefrequency of the
audio modulation. The system of my invention is
rendered‘ especially selective by reason ‘of the.
peaked characteristic of the audio frequency am
pli?er at a certain frequency. I may also employ
an audio frequency ampli?er having a sharp band '
pass- characteristic for the‘ purpose of eliminating’
receiver of the superheterodyne type wherein the interference or reducing the response of the re-,
high frequency oscillator which coacts with the‘ ceiver to static ‘disturbances. The audio frequen¢
?rst detector is modulated at a predetermined . cy response characteristic of the audio frequency '
audio frequency rate to which the audio frequency ampli?er system is selectedto correspond to the
ampli?cation system is selectively tuned whereby modulation’ and frequency ofth-e highfrequency
' the incomingtelegraphic signals effect the trans
oscillator, ‘thereby rejecting ~undesired signalv fre¢ i
2
2,131,109
quencies and reducing the response to static dis
turbances.
'
Referring to the drawing, I have shown a
superheterodyne receiver circuit comprising the
antenna circuit l, the radio‘ frequency ampli?er
2, the ?rst detector 3, the oscillator 4, the inter
mediate frequency ampli?er 5, second detector
6, audio frequency ampli?er "I, and audio fre
operation. I have used the circuit in the opera
tion of automatic printers by radio with highly
successful results over substantial distances.
While I have described my invention in one of
its preferred embodiments, I desire that it be Q1
understood that modi?cations may be made and
that no limitations upon my invention are in
tended other than are imposed by the scope of
'
quency output circuit 8 which connects to a signal the appended claims.
indicating device, recorder or printing mecha
What I claim as new and desire to secure by
nism. The oscillator 4 is modulated by the , Letters Patent of the United States is as follows:
1. A continuous wave radio telegraph receiving
source of audio voltage I 0 which is introduced
into the oscillator circuit through the coupling system comprising a superheterodyne receiving
transformer 9. The coupling transformer 9 in
circuit including a ?rst detector, a high frequency
cludes a primary winding H connected with the oscillator connected therewith,v an intermediate
source of audio voltage I 0 and a secondary wind
frequency ampli?er connected with said ?rst de
ing l2 connected in series with the input circuit tector, a second‘ detector connected with said
of the oscillator between the biasing resistor l4 intermediate frequency ampli?er, a preselector
and the lower terminal of the tuned circuit 15. circuit connected with the output of said second
detector, an audio frequency ampli?er system
20 The oscillator includes the coupling coil IS in the
output circuit thereof inductively related to the connected with said preselector circuit and a
inductance of the tuned circuit [5 in the input source of audio frequency oscillation connected
circuit of the oscillator. The high frequency with said high frequency oscillator, said prese
oscillations generated by oscillator 4- are im
lector circuit being tuned to select the frequency
pressed upon the circuit of the ?rst detector 3 of said source of audio frequency oscillation.
by the electro-magnetic coupling between oscil
. 2. A continuous wave radio telegraph receiving
lator coils l5, l6 and the tuned grid circuit of the system comprising a superheterodyne receiving
detector 3. The source. of potential [8 supplies circuit including-a ?rst detector, a high frequency
plate excitation for all of the electron tubes. I oscillator connected therewith, an intermediate
30 have illustrated the indirectly heated type of frequency ampli?er connected with said ?rst de
electron’ tube employed in the, oscillator and
throughout the several stages of the receiver.
The audio‘ frequency ampli?cationsystem which
has been represented for purposes of explainingv
my invention, has a single ampli?er stage, pre
ceded by a preselector circuit which I have desig
nated at I9. The preselector circuit includes
the secondary Winding audio frequency trans
former 20 with a condenser 2| connected in shunt
I thereto and adjusted. to the audio frequency pro
duced by the source of audio voltage Ill. Inas
muchas the tuned circuit 19 is selectively respon
sive to the frequency of the modulator Hl, inter
fering. frequencies and static effects produce a
minimum effect upon audio frequency ampli?ca
tion system. 1. The tuned circuit I9 is matched
to the frequency of the modulator Ill. The fre
quency of the modulator ID will not pass through
the intermediate ampli?er 5 or the second de
tector E to the transformer 20 and preselector
circuit I9 unless a continuous wave incoming sig
or printing mechanism which may be connected
to the audio frequency output circuit 8.
The condenser 22 connects across the second
ary winding 12 and across the biasing resistor l4
and provides a radio frequency path for the os
cillations generated by oscillator 47 around‘ the
frequency oscillation connected'with' said high
frequency oscillator for‘ continuously modulating
the oscillations impressed on said ?rst detector
at an audio rate,’ the frequency adjustment of
said preselector circuit being matched to corre
spond to the frequency of said source of audio
frequency oscillations.
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.
3. A- continuous wave radio telegraph receiv 45
ing systemv comprising a superheterodyne‘ re
ceiving circuit including a ?rst detector, a- high
frequency oscillator connected therewith, an in~
termediate frequency ampli?er connected with
said ?rst detector, a second detector connected
with said intermediate frequency ampli?er, a
pli?er system‘. connected with‘ said’ preselector
circuit, a‘ source ‘of audio frequency oscillation
connected between the grid and cathode of said
high frequency oscillator for continuously
modulating the oscillations-impressed on said
?rst detector at an audio» rate, and a radio' fre
quency by-pass condenser also connected to said 60
grid and cathode, said preselector circuit being
tuned to select the frequency of said ‘source’ of
audio frequency oscillation.
_ 4. A continuous wave radio telegraph receiving
system comprising a superheterodyne receiving
circuit ,including- .a- ?rst detector, 2. high fre
quency oscillator connected therewith, an inter‘
source of audio frequency oscillations. That is mediate frequency ampli?er connected with said
to say, thehigh frequency path from the end of‘ ?rst'detector, aPsecond detector connected with
tuned circuit l5 to the'cathode of tube 4 is closed .said intermediate frequency ampli?er, a pre
selector circuit comprising a variable condenser
through condenser 22 while allowing audio fre
quency oscillations to‘ be impressed from source
I0 upon the input circuit of the'oscillator '4. "
I have found the‘ continuous wave: receivingv
75.:system of my invention highly practical‘ in its:
30
an audio frequency ampli?er system connected
said second detector, an audio frequency am-
from source II! is transferred through the inter
25
with said preselector circuit and a source oflaudio
preselector circuit connected with the output of
mediate frequency ampli?er 5 to the second de
tector 6, audio frequency transformer 20 to pre
60 selector circuit l9 and then to audio frequency
ampli?er ‘I for operation of the indicating device
20
circuit comprising a tunable condenser and a
winding of an audio frequency transformer con
nected with the output of said second detector,
When a continuous wave
' pli?er 5 and at the same time the modulation
15
tector, aqsecond detector connected with said.
intermediate‘ frequency ampli?er, a preselector
incoming signal reaches the oscillator, the beat
or intermediate frequency thereby produced isv
impressed upon the intermediate frequency am
nal is also present.
10
and an inductance connected with the output of
said second detector, an audio‘ frequency ampli
?er system connected with said preselector‘ cir
ouit.. a. source of plate supply for said high fre
2,131,109
quency oscillations, said source supplying energy
for the plate circuits of said ?rst and second de
tectors and said intermediate and audio fre
quency ampli?ers, a source of audio frequency
oscillation connected between the grid and
cathode of said high frequency oscillator for con~
tinuously modulating the oscillations impressed
on said ?rst detector at an audio rate, and means
for bypassing the high frequency oscillations gen~
10 erated by said oscillator around said source of
audio frequency oscillations, said condenser of
said preselector circuit being capable of adjusting
said circuit to the frequency of said audio fre
quency source.
15
5. A continuous wave radio telegraph receiving
system comprising a superheterodyne receiving
circuit including a ?rst detector, a high fre
quency oscillator having a tuned circuit con
nected at one end to the grid of the oscillator,
20 a connection between the other end of said tuned
circuit and the cathode, a transformer having
the secondary winding thereof disposed in said
connection, a source of audio frequency oscilla
tions connected with the primary winding of said
25 transformer, an intermediate frequency ampli
30
35
40
45
50
3
tions generated by said oscillator around said
source of audio frequency oscillations.
7. A continuous wave radio telegraph receiv- '
ing system comprising a superheterodyne re
ceiving circuit including a ?rst detector, a high 5
frequency oscillator having a tuned circuit con
nected at one end to the grid of the oscillator, a
connection between the other end of said tuned
circuit and the cathode, a transformer having the
secondary winding thereof disposed in said con 10
nection, a source of audio frequency oscillations
connected with, the primary winding of said
transformer, an intermediate frequency ampli
?er connected with said ?rst detector, a second
detector connected with said intermediate fre
quency ampli?er, a preselector circuit connected
with said second detector, an audio frequency
ampli?cation system connected with said 'pre
selector circuit, means for adjusting said pre
selector circuit to the frequency of said audio fre
quency source, and a condenser connected across
the secondary winding of said transformer for
forming a closed path for the high frequency os
cillations generated by said oscillator around
said source of audio frequency oscillations.
?er connected with said ?rst detector, a second
detector connected with said intermediate fre
8. In a superheterodyne high-frequency signal
receiving system, in combination, a ?rst detector,
quency ampli?er, a common source of plate sup
a local oscillator coupled with the ?rst detector
for supplying an oscillation to beat with an in
coming continuous wave signal to produce an 3O
intermediate frequency wave, an auxiliary os-'
ply for all stages of said receiving system, a
preselector circuit connected with said second de
tector, and an audio frequency ampli?cation sys
tem connected with said preselector circuit, and
means for adjusting said preselector circuit to
the frequency of said audio frequency source.
6. A continuous wave radio telegraph receiv
ing system comprising a superheterodyne re
ceiving circuit including a ?rst detector, a high
frequency oscillator having a tuned circuit con
nected at one end to the grid of the oscillator, a
connection between the other end of said tuned
circuit and the cathode, a transformer having the
secondary winding thereof disposed in said con
nection, a source of audio frequency oscillations
connected with the primary winding of said
transformer, an intermediate frequency ampli
?er connected with said ?rst detector, a second
detector connected with said intermediate fre
quency ampli?er, a preselector circuit connected
with said second detector, an audio frequency
ampli?cation system connected with said pre
selector circuit, means for adjusting said pre
selector circuit to the frequency of said audio
frequency source, and means connected across
the secondary winding of said transformer form
ing a closed path for the high frequency oscilla
cillator adapted to modulate said local oscillator
at a constant audio frequency, said intermediate
frequency wave being thereby likewise modulated
and having besides the character of the incom
ing continuous wave signal, an intermediate fre
quency ampli?er coupled with said ?rst detector,
a second detector, and an audio frequency ampli
?er peaked at the said audio frequency. ,
9. In a superheterodyne high-frequency con
tinuous wave signal receiving system, in combi
nation, a ?rst detector, a local oscillator, an
intermediate frequency ampli?er, a second de
tector, means for modulating the current in said
intermediate frequency ampli?er at a constant
audible frequency and in the character of the
received signal, said audible frequency modula
tion being detected in said second detector in
the character of the received signal, and an audio
frequency ?lter and a peaked audio frequency
ampli?er for selectively amplifying said modu
lation.
PERCIVAL D. LOWELL.
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