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‘Sept, 11?, 1946.
‘
‘
H. T. BUDENBOM
2,497,54g
DIRECTION FINDING SYSTEM
Filed July 23, 1941
‘
4 Sheets-Sheet l I
INVENTOR
H; 7? BUDENBOM
A from/5y
Sept 37, 3946-
H. T. BUDENBOM
294N549
DIRECTION FINDING SYSTEM
Filed July 25, 1941
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INVENTIOR
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By
HTIBUDENBOM
ATTORNEY
,
Sepit. 3?, 1946, .
> H. T. BUDENBOM
DIRECTION FINDING SYSTEM
Filed July 25, 1941
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O%l:_________
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BY
,
ATTORNEY
Sept 17, 1946'
H. T. BUDENBQM
,
2,407,649
‘DIRECTION FINDING SYSTEM
Filed July 25, 1941
' 4 Sheets-Sheet 4
1.1%“
INVENTOR
'
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Patented Sept. 17, 1946
2,407,549
barren stares PATENT lorries
2,407,649
DIRECTION FINDING SYSTEM
Horace T. Budenbom, Short Hills, N. 3., assignor
to Bell Telephone Laboratories, Incorporated, _
New York, N. Y., a corporation of New York
1
Application July as, 1941, Serial No. 403,693’
9 Claims. (Cl. 250-41)
2
This invention relates to direction ?nders and
particularly to short wave direction ?nders.
In my copending application Serial No. I741,372.
the turntable shaft. Upon proper adjustment of
the collar the zero point of the trace coincides
with the reference line on the cathode tube, the
?led August 25, 1934, there are disclosed a method
positive alternation of the trace being at the left
and means for determining the path or direction
of the line for the front direction and at the right
of an incoming wave utilizing, a pair of spaced . . for the back direction whereby the sense as well
vertical antennas mounted on a turntable and. i as the path of the incoming wave is ascertained.
connected through separate receivers to a cathode
In accordance with another feature of the in
tube phase indicator. Brie?y, the method com
vention, apparatus is added to the phase com
prises rotating the turntable to a position at 10 parison direction ?nding system disclosed in my
which the absorbed antenna energies are in phase _ , copending application mentioned above modi?ed
agreement whereby the plane of the antennas is
or not to include the improvement described
perpendicular to the azimuth direction of the
above, .for continuously maintaining equal gains
incoming wave‘. It now appears desirable to
in the two receiving circuits whereby an aura]
modify the above-described system and in general 155 balance indication may be secured for checking
to secure, in a phase comparison type direction
the cathode tube phase comparison indication.
?nder, an instantaneous indication of the wave
More specifically, each receiver is provided with
direction and, in addition, to provide aural bal- '
a conventional primary automatic volume control
ance means for accurately checking or con?rm~
the direction indication obtained.
t is one object of the invention to determine
for limiting the variation in gain and with a sec
20
accurately, and substantially instantaneously. the
direction of radio waves.
It is another object of this invention to obtain
a continuous indication of the direction and di
rectional sense of an incoming wave irrespective
of changes in said direction.
It is still another object of the invention to
maintain equal gains in the two receiving circuits
of an aural balance direction ?nder.
According to one feature of the invention the
turntable of the direction ?nding system disclosed
in the copending application mentioned above is
continuously rotated at a given low frequency
rate. The in-phase component of the detected 35
audio frequency from one receiver and the quad
rature phase component of the detected audio
ondary volume control for further limiting the
degree of gain variation. In addition, a differ
ential volume control is provided so that, upon a
slight change in the gain of either receiver, the
gain of the other receiver is changed in the same
sense and to the same degree. Preferably, the
various automatic volume control circuits are ?rst
calibrated by receiving a wave emitted by the
local transmitting antenna and adjusting the two
receivers for equal gains. After the initial ad-'
justment the system may be used for obtaining
an aural balance indication for a desired 'wave
incoming from a distant station, the indication
being obtained by rotating the turntable to the
position at which signals having equal amplitudes
and equal phases, as measured by head-phones or
other indicating means, are obtained in the out
puts of the two receivers.
'
The invention will be more fully understood
‘from a perusal of the folowing speci?cation taken
in the output of which a current having a fre 40 in conjunction with the drawings on which like
quency equal to the rotating frequency and a
reference characters denote elements of similar
frequency
conjugate to
of athepush-pull
other receiver
balanced
aredemodulator
supplied
phase related to the direction and sense of the
incoming wave is obtained. The instantaneous
amplitude of the rotating frequency current ob
tained represents the cyclically varying phase re
lation or diiference between the absorbed an
function and on which:
Fig. 1 illustrates
tion for obtaining
parison indication,
ode tube indicator
one embodiment of the inven
an instantaneous phase com
and Figs. 1A and 1B are cath
traces obtained with the sys
tenna energies, and this representative current
tem of Fig. 1;
is applied to the horizontal plates of a cathode
Fig. 2 illustrates an embodiment of the inven
tube indicator. The current for the horizontal
tion for obtaining visual and aural indications of
sweep is obtained from a circular potentiometer 50 the direction of the incoming wave; and
mounted on a collar slidably associated with the
Fig. 3 illustrates a remote indicating arrange
turntable shaft and having a continuously ro
ment which may be used with the systems of
tating contact arm attached to the shaft. A low
Figs. 1 and 2.
I
frequency elliptical trace is obtained which be
Referring to Fig. 1, reference numerals I and
comes a straight line upon proper adjustment of 55 2 designate non-directional vertical receiving
the collar. An azimuth scale is attached to the
antennas and numeral 3 denotes a local trans
collar for use in determining the compass direc
mitting antenna, the antennas being mounted on '
tion of the incoming wave. ‘As an alternative. a
a horizontal turntable 1!. The turntable is sup
sinusoidal trace may be secured by timing a linear
ported by the vertical shaft 5 which is driven or
sweep voltage by means of a synchronizing pulse 60 rotated by the motor 0. Reference numeral 1
obtained from a rotating contact associated with
designates a switch for connecting motor 6 to
2,407,649
3
the power supply leads 8. Antenna 3 is posi
tioned equally distant from, and preferably in
the same plane as, antennas l and 2 and is con
nected through a slip-ring assembly comprising ~
the rotating ring or circular contact 9, insulator
4
No.1 1, as shown on the drawing, one source sup~
plies a sinusoidal current of the rotation fre~
quency and comprises the circular potentiometer
at, the diametrically opposite points 63, 59 of
which are connected, respectively, through con
tacts 5%], 5i, switch 56 and connections 52 to the
opposite terminals of battery 53. The potenti
ometer 41 is rigidly attached to the movable
Antennas I and 2 are each connected through
sleeve 54 which may be manually rotated about
an antenna coupling unit I3, unbalanced line
shaft 5 and locked in a given position by means
conductor M and associated slip-ring assembly 10 of a conventional slot and spring plunger as
to a receiver I5, the receiver I5 connected to
sembly 55. Reference numeral
designates a
antenna I being hereafter referred to as re
transformer having primary winding 51 and sec
ceiver No. I and the receiver I5 associated with
vondary winding 58. The primary winding is con
antenna 2 being hereafter referred to as receiver
nected through contact 59 to a point v6!), equally
No. 2. The horizontal portion of each line con 15 spaced from points to and “is, on potentiometer
ductor I4 is preferably enclosed in a shield I5
til, and to radial arm contact SI which rotates
which forms with the enclosed portion of con
with shaft 5 and sweep potentiometer 47. The
ductor I4 an unbalanced coaxial line. The outer
secondary winding 58 is connected to the input
coaxial conductor I6 is connected to the ground
circuit of a push-pull ampli?er comprising tubes
I‘I. As explained in my copending application,
62 and 63. Reference. numeral M denotes a
the local transmitter 3 is connected to receivers
transformer the primary winding 65 of which is
I5 by the tuning connection 58 and the local
included in the output circuit of the push-pull
transmitter and both receivers are simultaneously
amplifier 82, 83 and the secondary winding 66
tuned by a unicontrol means at the local trans
which is connected to switch 46. Numeral 61
mitter. Reference numeral I9 designates a quad 25 of
designates a conventional azimuth scale assembly
rature phase shifter connected to the output ter
comprising the stationary azimuth scale 58 and
minal of receiver I for the purpose of obtaining at
the rotatable angle scale '65 attached to the sleeve
terminals 28 an audio frequency (as 1090 cycles)
155. As explained below, the cathode tube trace
in-phase potential Fa and at ‘terminals 2! an
is either an ellipse or a straight line.
audio frequency quadrature potential, Fa (90 de 30 obtained
The alternative source of sweep voltage utilized
grees), the potential Fa. and the potential Fb at
with switch 55 in position No. 2 is essentially a
the output terminals of receiver 2 being the in
linear sweep circuit controlled by periodic pulses
phase potentials referred to in the above-men
synchronized with the turntable rotation. Refer
tioned application. As described thus far the
ence numeral ‘i5 designates a linear sweep shap
system is, except for the addition of the slip
ing tube having a cathode 25, a control electrode
ring assembly, similar to that described and
27, screen grid electrode ‘II, suppressor grid elec
claimed in my copending application mentioned
trode ‘I2 and an anode 28 and reference numeral
above.
‘I3 designates a gas-?lled trigger tube having a
The output terminals 22 .of-receiver 2 and the
cathode 26, control grid 27 and an anode 23, the
quadrature output terminals 21 of receiver I are,
tubes being connected in series. Numerals ‘Ill
in accordance with the present invention, con
and ‘I5 designate respectively resistances included
. nected .to the rotation frequency detector 23 which
in the control grid circuits of tubes ‘III and ‘I3
is similar in circuit operation to a vacuum tube
and the numeral ‘I6 designates a by-pass con
wattmeter. The rotation frequency detector
The screen grid ‘II of tube ‘ID and the
comprises tubes 24 and 25 connected in push-pull 45 denser.
control grid 21 of tube ‘I3 are connected through
and eachcontaining a cathode 26, a control elec
resistance 11, spring contact ‘I8 and rotating con
trode or grid 21 and an anode or plate 28. The
tact ‘I9 to the positive terminal of an auxiliary
output terminals 22 of receiver I are connected
battery 80. The radial arm N! is preferably
to the primary winding 29 of transformer 38, the
on or embedded in the circular insulator
secondary winding 3| of which is connected be 50 mounted
SI which is attached to sleeve 54. The anode
tween the grids 21 of tubes 24 and 25; and the
circuit of tube ‘I0 includes a condenser 82, which
quadrature terminals 25 of receiver I are con
is connected through switch 46 to the horizontal
nected to the primary winding 32 of transformer
cathode tube plates 53, and a shunt path com
33, the secondary winding 34 of which is included
in the common lead connecting the ‘grids 2‘! of 55 prising a resistance 3‘! and condenser 83 in series
therewith. Condenser 82 is also shunted by the
tubes 24 and 25 to the cathode 26. vIn other
series path comprising anode resistance 38 and
words, the in-phase output terminals of receiver
the anode-cathode path of trigger tube ‘I3. The
2 and the quadrature phase output terminals of
sweep circuit comprising tubes ‘Ill and 13 and in
receiver I are connected in conjugate in the input
cluding the radial contact ‘I9 is essentially the
circuit of push-pull detector 23. Reference nu 60
same as that disclosed in the RCA Tube Hand
merals 35 and 36 designate respectively a source
book
(tube 884) .
of grid bias potential and asource of anode po
In operation, Fig. 1, wave components incom
tential and numerals 3‘! and 38 denote imped
ing from the distant station and from the local
ances connected respectively in the output cir
cuits of tubes 24 and 25. The output terminals 65 transmitting antenna are, as explained in the
or insulation Ill and the stationary spring con.
tacts H, to the local phasing transmitter I2.
39 of the rotation frequency detector 23 are con
nected by line llil to the horizontal plates 4| of
cathode tube indicator 42.
The sweep or refer
ence voltage applied to cathode tube plates 43
is obtained over. line 613 from the sweep circuit
45.
The sweep circuit 45 includes two distinct
sources of sweep voltage either of which may be
connected by the double-throwlswitch 45 to the
plates 43.
copending application mentioned above, inter
cepted by antennas I and 2 and detected currents
Fa and Pb of a constant audio frequency are
obtained respectively in the output circuits of
receivers I and 2, these components having a
phase relation for agiven orientation of the turn
table related to the direction of the incoming
wave. In accordance with the present inven
tion the turntable is rotated at a very low speed,
for example, one to ?ve revolutions per second,
Assuming switch 46 is in position 75
2,407,649
6
by motor 6 and shaft 5, and as a result the phase '
relation of the radio frequency components of
the incoming distant wave intercepted by an
tennas I and 2, and correspondingly the phase
relation of the two detected currents, are cyc1i~
cally varied at a rate equal to the rotation fre
quency. Thus, when the plane of antennas I
and 2 is perpendicular to the incoming wave
direction the detected currents are in phase, and
when the plane is aligned with the wave direction 10
they have a maximum phase difference. In other
words, during each revolution of the turntable
the phase relation between the detected currents
passes through a zero value twice and through a
maximum or unity value twice. A portion of the
Alternatively, switch 46 may be thrown‘ to
position No. 2 for the purpose of obtaining both
a path indication and a sense indication.
As
suming contacts ‘I8 and 19 are open when the
switch 46 is thrown to position No. 2, the anodes
of tubes 10 and ‘I3 become immediately energized
with positive potential and condenser 32 begins
charging. Since the flow of current from the
anode 28 to the cathode 26 of ,tube ‘I3 is blocked
by the relatively low positive potential on con
trol grid 2‘! obtained from battery 36, the current
from battery 36 flows through condenser 82 and
tube ‘I0 and not through tube ‘I3. The voltage
across condenser 82 is increased gradually, rela
tively considered, and since this voltage is applied
to plates 43 of cathode tube 42 the cathode beam
output of receiver I is shifted 90 degrees by phase
splitter l9 and supplied, as previously indicated,
is simultaneously caused to sweep horizontally in
with the in-phase output of receiver 2 to the
one direction during one revolution of shaft 5.
conjugate input circuit of rotation frequency de
When contacts ‘I8 and ‘I9 close, a high positive
tector 23.
20 potential obtained from auxiliary battery 80 is
As disclosed in Patents 1,586,533 and 2,006,698
impressed through these contacts and resistances
to E, Petersen, granted respectively June 1, 1926,
‘I1 and ‘I5 on the control grid 21 of tube ‘I3 where
and July 2, 1935, the output voltage of the vacuum
upon trigger tube ‘I3 becomes conductive and
tube wattmeter or push-pull detector 23 is pro
condenser 82 abruptly discharges through the
portional to the product of the two input voltages
anode-cathode path of tube ‘I3. At the same
multiplied by the cosine of the phase angle be
time the screen grid ‘II of the shaping tube 18
tween them. When the plane of the antenna is
is rendered more positive so that the discharge
perpendicular to the direction of the incoming
of condenser 82 is accelerated, the function of the
wave the phase angle between the potentials im
shaping tube ‘I6 and associated circuits being to
pressed on grids 21 of tubes 24 and 25 is 90 _
transform in effect the normal exponential dis
degrees, the cosine of which angle is zero, and the
charge characteristic of condenser 82 to a linear
output potential is a minimum. When the plane
characteristic and to secure an ideal saw-tooth
is aligned with the wave direction the phase
angle differs from 90 degrees by a maximum
amount whereby the output potential is a maxi
sweep.
As illustrated by Fig, 1B, with the switch 46
in position No. 2, a sinusoidal trace is obtained,
the position of the positive alternation 86 relative
to reference lines 8? and 88 being indicative of
mum. Hence, there is obtained at terminals 39
and at horizontal plates M of cathode tube 42
a sinusoidal signal voltage having a frequency
the direction and sense of the incoming wave.
equal to the rotation frequency, an instantaneous
Thus, for example, as shown in Fig, 1B, for the
amplitude representing the cyclic variation in the 40 “front” direction the positive alternation 86 is at
phase relation of the above-mentioned absorbed
the right of thevertical reference line 8‘! and
antenna energies and an absolute phase or phase
above the horizontal reference line 88 whereas for
angle related to the direction and sense of the
the “back” direction it is at the left of line 81
incoming wave. Upon a change in the direction
and above line 88. For the side directions per
of the incoming wave the phase angle of they
detected signal current is altered, the frequency
and amplitude remaining unchanged. Stated
pendicularly related to the in-phase direction, it
is symmetrically disposed relative to line 81 but
is above line 88 for the right-hand side direction
differently, upon a wave direction change the
and below line 88 for the left-hand side direction.
sinusoidal wave is shifted on its time axis, with
The sinusoidal trace may be shifted and the azi
.respect to a given point on said axis, an amount .50 muthal bearing ascertained by adjusting sleeve
related to the angular change in the horizontal
54 and the arm ‘I9 attached thereto, and noting
wave direction.
the azimuth scale.
Assuming switch 46 is in position No. 1, the
Fig. 2 illustrates a system which includes sub
potential from battery 53 supplied through con
tacts 56 and 61 and winding 51 is cyclically
varied, a polarity reversal being obtained in effect
stantially the system of Fig. 1 and, in addition,
is provided with means for maintaining equal
gains in the two receivers and for securing an
when arm 6| crosses point 60. This sinusoidal
aural balance, Reference numerals 90 and SI
reference potential is applied to the vertical
designate parallel loop antennas and numerals
plates 43 of tube 42 and, as illustrated by Fig. 1A,
92 designate balanced transmission lines each of
a low frequency elliptical pattern 84 is obtained 60 which is connected to its associated loop antenna
when the potentials have an out of phase rela
through the transformer 93, The parallel loop
tion other than 180 degrees and a straight line
'and balanced line arrangement which is used in
trace 85 is secured when the phase angle differ
place of the vertical antenna and unbalanced'line
ence of the potentials is zero (or 180 degrees).
arrangement included in the system of Fig. 1,
If the trace is elliptical the sleeve 54 may be ad 65 functions in such a way as to eliminate the so
justed until a straight line indication is secured
called “night effect,” as explained on pages 221,
and the angle between the Wave line direction
385, 386 and 389 of the text-book “Wireless Direc
and the chosen reference line direction, as, for
tion Finding," third edition, by R. Keen, since
example, north-south, may be ascertained by ob
the two loops present the same relative aspect to
servation of the azimuth scale 67. The adjust 70 the wave at all times. Loops 98 and 9| are con
ment of sleeve 54 changes for a given orientation
‘nected, respectively, to receivers I and 2 each
of the turntable 4, the position of the radial arm
comprising the radio frequency ampli?er 94 and
6| relative to points 48, 49 and 60 and hence
intermediate frequency ampli?er 95, a portion of
shifts the absolute phase of the reference 0r sweep
the output of which is supplied to a conventional
voltage.
.75 ‘automatic volume control circuit 96 hereinafter
2,407,649
7
referred to as the "primary” automatic volume
control.
Considering each of receivers I and 2, the
greater portion of the intermediate frequency out~
put of ampli?er 95 is supplied over line 9'! and
tube I0 I- of receiver I, whenever the gain of either
receiver is altered the gain of the other receiver
is adjusted in the same sense and to the same
degree. - Hence the gains of the two receivers are
i)
primary winding 98 of transformer 99 to a differ
ential and secondary automatic volume control
circuit IGG. Numeral ISI designates a pentode
tube having its input terminals connected to the
secondary winding I02 of transformer 98 and its
output terminals connected to the primary wind
ings I03 and H54, respectively, of transformers
I65 and I95. The secondary winding IIJ'I of trans_
former I03 is connected to an individual head‘
phone jack 558 and to switch I 09, a phase splitter
I9 being included as in the system of Fig. 1 in the
output circuit of receiver I. In each receiver the
secondary winding I I9 of transformer I93 is con_
nected to a full wave volume control recti?er com
prising tubes I II and H2 and a volume control /
resistance ! i3 included in the circuits of the two
recti?ers. Numerals H4 and H5 designate re
spectively a series resistance and a shunt resist
ance connected together with resistance H3 in
the grid circuit of the differential tube H6, The
anode 28 of tube I IS in each receiver is connected
to the suppressor grid ‘I2 of tube IllI in the other
receiver. Resistance I I3 is also connected by lead
II‘! to the control grid of tube I I]! of the asso
ciated receiver. Hence resistance II3 constitutes
a source of direct current voltage for the differ
ential automatic volume control circuit and a
source of direct current voltage for the secondary
maintained alike and an accurate amplitude bal
ance may be obtained. While the gains are
maintained equal, each varies inversely as the
intensity variation or fading of the incoming dis
tant Wave. If desired, the two receivers may ?rst
be calibrated for equal gain control operation by
receiving the Wave locally emitted by antenna 3
and adjusting the contacts I I8 on resistance I I3,
the transmitter I2 being adjusted so that the
frequency of the locally emitted calibrating wave
is'the same as the frequency of the desired in
coming wave. After preliminary calibration the
frequency of the local transmitter is readjusted
to produce the detected frequencies Fa and Fb
which are utilized in the aural null determination.
The aural null indication is obtained in a man
ner well known in the art. Briefly considered,
with switch I 09, Fig. 2, in position No. l the bear
ing of the distant station, as given by the tube
indicator 42, is noted and the automatic or con
tinuous rotation of the turntable is stopped. The
turntable is then manually rotated as explained
in my copcnding application mentioned above,
to the position at which the line or axis con
necting corresponding points in the two receiv
ing antennas, is perpendicular to the line direc
tion of the incoming wave whereby a phase bal
ance is obtained. As explained above, the volume
control circuits in the two receivers are then
the two receivers are connected to the reference
generator or horizontal sweep circuit 45 and to
adjusted to obtain an amplitude balance. With
the system adjusted for both a phase balance and
an amplitude balance the audible indications ob
tained in the ear pieces connected to jacks I08
the rotation frequency detector 23 for the purpose
are balanced.
automatic volume control circuit,
In operation, with switch I89 in position No. l,
Fig. 3 illustrates apparatus which may be
indication, as explained in connection with Fig. 1. 40 added to the systems of Figs. 1 and 2 for obtain
ing at a cathode tube indicator located many
With the switch I99 thrown, to position No. 2
miles from the turntable either the low frequency
the receivers are connected, as explained in my
elliptical directional pattern, Fig. 1A, or the si
copending application mentioned above to ap
nusoidal pattern, Fig. 1B. For remote indication
paratus for obtaining a high frequency ellipse in
operation, the apparatus of Fig. 3 is inserted, as
dication or a red-green visual indication. An ,
indicated by the dot-dash lines X-—X and Y-Y,
aural balance may, of course, be obtained by
Figs. 1, 2 and 3, in transmission line 40 conveying
means of head-phones connected to jacks I98,
the signal current frequency Ft and transmission
with switch 509 in either position. It should be
line 44 conveying the reference or horizontal
noted that the systems of Figs. 1 and 2 are phase
of obtaining an instantaneous or snap bearing
comparison systems and that in so far as the 50 sweep current Fr or F5 to the cathode tube indi
cathode tube indications are concerned, the pri
mary difference between the two arrangements is
that in the system of Fig. 1 the outputs of two
single non-directional antennas‘ are compared as
to phase, whereas in the system of Fig. 2 the
total outputs of two loop antennas are compared
as to phase.
cator. Referring to Fig. 3, the reference line 44
is connected through a frequency doubler I20 to
the input terminal I2I of the long two-wire tele
phone line I22 and the line 40 is connected to
terminals I2I through the two parallel paths,
one including the frequency tripler I23 and the
voice frequency blocking ?lter I24 and the other
Referring particularly to the volume control
including the voice frequency path ?lter I25. As
circuit I00 the recti?ed voltage drop across re
sistance [I3 in receiver I functions, as is well
known, to vary inversely the gain of tube IIlI
is apparent, line I22 conveys a sweep reference
current of double frequency (ZFR or 2Fs) and a
in receiver I with variable signal, the gain being
decreased as the input signal intensity increases
put terminals I 26 of line I22 are connected to
the horizontal de?ecting plates 43 of the indi
cator 42 through the ?lter I27, which blocks the
and vice versa. Preferably, the primary auto
matic volume control circuit 96 limits the varia
tion in gain to approximately 3 decibels and the
signal current of triple frequency 31%.
The out
passage of voice frequency current and the triple
signal current 3FT, and through the 2 to 1 fre
quency demultiplier I28. Terminals I26 are also
secondary automatic volume control II'I further
connected through the ?lter I29, which blocks the
limits the variation in gain to approximately 1/2
voice frequency current and the reference double
‘decibel or less. Also, since the voltage drop
across resistance H3 connected to the full Wave 70 frequency (ZFR or 2Fs), and through the 3 to l
demultiplier I30, to the vertical de?ecting plates
recti?er III, II2 of receiver I is impressed
4| of the cathode tube 42. The demultipliers I28
through tube II6 on the suppressor grid of tube
and I30 function, respectively, to reduce the
“II of receiver 2, and similarly the drop across
sweep and signal currents to their original fre
resistance II3 included in receiver 2 is impressed
through the tube II6 on the suppressor grid of 75 quency so that the frequency applied to the oath
2,407,649
9
10
ode tube is the same as that used in a local indi
5. A direction ?nder comprising a pair of
spaced independent antennas mounted on a turn
table and positioned to receive a particular in
coming wave, separate detecting means connected
to each antenna for obtaining currents represent
ing the antenna energies, modulating means con
cating system of Figs. 1 and 2. The demulti
pliers may be of any conventional type and pref
erably are of the type described in the article
by R. L. Miller entitled “Fractional-frequency
generators” published in the Proceedings of the
I. R. E., July 1939, page 446. A voice frequency
pass ?lter I3! is included between the line ter
minals I26 and the output terminals I32. The
voice frequency pass ?lters I25 and l3l and as
nected to said separate detecting means for ob
taining from said currents a third current having
a frequency equal to the turntable speed and a
10 phase angle related to the direction of said wave,
generating means for obtaining a fourth current
having a phase angle related to a reference com
sociated shunt paths permit transmission of the
voice frequencies through the system of Fig. 3
without frequency change.
Although the invention has been described in
connection with certain speci?c embodiments 15
pass direction, and means for determining the
phase angle relation between the third and fourth
currents, whereby the direction and sense of the
incoming wave may be ascertained.
6. A direction ?nder comprising a pair of an
apparatus may be successfully used in practicing
tennas spaced for receiving equal intensity com
ponents of an incoming wave, substantially, sepa
the invention without exceeding the scope of the
invention.
20 rate receivers connected to said antennas and
having independent primary automatic gain con
What is claimed is:
1. A direction ?nder comprising a pair of elec
trol circuits, an indicator connected to the out
trically independent spaced antennas for obtain
put of said receivers, and means for compensat
ing separate radio frequency energies from an
ing for the difference in the gain of said receivers
incoming wave, said antennas being positioned 25 comprising a pair of secondary gain control cir
cuits each having its input terminals connected
on a turntable, means for rotating the turntable,
to a different one of said receivers and its output
and producing a cyclically varying phase differ
terminal connected only to the other receiver.
ence between the absorbed antenna energies,
7. A direction ?nder comprising two antennas
means connected to said antennas for obtaining
mounted on a turntable and spaced for receiving
a current representing the amount and sense of
from an incoming wave components having sim
said phase di?‘erence, and means for comparing
the phase angle of said current with that of a
ilar fading characteristics, said antennas being
current representing a predetermined reference
positioned along a horizontal line perpendicularly
related to the vertical plane containing the de
direction.
2. A direction ?nder comprising a pair of re
sired incoming wave, separate receivers each in
cluding an ampli?er and an independent auto
ceiving channels, each including an independent
antenna, for obtaining a pair of currents rep
matic gain control circuit therefor, an aural indi
resenting components of the received wave, means
cator connected to said antennas, and a differ
ential gain control means for changing .the gain
for cyclically moving said antennas at a given
of either ampli?er upon a change in the gain of
frequency in opposite directions with respect to
the other ampli?er, said means comprising a pair
a distant transmitter, means for obtaining from
of recti?ers each of which is connected between
said pair of currents a sinusoidal current having
the output circuit of a different ampli?er and
a frequency equal to said frequency, an ampli
thereof, it is to be understood that it is not to
be limited to these embodiments and that other
only the input circuit of the other ampli?er.
tude representing the phase angle relation of said
8. A method of determining the direction of an
pair of currents and a phase angle representing 45
incoming wave which comprises receiving sepa
the direction and sense of said wave, and means
rate components of said wave, producing in the
for comparing the phase angle of said current
phase-angle relation of the received components
with that of a current representing a predeter
a cyclic variation related to the wave direction,
mined reference direction.
intermodulating said components to obtain a
3. A direction ?nder comprising a pair of inde
sinusoidal current having a phase angle repre
pendent spaced antennas for receiving a given
senting said variation and said direction, obtain
wave, means common to said antennas for cycli
ing a second current having a phase angle repre
cally and oppositely moving said antennas along
the path of said waves, means comprising a mod
senting a reference direction and comparing said
ulator connected through separate receivers to 55 > phase angles.
said antennas for obtaining a current having a
phase angle representing the direction and sense
of said waves and representing the phase rela
tion between the antenna energies, means for ob
taining a current having a phase angle related
to a reference direction, and means for deter
mining the phase angle relation of said currents.
4. A direction ?nder comprising a pair of
spaced vertical loop antennas for receiving a
given wave, said antennas being positioned in
parallel planes and mounted on a turntable for
rotation at a given rate in a horizontal plane,
means comprising separate receivers and con
nected to said antennas for obtaining a current
from the antenna energies having a frequency
dependent upon the turntable speed and a phase
related to the direction of the incoming wave,
means for obtaining another current having a
phase related to a reference direction and means
for comparing the phases of said currents.
9. A method of determining the compass point
direction of an incoming wave, utilizing a pair
of spaced antennas, which comprises receiving on
said antennas a pair of separate components of
said wave, oppositely moving said antennas at a
given cyclic rate relative to said direction to pro
duce a cyclic variation in the phase-angle rela
tion of said received components, obtaining from
the received antenna energies a pair of currents
“ having the same cyclic variation in their phase—
angle relation, modulating said currents to pro~
duce a sinusoidal current having a frequency
equal to said rate and a phase angle representing
said direction, obtaining a reference current hav
ing a frequency equal to said frequency and a
phase angle representing the reference direction
and comparing the phase angles of said last
mentioned currents.
HORACE T. BUDENBOM.
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