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Oct. 8, 1946.
w._ H. BLISS
2,409,012
RADIO RECEIVING SYSTEM
.
Filed Sept. 24, 1942
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#2 PULISE
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WARREN
. BLISS
‘ ATTORNEY
0d. 8, 1946.
w_ H, Buss
2,
,012 ‘
RADIO RECEIVING SYSTEM
Filed Sept. ‘24, 1942
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M17701, Oarpur OFPULSE ésmsparopwrs
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F/AML OUTPUT OF'PULSE' ssmsknroen?é’
ENVENTOR
WARREN H. BLISS
‘BY Hg Z
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W/
ATTORNEY
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Patented Oct. 8, 1946
2,409,012
UNITED STATES PATENT OFFlCE.
2,409,012
RADIO RECEIVING SYSTEM
Warren H. Bliss, Orono, Maine, assignor to Radio
Corporation of America, a corporation of Dela
ware
Application ‘September 24, 1942, SeriallNo. 459,504
11 Claims. (Cl. 250-420)
2
This invention relates broadly to apparatus for
scanning a given frequency band of the radio
spectrum, locating any new signal which appears
therein, and controlling a device for ‘making a
record of such a signal. Reference is herein
made to my copending applications Serial Nos.
455,187 and 457,282, respectively, ?led August 18,
71942, and September 4, 1942, for other inventions
A feature of the invention lies in the system
of comparator device which passes onto the mo
tor‘control circuit for the recording receiver only
those new 'signal‘s'which persist in consecutive
sweeps of the scanning receiver.
Another feature of the invention comprises the
circuit arrangement for stopping the tuning of
the recording receiver at the particular point of
of mine relating to similar subject matter.
the frequency spectrum being scanned at which
In monitoring the radio spectrum for enemy 10 the newly found signals appear.
'
and illegal stations, a transmitter which suddenly
A more detailed description of the invention
goes into action, sends a short message at high
follows in conjunction with'drawings wherein:
speed, and then shuts down quickly is very hard
Fig. 1a and Fig. 1b, taken together, illustrate
to detect.
diagrammatically a vspeci?c embodiment of the
An object of the present invention is to provide 15 invention;
a method of and apparatus for detecting the sig
Fig; 2 graphically illustrates the manner in’
nals from such unknown stations.
which the tuning of the ‘recording receiver is
In brief, the present invention is a scanning
stopped at the particular portion of the frequency
receiver for detecting telegraph stations within
spectrum being scanned at which the newly found
the range of frequencies scanned by the receiver 20 signals appear and
and recording the signals therefrom. For achiev
Fig. 3 graphically illustrates the operation of
ing ‘the results of the ‘invention, ‘there is provided
the 360° phase shifter of Fig. 1.
a superheterodyne receiver which is swept or
Referring to Figs. 1a and 1b in more detail,
tuned rapidly over a ‘given band of frequencies
there is shown a supe'rheterodyne receiver I indi
by means of a sweep device. The output of the 25 cated diagrammatically in box form. The heter
receiver is arranged to be in the form of keyed
odyne oscillator to the receiver (not shown) has
tone whose modulations correspond to the modu
its ‘frequency controlled by a parallel tuned cir
lations of the received signals. This keyed tone
cuit 2. The ‘receiver 1 is designed to receive tele
is supplied to a comparator ‘device in which the
graph signals, and is provided with a suitable tone
signals of the known stations in the band of ‘fre 30 keying ‘circuit for supplying interrupted audio
quencies scanned by the receiver are neutralized
tone whcse'interruptions correspond to the modu
or blanked out, so to speak, by locally generated
lations of the interruptions of the received tele
pulses. To achieve this result, there are provided
graph signals; These keyed tone signals appear
as many local blank-out pulse generators as there
in the output circuit 3‘ of the superhete'rodyne re
are different known stations in the band to be
ceiver for subsequent use in the comparator de
scanned. Thus, the presence ‘of a new'signal sud
vice 4 to be described in more detail later. For
denly appearing in the frequency v‘spectrum being
‘scanned will have no compensating or blank-out
pulse and can be registered on a short loop of
causing the receiver to periodically scan a pre
determined portion of the radio frequency spec
trum, there is provided a reactance tube circuit
magnetic tape which is exactly two sweep cycles 40 5 of a Well-known type, whose anode is connected
in length. This new signal from an unknown
to the tuned oscillatory circuit 2 of the heterodyne
station can then be continuously recorded by
oscillator of the receiver, and whose control grid is
means of a second receiver whose tuning is auto
connected to the output of a sweep device 6 which
matically adjusted by a motor control circuit to
‘generates saw-tooth waves. Since the reactance
the particular position in the frequency ‘band
tube circuit 5 is well known in the frequency mod
being scanned in which the ‘new signal appears.
ulation art for providing a'variable'reactance out
put dependent upon the modulating voltages ap
In order to prevent the second ‘receiver from re
sponding to noise pulses which are random in na
plied to the grid of the device. it is not believed
ture and time of appearance, the motor control
necessary to describe this circuit further.
circuit for the second receiver is controlled by a
The sweep device 6 for generating sawtooth
comparator device. This comparator device will
oscillations comprises, in the particular embodi
ment vshown, a gaseous tube 1 which is arranged
enable the motor control circuit to function, provided the new signals are repeated during con
to ‘rapidly discharge the condenser 8 through the
secutive sweeps of the scanning superheterodyne
space path of the tube after the charge on the
receiver.
condenser 8 has reached a critical value. ‘A vac
2,409,012
3
4
uum tube pentode 9 serves to charge the con
this time, when tube l9 becomes conducting, tube
20 will become non-conducting by virtue of the
denser 8 linearly. A sixty cycle synchronizing
operations. The output of the sweep device 6 is
connected through lead H) to the grid of the re
actance tube 5 to provide sixty cycle saw-tooth
regenerative nature of the feed-back circuit of
the trigger arrangement. The value of con
denser 63 and the value of resistor 62 determines
the time of conduction of tube I9 and hence the
time of duration of the pulse impressed on lead 2|.
waves per second to the reactance tube 5.
Cathode resistor 64 furnishes the common bias
source, labeled as such, assures the breakdown of
the gas tube 1 at a desired point in the cycle of
As a
result of this, the superheterodyne receiver will be
for the grids of both tubes l9 and 20.
caused to scan at a substantially uniform rate a l5)
The particular time of concurrence or position
predetermined portion of the radio frequency
in the sweep cycle of the pulse obtainable from
spectrum, after which the receiver will return to
normal and repeat the scanning operation at the
rate of sixty complete scanning operations per
second. The range of the band of frequencies to
be swept or scanned by the superheterodyne re
ceiver is determined to a large, extent by themag~
nitude of the saw-tooth variations of the sweep
circuit, and the position of the band in the spec
trum is adjustable by the usual controls in the
receiver.
A multiplicity of blank-out pulse generators
with their respective associated phase shifters
are herein designated by the legends #1 pulse
generator and #2 pulse generator. Although
only two generators are shown, there are usu
ally provided as many pulse generators as there
are known stations in the frequency band to
be scanned whose signals are to be blanked out.
If, in the operation of the system, there are more :
pulse generators than known stations, the excess
number of pulse generators may be rendered in
operative by a suitable adjustment in a manner
to be described later. All blank-out pulse gen
erators are connected in parallel to the lead 21. :
Since the pulse generators are identical in con
struction and operation, it is deemed necessary
to describe only one of these, let us say #1 pulse
generator.
the trigger circuit I8 is controlled by adjustment
of the phase shifter 13 and more speci?cally by
the adjustable resistor 24 in the phase shifter.
Since the adjustment of the resistor 24 of the
phase shifter will only provide a variation in po
sition of the pulse obtainable from the trigger l8
over substantially one-hair" or 180° of the sweep
cycle, it thus becomes necesssary to provide
means for changing the position of the pulse in
the sweep cycle over the entire cycle and this is
accomplished by means of the reversing switch
l2 which by its operation enables the adjustable
resistor 24 of the phase shifter to control the po
sition of the pulse obtainable from the trigger
circuit IQ for any desired portion of either of
the two halves of the cycle. It should at this
time be understood that the adjustment of the
position of the pulse obtainable from the pulse
generator is important because this position must
be made to correspond to the position of the sig
nal received from a known station in order to be
able to blank-out the signal from the known sta
tion in the comparator 4. The adjustment oi’
the duration of the blank-out pulse obtainable
from the pulse generator is also important be
cause the duration of the blank-out pulse must
correspond to the duration of the signal received
from the known station. The appearance of the
This pulse generator is supplied with energy 40 blank~out pulse in the lead 2| will cause a rel
from the sixty cycle synchronizing source over
atively negative pulse to be applied to the com
leads I I through reversing switch I2 and phase
parator 4 for reasons which appear hereinafter.
shifter l3. The phase shifter consists of a sixty
As for the comparator 4, this circuit comprises
cycle transformer whose primary winding‘is con
a pair of push-pull vacuum tube ampli?ers 25
vi and 26 operating as class B; that is, normally
nected to the reversing switch I2 and whose sec
ondary winding has shunted across it a con
biased to a point of anode current cut-off. The
denser and a variable resistor 24. The’ junction
grids of these ampli?ers are connected to op
of the condenser and variable resistor is con
posite terminals of the secondary winding of a
nected to the grid of a gaseous discharge device
single input transformer 21 which is designed to
l4 (generally referred to as a “'I'hyratron”) . The
pass the keyed tone appearing in the output cir
center point of the secondary winding of the
cuit 3 of the receiver. The combination of re
sixty cycle transformer is connected to a bias
sistors I58 and [BI give the proper bias for the
resistor l5 which supplies negative bias for the
grids of the tubes 25 and 25 by raising the cathode
grid of the glow tube l4. The condenser l6
potential to a desired amount above ground po
across the'glow tube I4 is arranged to be charged
tential. By making the cathode positive, I in ef
through the variable resistor 11 and to be dis
fect make ‘the grid negative since the grid is tied
charged through the space path of the tube at
down to ground potential. The anodes of the
a sixty cycle rate. The voltage from condenser
tubes 25 and 26 of the comparator 4 are connected
I8 is supplied to a trigger circuit i8 composed
in push-pull to the opposite terminals of audio
of a pair of‘vacuum tube triodes l9 and 20.
output transformer 28, also designed to pass the
Normally, tube 20 is in the state of conduction
tone. In the operation of the comparator 4, the
and tube l9 non-conducting. When a pulse is
vacuum tubes 25 and 26 will normally pass the
impressed on the grid of tube I!) from tube 14, the
alternate half cycles of the tone appearing in
state of conduction of the two tubes 19 and 20
the transformer 21. However, the application of
is reversed. These two tubes, in effect, comprise
a negative blank-out pulse from one of the pulse
a trigger circuit which always tends to be re
generators over lead 2| will supply an additional
stored to the condition where H! is non-conduc
negative bias to the grids of the tubes 25 and 26
tive and 28 is conductive. This restoration takes
which will prevent these tubes from passing cur
place at a short interval after conduction starts
rent during the application of the blank-out pulse
in. tube l9, and is determined by the values of "
resistor 62 and condenser E3. When tube I9 be
comes conducting, its plate potential immediately
drops for the duration of the conduction period,
as a result of which a pulse of negative polarity
is fed back via lead 21 to the comparator 4,.v
_At
even in the presence of tone signals on input
transformer 21. It will thus be seen that by
means of the pulse generators it is possible to
prevent the comparator 4 from passing current
at any particular time and for any desired dura
tion in any sweep cycle.
2,409,012
5
6
The output of'comparator 4 is passed on to a
recorder’ coil ‘65 which is associated with a loop
to the anode and to the grid of tube ‘H_ simulta
neously in order to cause this tube to pass cur
of continuously moving magnetic tape 66.‘ Inthis
rent. Thus‘, only when a newly found signal
way the coil .85 registers signals on tape 66 in
appears (which of course will be repeated dur
response to impulses iwhichipass, through com
parator 4 and which‘ are representative of a new
ing consecutive sweeps of the receiver) will the
comparator!!!) pass current to the motor control
or unblanked signal.
circuit.
>
s
The magnetic tape '65 is continuously driven
,
The motor control circuit ‘80 comprises two
gas triodes (Thyratrons) ‘I8 and 19, both of which
vin the directionindicated by the'arrow by motor
M’ which‘ is synchronously controlled by the same 10 are normally non-conductive. It should be noted
that the path to operate the grid of tube 18 com
sixty cycle source which is associated with the
sweep device 6. Loop ‘66 is exactly two sweep
prises connection 15 and includes the ‘armature
cyclesin length; that'is, the relative speeds of
scanning ofthe receiver l and rotation of loop
‘66 must, be such that the loop of tape '66 ~makes
and normally closed contact of relay ‘ll. Relay
1'! is in the cathode circuit of gaseous conduction
tube 18 while relay '16 is in the anode circuit of
gaseous conduction tube 19. The application of a
positive'pul'se'from the comparator 9D to the lead
one complete circuit while the receiver 'l; sweeps
through a complete ‘sweeprcycle twice. "During
each‘vsweep cycle of the receiver I, a desired por
tion of ‘the radio spectrum to be studied will be
scanned and the receiver will be ready for the
‘next sweepnA magnetic_pick-up coil Q61 'isvlo
15 will cause a voltage to pass through the con
tacts of the relay 1‘! ‘and ignite tube 18 of the mo
20
tor control circuit. This will cause tube 18 to
pass current and operate relay ‘ll. The ‘opera
cated half way around the tape 66 ‘from’ the
recording coil_65 and spaced one complete sweep
tion of the relay" will break the path from the
cycle apart along the‘tape.
this path to the grid ofltube 19. At the same
time, the operation of relay 1''! will connect
,
k n
lead 15 to the grid of the tube 18 and will connect
v
s The pick-up coil "61 is connected to a switch 58
which in one position (namely, ‘the left) can
25
verase the vsign‘alsrecorded on thevtape 66, while
in‘ the other position _(namely, the right-hand
position) passes thepicked up signals to the am—
ground to lead 14 to operate the ,“spotting‘motoF
M, which,_ in turn, causes the conventional
'pli?er 69. n The output of the ampli?er 69 is in
recording receiver 9| to become operative and
change its tuning over the same band of ire
quencies which is being scanned ‘by the super
the form of ampli?ed pulses which have been
het-erodyne receiver I.
v
_
s
_
purpose I of comparator 90 is to prevent noise
The manner in which the tuning of the re
ceiver ‘9| over the band of frequencies‘being
scanned is stopped at the exact point at which the
newly found station appears in the spectrum 'be
ing“ scanned will now be described. Receiver 9|
pulses from being passed on to operate the motor
control circuit 180.“ This second comparator in
is initially tuned to one end of the band of fre
queneies being investigated. The tripping» of the
picked _up ‘by, the pick-up‘ coil 61. 7 These vam
pli?ed pulses are passed‘ on?toya second com
parator ‘90 where they "are recti?ed in, tube 10
and applied to the anode ofatriode ‘H. The
35
‘motor’ control circuit 80' and the consequent op
cludes 'a ‘pair of recti?er tubes 10 and 12, and
also a ‘vacuum tube triode ‘I l.
I _
p ‘
,
40
Any newly foundsignal will appear in the out
put of trans'i‘orrner 128 of the comparator! in the
form of keyed tone pulses. This newly found
signal will be recti?ed in recti?er 12 of the sec
ond comparator and‘i'mpressed upon the grid of
the vacuum tube triode ‘I I, at thesame time that
the signal is applied to the recorder coil ‘65. If
eration of the motor M starts the receiver 9| ‘and
causes the frequency of the {receiver 9| (‘to which
it is initially tuned) tochange'under the drive
of the spotting motor M. The motor-M also
drives the ‘phase shifter'BL over shaft I82 si
47)
multan'eously with the change in tuning vof re
ceiver 9|. This ,phase'shifter Bl is a ‘360°"motor
driv'en'phase shifter. which is‘synchronously con
this newly found signal has appearedin a pre
trolled over leads 8?! from the same sixty cycle
vious sweep cycle, it‘will have been registered
synchronous y “source which synchronizes ‘the
on tape 66.
‘ ‘
When ‘an impulse impressed
on ~' ‘sweep ‘devices and the pulse generators, as'well
as synchronizing the motor v'M'. The phase
recorder coil‘65 corresponds in time to an im
pulse registered on thetape 66 and simultaneous
‘shifter 8| includes “a pair-of potentiometers 9’2
ly picked-up by coil B1,it will be seen that both
and '93 with continuous'resistance elements and
recti?ers ‘l0 and 12 will at ‘the 'sametime be im
sliders S4 and 95'Vth'at 'c'an'rotate 360°. The re
pressing positive potentials on both the grid and
sistance' elements are tapped every 90°. The two
anode ‘electrodes of tube ‘H. This condition will
potentiometer's‘are ‘ganged and arranged so that,
cause the tube ‘H to pass current, as a result of
if corresponding taps are'in line, the "sliders 9'4
which a pulse of vvoltage will be taken off the
'and '95 vare mutually perpendicular. A voltage
cathode of triode ‘ll vand passed on to the motor
from synchronizing leads "82 is applied through
control ‘circuit 80. The comparator #2 serves to ‘c a transformer "91 to terminals C and D on pc
‘prevent'noise from entering the motor control
tentiometer S3, andthe same magnitude of volt
age “applied ‘through 90° phase ‘shifter 98 ‘and
circuit in this way. Since noise is fortuitous and
transformer "99‘ to' terminals ‘A ‘and B on‘the‘ other
random in character, seldom will it appear‘twice
in succession at times one'complete cycle apart.
unit ‘92 butshift‘ed 90° with respect to the ‘volt
age applied to terminals‘ C‘, D._ The output of the
Thus, if noiseappears only'once, there will be a
pulse corresponding to this‘noise'which will pass ,
recti?er "Hand be impressed upon the'g'rid of
vacuum'tube‘ll, ‘but there will not be'a corre
spondingly-timed pulse picked up by coil 61, am
'360°~'phase shifter‘!!! taken from the sliders 9'4
"and 95 is fed‘thro'u‘gh transformer'??‘to the
pulse generator.
‘
r
‘
The vector‘diagram'iof vFig. 3~shows the volt~
pli?ed by‘19, recti?ed by tube» 10 and impressed '
ages’at the taps of‘the twore'sistiveelements.
on the'anode of‘ll. The application of'a’pulse
solely t'o‘thelgrid' or‘ toy the anode of tube ‘II will
not cause this tube ‘to-‘pass current since the‘cir
cuit elements are s'o'constructe'd and designed
Points 0 "and O’ 'on‘both‘elementsare all_ at the
that there is required the application ofvpulses. '
same potential or reference point'as shownjcn
the vector diagram. wAs slider ‘194 "rotates, the
magnitude but not the phaseb-f the voltage which
itpicks up‘varies' fromvector 0A to ‘vectorOB
2,409,012
'7
and backagain to 0A. This is an amplitude var
8
by throwing switch 58 to the left. The opening
iation with no variation in phase. Likewise the
of switch 84 in the motor control circuit will re
voltage from slider 95 varies from O0 to ODand
back to OC.
The output taken through transformer 96 is
store the motor control circuit to normal. By
the vector sum of the slider voltages. This output, indicated as vector OR will have a locus of
means of a manual adjustment (not shown) in
the receiver 9|, this receiver can be returned to
the point of origin of the frequency spectrum be
ing scanned by the receiver I. It should, of
course, be understood that when the receiver 9|
is made to be operative to be tuned over the fre
variation as indicated by the dotted line on Fig. 3.
As the common shaft I82 of the potentiometers
‘92 and 93 is rotated, the phase of vector OR, rep ll) quency band by motor M, the width of the tuning
band of the receiver 9| corresponds to the fre
resenting the output voltage, will advance con
quency spectrum scanned by superheterodyne re
tinuously in the direction of the arrow from its
ceiver l. The 360° phase shifter 8| must also be
initial or reference position 00 and for one com
restored to normal and this can also be done man
plete revolution of this shaft I82 the phase of
the output voltage will change by 360°.
'"
ually by means not shown. In order to place this
system in operation again, the pulse generators
A short pulse generator labeled “#3 Pulse gen
#1 and #2 are reset to blank out the signals cor
erator" is provided which is identical in construc
responding to the known stations during ‘which
.tion and operation to the circuits of #1 pulse'gen
time the switch 68 should be in a position to con
.erator and #2 pulse generator. Initially, the
pulse developed by this #3 pulse generator ap
tinue erasing and after which time the switch 68
should be thrown to the ampli?er position. The
nearing in lead 83 has a phase as indicated bythe
switch 84 in the motor control circuit should now
pulse in line B of Fig. 2. As the phase shifter 8|
be closed.
is driven by the motor M, the position of the
The purpose of the monitor circuit 55 is to en
pulse in the output lead 83 of the #3 pulse gen
able the operator to make suitable adjustments
erator advances over the sweep cycle until such
in the system. This monitor consists of a cathode
time as it coincides in time with a pulse of the
ray oscilloscope 54 having horizontal deflection
newly vfound station. This is indicated in line C
plates 56 and vertical deflection plates 51, to
‘of Fig. 2. The pulses in lead 83 coming from #3
gether with an associated recti?er 5B for applying
pulse generator are impressed on the grid of tube
recti?ed pulses to one of the vertical de?ection
19 of the motor control circuit 89. As long as
plates 5?. The anode of the recti?er 5B is con
the pulse of the newly found signal appearing in
nected to the armature of a switch 59 by means
lead 15 does not coincide in time ‘with the pulse
of which the recti?er can be connected either
appearing in lead 93, ‘tube 19 will remain non
directly to the keyed tone output circuit 3 of the
conductive. When, however, a pulse in lead 83
superheterodyne receiver by means of lead 60,
coincides in time phase with a pulse appearing
or directly to the output of the comparator device
in lead 15 from the output of comparator 90, it
4 by means of lead 6|. Thus, the attendant is
will be seen that both pulses will be impressed on
able to observe at a glance by suitably operating
the grid of gas triode ‘I9 simultaneously. Since
the switch 59, the appearance of the pulses in
these pulses ‘are positive, the simultaneous ap
pearance of both pulses in leads 15 and 83 will (l O the output of the superheterodyne receiver 3 and
also the appearance of the pulses in the output
ignite tube 19, as a result of which relay 16 will
of the comparator 4. ‘If the system is properly
operate. The operation of relay 16 will break the
adjusted, the keyed tone pulses ‘appearing in the
anode circuit of tube 78, thus extinguishing the
output of the superheterodyne receiver I will not
arc in tube 18 and causing relay '1‘! to release. It
appear in the output of the comparator 4, except
‘is assumed, of course, that the manually op- L
for the signals corresponding to those from the
.erated switch 84 supplying positive polarizing
potentials to gas tubes 18 and 19 is normally
closed during all this time, it being opened only
unknown or newly found station.
A general description of the operation of the
system as a whole will now be given, Sweep
device
causes the frequency of hunting re
ceiver | to sweep over a given predetermined band
when it isldesired to restore the complete circuit
to normal. The release of relay 11 will open its
right-hand contact, thus stopping the motor M at
width. The‘panorama of signals in this band will
a point ‘which corresponds to the point at which
be observed on cathode ray monitorili
the re
;the newly found signal appears in the frequency
ceiver sweeps repeatedly over the band, By
spectrum. The tuning of the receiver 9| will be
means of phase shifters l3 and pulse generators
stopped at this point in the radio frequency spec~
trum. The standard code recorder 85 which op
#1 and #2. and additional such units as needed,
erates continuously from the time receiver 9| is
the pulses in the output of receiver | represent
made to be operative by the ‘motor M, will now
ing the presence of normal signals from known
record the signals of the newly found station
stations are cancelled out in comparator 4. The
collected by receiver 9| over antenna I92. Put 60 output of comparator 4, which is registered on
ting it in other words, it will‘be seen that since the
magnetic loop 68, will then consist only of noise
phase of the pulse from comparator 90 is an in
pulses. if present, and any new signals which may
dication of the position of the new station in the
appear. In the case of random noise pulses, com
spectrum, and the phase of the pulse from #3
parator 99 will not respond. In the case of sig
pulse generator isan indication of the frequency
of the receiver 9|, the matching of these pulses
will match the frequency of receiver 9| to that
of the desired signals. It should be noted the
although receiver 9| is tuned to the frequency of
nals from a new station, hoWeven-these are regis
tered on the tape and comparator 90 will func
tion because of the presence of simultaneous
pulses from the receiver 1 and pick-up coil 61.
The comparator 90 passes the newly found sig
,the newly found signal within the spectrum being 70 nals on to motor control unit 80 which places
scanned, thesuperheterodyne receiver I will con
spotting motor M into operation for simultane
tinue scanning.
ously rotating phase shifter 8| and moving the
To restore the entire system to normal, in order
tuning of recording receiver 9|. As the motor
to hunt for another new station, the registra
M rotates, the phase of the local pulse generated
tions on the magnetic tape 66 should be erased 75 1by #3 pulse generator .will advance and ?nally
2,409,012
be in time phase with the received pulse coming
over lead 15 at which time motor M will stop,
thus causing the tuning of the recording receiver
9li to stop in the proper position for this last re
ceiver to pick-up the new signals and record
them in apparatus 85., Receiver 91 will remain
tuned to the frequency of the new signals until
10
sponsive, to a voltage pulse in said connection for
operating, saidmotor to change the tuning of said
second receiver over said selected band of fre
quencies.
> 4. In a telegraph receiving system, a, ?rst re
ceiver, means for periodically tuning the receiver
over a'selected band of frequencies, a local pulse
generator, means for combining the pulses from
an attendant, or other means notv indicated,
said'generator with the output of said receiver,
changes the tuning. In summation, the oper
whereby signals from a known station appearing
,ation consists of the following fundamental steps: 10 in the‘output of said receiver may be blanked
(1) A given portionof the radio spectrum is re
out, a moving magnetic loop synchronously
peatedly scanned for the presence of signals, (2)
driven with relation to the scanning of said re
all signals in the selected portion or the spectrum
ceiver for registering new signals in the output
are investigated and balanced out by locally gen
of said receiver, a comparator circuit responsive
erated pulses, (3) the appearance of new signals 15 solely to a new signal which appears in said re
is investigated, and if they persist (4) a new re
ceiver and to the registration of said new signal
ceiver is automatically tuned to the frequency of
from a previous cycle of scanning for producing
the new signals so that they may be recorded,
a voltage pulse of desired polarity, a second re
and (5) the effect of noise peaks is eliminated.
ceiver adapted tobe tuned over said selected band
20
It should be understood that it is within the
of frequencies, a motor to change the tuning of
contemplation of the invention to change the
the second receiver, a motor controlcircui-t for
scanning rate and the width of the portion of the
said motor, a connection from said comparator
radio spectrum to be scanned at the will of the
.to
said motorv control circuit, said motor control
operator. The scanning rate can most easily
circuit being so constructed andv arranged as to
be changed by changing the fundamental fre 25 be responsive to a voltage pulse in said connec
quency of the sweep device and the pulse gen
tion for operating said motor to change the tun
erators.
ing, of said second receiver over said’ selected
Whatis claimed is:
band of frequencies, another local pulse gen
1. In a telegraph receiving system, a ?rst re- 30 erator, a rotatable phase shifter for said last
ceiver, means for periodically tuning the receiver
over a selected band of frequencies, a local pulse
.pulse generator, a shaft for driving said phase
shifter from said motor simultaneously with the
change in tuningrof said second receiver, said
motor control circuit including circuit elements
generator, means for combining the pulses from
said generator with the output of said receiver,
whereby signals from a known station appearing
responsive to the simultaneous appearance of a
in the output of said receiver may be blanked out, 35 voltage pulse on said connection and a voltage
a second receiver, a recorder in circuit with said
pulse from said last, local generator for stopping
second receiver, and means responsive to new sig
said motor at a point which leaves said second
nals in the output of said ?rst receiver for caus
receiver properly tuned to pick up the new signals.
ing said second receiver to tune to the frequency
5. In a radio signal receiving circuit, a ?rst
40
of the new signals.
,
receiver, means for periodically tuning said ?rst
2. In a telegraph receiving system, a ?rst re
ceiver, means for periodically tuning the receiver
over a selected, band of frequencies, a-local pulse
generator, means for combining the pulses from
said generator with the output of said receiver,
whereby signals from a known station appearing
in the output of said receiver may be blanked out,
a second‘ receiver, a recorder in circuit withsaid
second receiver, and circuit means responsive to
new signals in, the. output of said ?rst receiver
which persist for a plurality of consecutive sweep
cycles of said ?rst receiver for automatically tun
ing said secondireceiver to the frequency of the
new signals.
‘
3. In atelegraph receiving system, a ?rst re
receiver over a selected band of frequencies, a
second receiver adapted to be tuned over said
same selected band of frequencies, and means for
_- changing the tuning, of said second receiver over
said band in synchronism with said ?rst receiver
including a signal comparator circuit which is
responsive solely to the presence of signals to be
detected which appear a predetermined number
50 of vtimes over successive cycles of tuning of the
?rst receiver.
6. In a telegraph radio receiving system, a, ?rst
receiver, means for periodically tuning the re
ceiver over a selected band of'frequencies, local
55 pulse generator means having circuit elements
for adjusting the position and width of the pulse
generated in each cycle, connections for com
over a selected band‘of frequencies, a local pulse
bining the pulses from said local generator means
generator, means for combining the pulses from
with the output of said receiver, whereby signals
said generator with the output of said receiver,
from known stations in said band can be blanked
60
whereby signals from a known station appearing
out, a second’ receiver‘ adapted to be tuned over
ceiver, means for periodically tuning the receiver
in the output of said receiver may be blanked out,
said same selected band, and means for changing
a moving magnetic loop synchronously driven
the tuning of said second receiver over said band
with relation to the scanning of said receiver for
in synchronism with said ?rst receiver including
registering new signals in the output of said re
65 a signal comparator circuit which is responsive
ceiver, a comparator circuit responsive solely to
solely to the presence of signals to be detected
a new signal which appears in said receiver and
which appear a predetermined number of times
to the registration of said new signal from a pre
over successive cycles of tuning of the ?rst re
vious cycle of scanning for producing a voltage
ceiver.
pulse of desired polarity, a second receiver adapt
7. In a radio receiving system, means for pe
ed to be tuned over said selected band of fre 70
riodically tuning the receiving circuit over a se
quencies, a motor to change the tuning of the
lected band of frequencies, means for converting
second receiver, a motor control circuit for said
the received signals to keyed tone output signals,
motor, a connection from said comparator to said
an ampli?er for passing the tone signal output of
motor control circuit, said motor control circuit
being so constructed and arranged as to be re 75 said receiver, a plurality of pulse generators,
11
2,409,012
12
means for synchronously operating all of said
over a predetermined portion of the ‘radio fre
pulse generators in timed relation with said pe
quency spectrum, an element for storing a charge
riodic tuning means, said pulse generators hav
representative of a signal pulse received by said
ing means for adjusting the position and the
receiver from the telegraph station to be detected
width of the pulses generated thereby in each
within said spectrum, an evacuated electron dis
tuning cycle, a connection from each of said pulse
charge device having a cathode, an anode elec
generators to the input circuit of said ampli?er
trode and a control electrode, a circuit for im
‘for supplying said ampli?er with pulses of such
pressing upon one of said electrodes of said dis
polarity as to bias said ampli?er beyond anode
current cut-01f during the occurrence of said 10 charge device a positive voltage pulse represen
tative of the stored charge, and a circuit from
pulses, whereby keyed tone output signals from
the output of said receiver to said other electrode
said receiver corresponding to signals received
of said discharge device for impressing thereupon
from known stations can be prevented from pass
a positive voltage pulse representative of a sub
ing through said ampli?er, a recording system
for registering signals from new stations received 15 sequent signal pulse received by said receiver
from the telegraph station to be detected, means
by said receiver, a, signal comparator circuit re
for normally biasing said control electrode to such
sponsive solely to signals registered on said re
a value that said discharge device becomes re
cording system and to correspondingly time
sponsive solely upon the simultaneous applica
phased new signals appearing in succeeding sweep
cycles of said ?rst receiver for producing a pulse 20 tion of voltage pulses to said anode and control
electrodes, a trigger circuit in the form of a gase
of voltage, a second receiver adapted to be tuned
ous grid-controlled tube, and a connection from
over said selected band of frequencies, a motor
the grid of said gaseous tube to the cathode of
to change the tuning of said second receiver, a
said
evacuated electron discharge device, where
motor control circuit for said motor, a connection
by the conductivity of said evacuated device ig
from said signal comparator circuit to said motor
nites said gaseous tube.
control circuit, said motor control ‘circuit being
10. In a radio receiving system, a receiver
so constructed and arranged as to be responsive
which is tunable over a selected band of fre
to a voltage pulse in said connection for operating
quencies, a second receiver. a signal storage ele
said motor to change the tuning of said second
ment, a signal comparator circuit coupled both
receiver over said selected band ‘of frequencies.
an to said ?rst receiver and said storage element for
8. A radio receiving system for detecting un
comparing the time phase of recurring signals re~
known radio telegraph transmitting stations
ceived by said ?rst receiver, circuit means includ
comprising a receiver, means for continually and
ing a motor for changing the tuning of said sec
repeatedly changing the receiver response band
ond receiver, means for coupling said circuit
over a predetermined portion of the radio fre
means to the output of said signal comparator
quency spectrum, an element for storing a charge
circuit, said, signal comparator circuit being so
representative of a signal pulse received by said
constructed and arranged as to pass a pulse to
receiver from the telegraph station to be detected
said circuit means for operating the same only
within said spectrum, an electron discharge de—
vice having an anode electrode and a control 4.0 when received recurring signals appear a prede
termined number of times within a certain inter
electrode, a circuit for impressing upon one of
val of time.
said electrodes of said discharge device a positive
11. In a radio receiving system, a receiver
voltage pulse representative of the stored charge,
which is tunable over a selected band of fre
and, a circuit from the output of said receiver
quencies and which is normally tuned to a prede
to said other electrode of saiddischarge device for
impressing thereupon a positive, voltage pulse
representative of a subsequent signal pulse re
termined frequency within said band, means au~
tornatically responsive to recurring signals with
in said selected band of frequencies and emanat
ing from a remote point for changing the tuning
control electrode to such a value that said dis 50 of said receiver over said band, a signal com
parator circuit for comparing the time phase of
charge device becomes responsive solely upon the
said recurring signals, said signal comparator cir
simultaneous application of voltage pulses to said
cuit being so constructed and arranged as to pre
anode and control electrodes, and a normally
vent operation of said means until said signals
non-conductive translation device coupled to said
appear a predetermined number of times within
discharge device and arranged to become conduc
a certain interval of time, and means including
tive upon the passage of currentin said discharge
a local pulse generator and a rotatable phase
device.
shifter in circuit therewith for stopping the
9. A radio receiving system for detecting un
change in tuning of said receiver at the frequency
known radio telegraph transmitting stations
comprising a receiver, means for continually and 60 position of said signals.
ceived by said receiver from the telegraph station
to be detected, means for normally biasing said
repeatedly changing the receiver response band
WARREN H. BLISS.
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