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Патент USA US2390489

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Dec. 11, 1945.
2 Sheets-Sheet 1
Filed June 21, 1945
2,39048 7 ‘
‘ 62019615.?CZrc/zenbmm
Patented Dec. 11, 1945
George ‘Edward Archenbronn, Chicago, Ill., use
signor, by mesne assignments, to Belmont Radio‘
Corporation, Chicago, 111., a corporation of Illi- '
Application June-21, 1943, Serial No. 491,614
1 Claim.
(01. 250—36)
rI'he present invention relates to variable high
frequency attenuating devices and more particu
larly to an improved arrangement for variably
attenuating the signal energy transfer between
the output circuit of a highfrequency signal gen
erator or the like and the pickup circuit of ap
paratus in which the transferred signal energy
size of the opening through which the two ele
ments are intercoupled.
The invention, both as to its organization and
method of operation, together with further ob
jects and advantages thereof, will best be under
stood by reference to the following speci?cation
‘taken in connection with the accompanying
drawings, in which:
is to be utilized.
Fig. 1 illustrates in schematic form a signal
In certain applications it is necessary to utilize
and associated pickup facilities having
signal generators, which are capable of produc
a variable attenuation
ing a radio frequency voltage which may be un
device characterized by the features of the pres;
modulated, pulse modulated at a ?xed but ad
ent invention;
justable audio rate, or modulated with an audio
Fig. 2 is a top perspective view illustrating the
voltage of ?xed but adjustable audio frequency.
These applications usually'requir'e that the signal 15 mechanical construction and arrangement of the
apparatus schematically shown in Fig. 1;
energy delivered by the generator to the utiliza
Fig. 3 is an end view of the attenuating de
tion circuit be variable within rather wide limits.
To meet this requirement-‘the usual practice is
vice provided in the apparatus;
is required; to operate the generator continuous-
and disassembled relationship, theelements of
Figs. 4 and 5 are sectional views takenralong
that of providing a generator capable of produc
line 4-4 of Fig. 3 illustrating in assembled
ing a signal energy output‘ exceeding that which
ly at its maximum output; and to provide facili~
' ties for variably attenuating the energy transfer
the attenuating device shown in Fig. 3;
Fig. 6 is a curve illustrating the operating char
acteristics of the attenuating device; and
from the generator to the energy utilizing cir
Fig. 7 is a front plan view of the control panel
cuit. Various expedients have been resorted to 25 forming
a part of the assembly shown in Fig. 2.
in attempts to obtain the desired attenuation, all
Referring now to the drawings, and more par¢
of which are somewhat complicated in character
ticularly to Fig. 1 thereof, the invention is illus
and are limited in the obtainable attenuation
trated in its embodiment in a signal generator
30 for the purpose of attenuating the signal energy
It is an object of the present invention, there—
transfer between the output side of the generator
fore, to provide an improved and exceedingly
and an associated pickup circuit. In brief, the
simple arrangement for variably attenuating the
illustrated signal generator comprises a multi
energy transfer from a source of high frequency
vibrator or modulating stage. I 0, an audio fre
current to an associated pickup circuit.
35 quency ampli?er II and a radio frequency car
In accordance with another object of the in
rier producing oscillator l2 connected in tandem
vention, an improved variable attenuating de
in the order named. The audio frequency am
vice is provided having an exceedingly wide
pli?er H and the multi-vibrator or modulating
range of attenuation.
stage 10 are entirely conventional in character
According to a further and more specific object
40 and, accordingly, have been only schematically
of the invention, the output circuit of a high fre
quency generator is provided with an output in
ductance which is coupled to the pickup in
ductance of the utilization circuit through an
It is pointed, out, however, that
these two stages of the generator are arranged
for plate circuit control of the oscillator l2 and
include facilities for either pulse modulating the
opening in one wall of the shielding housing for 45
radio frequency output of the oscillator, or con
the high frequency section of,» the generator, and
tinuously modulating the generated radio fre
improved facilities are provided for variably clos
quency output of the oscillator at a ?xed but
ing the opening in order to vary the coupling
adjustable audio frequency rate. To this end,
between the two inductance elements and thus
suitable switching facilities are provided for rear
variably attenuate the energy transfer therebe-' 50 ranging the circuit elements of the two stages Ill
In accordance ‘with still another object of the
invention, an improved arrangement is pro
vided for minimizing stray coupling between the
two inductance elements, thereby to render the
obtained coupling directly dependent upon the -
and II so that either type of modulation of the
signal ouput from the oscillator I2 ‘is produced.
Additional switching facilities are provided for
changing the circuit constants of the'modula
tion frequency determining circuits ‘provided in
the multi-vibrator It! so that the oscillator out
put may be either unmodulated or may be sub
spaced-apart relation from the front housing wall
24a through which the two inductance elements
jected to pulse or continuous modulation at as
many as four different frequencies.
23 and 28 are coupled. All circuit elements of the
oscillator I 2 are disposed within the conductive
Brie?y considered, the oscillator I 2 comprises
a three-electrode electron discharge tube l3 hav
ing its anode and-cathode coupledrto lithe-output
side of the audio frequency ampli?er H through
the lower section Ma of a tank circuit inductance
element 14. The upper section Nb of the inductg.
ance element I 4 is connected between the cathode
and grid of the tube I 3 through-a gridvleak and‘
housing 24 and a suitable conductive lid, not
shown, is provided for closing the top of the hous
ing. in the completed generator; assembly. Thus,
the _osci1lator._tube l3 isamounted upon a socket
which is supported upon the top wall of the chassis
within the Walls of the housing 24; the frequency
adjusting condenser I9 is supported upon the
inner side~ ofthe front wall 24a of the housing;
condenser network l6 which?comprisespthe leak‘,
the tuning inductance element I4 is appropriately
resistor l1 and shunt connected?lcondenser >|8_._.
supported betweenthe rear wall of the housing,
theucathodeilterrninal of the tube socket and one
For the purpose of variably. tuning the inductance:
element l4 so that the oscillator will oscillate at
any desired radio frequency ‘within at desired _
terminal of theyfriequency adjusting condenser
I 9; and the ends of the output inductance ele
ment~23are~ soldered to the inductance element
range, a variable tuning condenser 191 is provided ~
which is connected between a point 28 alonggthe
inductance element and ground. The output cir
l4 ‘and the front housing wall 24a so ‘that the
single turn thereof is aligned with the opening
cuit of=the audidfre'quency ampli?er-‘H is by
passed for radio frequencyeurrents bycmeansof
a. condenser 2L‘: From the‘ above explanation; it
241); 'I'herremainingcircuitelements of the gen
eratondncluding the elementsof-a suitable-power
pack: and theielements- of the-two stages “land
will ‘beaunderstood ‘that the ‘ oscillator - i2: ‘is - :in
It, aredisposed outside of [the housing grand
the/nature of a conventional Hartley oscillator
arranged for plate circuit-‘modulation; “The: out
certain thereof are disposed within the compart
ment' de?ned: by the base 30ai of-the chassis-30;
As 'bB’St'IShO'WII in‘ Fig. 7 *of the drawingsythe
control elements for the switching‘ apparatus
which ‘is utilized to-fcondition the equipment for
put :'voltage from. this-oscillator is'deri'ved bytap?
ping the inductance element 14 iatca point-‘212
therealong v and shunting the lowermost section
I40 of this“ inductance element‘ with ‘an. output 30
operation; ‘ to selectively arrange the equipment
inductance element-23. As will? be apparent from
for" pulse or; audio frequency modulation of the
Figs: 1 and :2 of‘ theldrawin‘ga'all ‘elements of the
outputvoltage-and toa-vary the pulse or continu;
high frequency oscillator l2, includingthe-out
,modulationlvfrequencyV are :all-extended
put inductance element‘ 23;:aare providedwithin
through the front‘con-trol panel 3!?‘ of the chassis
a ‘conductive'housing -24_-which~is.maintained at ' >
for'easy manipulation by an operator. “ Thesecon
the reference ground potential andaacts to shield
include the actuating armof ‘anon
the elementsgof. the osciliatorzvagainst ; stray-cou
offswitch v3ft, thev actuating arm ofa switch¢33
pling -with extraneousgx,circuits;iand‘ ;cu_rre7nt
which iszutilized selectively toicondition the ap
paratus for‘ pulse: ror'audio frequency modulation
ofiithe; outputwoltage,v -' and- the’ ‘actuating knob
ofza ?ver-position rotary switch T341 which'iisfuth
lized» selectively‘ to rearrange the-circuit elements
» Fort-the ,purpose'ofutransferring renerg-yd’rom
theoutputinductanceelement 23'of,~_the<genera-tor
to a utilization circuitxa ' pickup arrangement I is
provided’ which includes-two.’ connectors 25c ‘and
25b_ two shielded‘ conductors'?a and 21a; and- a
pickupinductance-element 28-, ‘the ; terminal: ends
of which are connected respectively to the adiae
cent ends ofthe conductors 1251a’ and --2T'a.; rThe
of‘ ,the- mul-tiwibraton I0 so ‘that an .unmodulated
signalivoltageorn a modulated rvoltagea of any» one
of four different frequencies isi'produced? by-the
generator The ?vemdi-fferent- positions of-the.
switch 34v arerespe'ctively indicated by a scale 340.
two inductance .- elements. ‘23,- and -:28: which: may
which ‘is arranged to be indexed by a pointer car
eachzcomprise only ‘a single turnat ; thev frequene
cleszinvolvedv, are dispQsedi-n parallel-planes and "50 ried by the actuating knob for the switch." The
frontcontrol panel 3 I‘~ of :the chassis 30 alsorhas
in ‘proximity to each: Other upon eithei-Yside 'of'ithe
an opening therein through which ‘the rotor shaft
housingi-wall Mat, They are mutually coupled
of anadjustable tuning condenser: l 9 extends, this
through an opening Mbmrovided in this housing
shaft being provided at its: extended end vwithan I
wall and having-"a center which is-substantially
axial-alignment with. the; centers-10f,v the-(two
elements», Primarily, the magnetic’ or - mutu ailin
actuating :knob ~.35:s':having-¢a --pointer ‘assembly
55 mounted thereon which‘is arrangedtonoact with
ductive coupling. betweentheitwo elements 23 and
a. suitablycalibrated: scale 535a. to indicate the
28 is: .relied .,upon= to obtain r, the desired energy
I2 is tuned.
transfer between thegoutput. side. of the oscillator
and. the-utilization circuit. in which-the pickup
element 28ii=iprovided~ Accordingly,».n.eces~ V
sary to, providei facilities for suitably attenuating
or varyingthiscouplin-gin order to adjust-the en‘
ergy transfer :between the. two [inductance sele
rnents... ' To this. end, an adjustable rotor = plate, 29
is: provided vfor. variably clcsinggthe, opening ‘24b
output carrier frequency to: which = the. ‘ oscillator
Referring ‘now more particularly :to the :me-,
chanical, construction‘- and; arrangement of :the
pickupefacilities : to which'signal energy-is‘ trans
ferred- from the output inductance element 23 of
the signal- generator,‘ it iwillgbe' noted ‘that the
two-connectors “wand: Z‘Shjareof the female‘
type and are suitably ‘supported upon the.‘ front
control panel -3 l. of the .cha-ssistciillby means of v
assembly screwsor ,theslikei _-'I’1116SQ;1;W0 connec
tors; are respectively provide =. with tubular ele
As indicated above‘. the mechanical-construc
tion andv arrangement‘of the'signal generator and 70 ments which are-disposed rearwardly of‘v the panel
3!, and respectively terminate and support oppo
its; associated pickup facilities-ere illustrated in
site ends of tubular metal shielding elements 26
and 21 within which i the conductors-16a and‘ 21a
upon "a metal chassis 30 which islpro
are supported ; gby- .tmeans; :of. suitable insulating
disks“ The inner-tends ofqthese two tubular ele
pariel SL-arrangeQ-in '75 merits 26, and 21. extendlbetweemthe innensun
face of the panel 3| and the outer surface of
the housing wall 24a, and are suitably joined by
means of a tubular metal sleeve 36.
This sleeve
is ‘provided with a slot in the wall thereof which‘
faces the housing wall 24a, whereby the ends of
the pickup coil 28 may be connected to the inner
cable conductors 26a, and 21a.
Brie?y to consider the mechanical construc
tion and arrangement of the assembly for rotat
ably supporting the rotor plate 29 upon the front
wall 24a of the conductive housing 24, it is point
ed ‘out that this assembly comprises a sleeve 31
having a hub of reduced diameter upon which
the rotor plate 29 is rigidly mounted. This sleeve
is rigidly mounted upon an operating shaft 38
by means of a set screw 31a, and the shaft 38
is joumaled in a bearing 39 rigidly mounted upon
the front wall 24a within the housing 24. The
operating end of the shaft 38 extends through
an opening 43 drilled through the control panel
3| and is adapted to receive an actuating knob 4!
which is mounted upon the shaft end by means
of a set screw 42.
Suitably calibrated scales Ma
and 4lb may be provided in indexing relation
ship with a pointer carried by the knob 4| in
order to indicate the extent of attenuation ob
tained at any given setting of the rotor plate 29.
For the purpose of retaining the enumerated
parts of the rotor plate assembly in the desired
assembled relationship, three assembly washers
43, 44 and 45 are provided, the first of which is
of the split ring type and is adapted to be re
tained within an annular slot formed at the inner
end of the shaft 38. The second washer 44 is
strictly a friction washer and is adapted to en
gage the outer convex surface of the ‘dish-shaped
washer 45. The third washer 45 is adapted to be
?attened during the assembly operation, for the
purpose of spring biasing the control shaft 38 to
face of the rotor plate 29 is held in abutting con
tact with the outer surface of the ?ange 240 due
to the spring bias exerted axially along the shaft
38 by means of the dished biasing washer 45.
Thus the arrangement is such that all portions
of the ?anged edge 240 are held in tight engage
ment with the adjacent surface of the rotor plate
29, regardless of the position to which this rotor
plate is adjusted through rotation of the knob
and shaft assembly 4|, 38. In order to improve
the electrical contact between the engaged sur
faces of the ?ange 24c and the rotor plate 29, a
heavy coating of silver or other precious metal
contact material is provided on the outer annu
lar surface of the ?ange 24c and at all points
within the area of the rotor plate surface which
may engage the plated surface of the ?ange 24c
during rotation of this plate.
For the purpose of limiting the extent of rota
tion of the rotor plate 29, a suitable stop mecha
nism is provided which includes a stop pin 48
mounted upon the housing wall 24a and extend-‘
ing outwardly therefrom through an annular slot
49 cut in the rotor plate 29 concentrically about
the center of rotation of this plate. The pin 48
is so positioned along the front housing wall 24a
that when engaged by the end 49a of the slot
49, the opening 24b is substantially entirely closed
by the rotor plate 29. At the other extreme posi
tion of the rotor plate 29, i. e. that position where
in the stop pin 48 engages the slot end 49b, the
enlarged end portion 41d of the slot 41 overlies
the opening 24b, but the edge 41c of this slot is
removed a substantial distance from the adjacent
edge of the opening 241). The stoppage of the slot
edge at a point removed from the edge of the
opening 241) is necessary in order to prevent the
approaching end portion of the slot edge from
producing rather a sharp change in the coupling
the left as viewed in Figs. 4 and 5 of the draw
between the two inductance elements with a re
ings, and is utilized to maintain the rotor plate
in engagement with the housing wall 24a, there
by to minimize stray coupling between the two
inductance elements 23 and 29 in the manner
more fully explained below.
sulting distortion of the attenuation curve char
acterizing the degree of energyv transfer between
As "best shown in Figs. 2 and 3 of the drawings,
the rotor plate 29 extends within the lower com
partment of the chassis 30 through a slot 46 cut
in the top wall of the chassis, and overlies the
opening 241) of the housing wall 24a through
which the two inductance elements 23 and 28 are
' the two elements.
In considering the operation of the apparatus
described above, it will be understood that con
nections from the signal generator to a signal
utilization circuit may be made by appropriately
plugging male type of connectors into the‘ female
connectors 25a and 25b. Also, by suitable ma
nipulation of the switch 33, the switch 34 and
the condenser adjusting knob 35, the equipment
may be conditioned to generate, at any desired
carrier frequency, an unmodulated radio fre
quency carrier voltage, a carrier voltage which is
pulse modulated at a desired rate, or a carrier
voltage which is continuously modulated at a de
sired frequency rate. In this regard it will be
understood that the selective actuation of the
switch 33 to either of its two operating positions
determines whether the apparatus will produce a
pulse or continuously modulated carrier voltage;
that the setting of the switch 34 in one of its
intercoupled. This plate is provided with an
arcuate slot 41 which is of gradually decreasing
width from the lower end to the upper end there
of, as viewed in Fig. 3 of the drawings, and is
so formed that, regardless of 7 he position of the
rotor plate, the portion thereof in registry with
the opening 24b overlies the central portion of
the opening. More speci?cally, the two edges 41a
and 41b of the slot are eccentrically or non-con
centrically disposed with respect to the center of
rotation of the rotor plate, whereby portions of
the rotor plate adjacent both edges of the slot
overlie the opening 24b.
?ve positions determines whether the generated
carrier voltage shall be unmodulated or shall be
modulated at a particular frequency; and that
the setting of the condenser adjusting knob 35
In order to prevent stray coupling between the
two inductance elements 23 and 28, it is essential
that the portions of the rotor plate which cover
the opening 24!) be maintained in good physical
and electrical contact with the adjacent portion
of the housing wall 24a. To this end, the edge
of the housing wall which de?nes the opening 24b
is provided with a struck out ?anged portion 240
which extends toward the adjacent surface of
the rotor plate 29 and may be formed by a stamp
ing operation or the equivalent. The inner sur
determines the particular carrier frequency at
which the signal voltage shall be generated. It
will also be apparent from the preceding explana
tion that the setting of the rotor plate adjusting
knob 4| will determine the extent of coupling
between the output inductance element 23 and the
pickup inductance element 28 and, hence, ‘the
energy j~transfer ibetween" the = output side‘of :the
"maximum voltage :is developedbetwee'n the ~;ter'
generator :and the" utilization - circuit: ‘1
After the » above adjustments have ‘ been amade,
‘mi'nals “of therinductance "element '~28'.=1“»As {the
rotor plate is adjusted to‘positions intermediate
the-switch 32' may ‘be’. actuated to its “,on’r’" position
.rent 'to the‘ tubes provided in the *three stages
the‘ two described extreme‘positio'n's,ftheI coupling ,
betweenithertwo inductance elementsv 23'iand'2'8
isv ‘correspondingly ; varied vbetween" the‘ minimum
10,4 land I2, thereby to initiate the operation of
and maximum values to‘correspondin'gly change
thegenerator; When“ cathode heating-:currentis
the voltage ‘produced across the 'terminalsvofl‘the
supplied to; the tube l3,vv the oscillator 12 *ge'n
erates an oscillatory voltagewat-ithe particular
radio frequency-determined'by‘the setting of the 10
;tuning @condenser, ‘[9; In- this regard ‘it will be
noted thatthe carrieror‘radio frequencycurrent
pickup inductance element 28.‘
While it will be 'understood'th'at therstru‘ctural
speci?cations may :vary according to ‘the design
of a particularapplication for the '“a'ttenuatih'g
device, the ' following - speci?cations'ifor the ‘illus
.traversing'the space-current path of the tube 13
trateddevice vare given by ‘way of example as be;
also-traverses thecondenser "2| ' and the lower
:se'ctionaMa of the inductance‘ element M.- This 15 ing satisfactory when usedfinwconjunctionl-with
a signal generator havingi'anf‘output carrier-‘fire
section‘ of the rinductanceelement‘ ‘is- inductively
variable between 150 Land 250 imeg‘acycle‘s
coupled to the upper section ‘14b thereof so'that
‘which 'may- "be continuously or- pulse ‘modulated
radio ,frequency {energy may :be" transferred-:fr'om
"at ‘a lfr'equencyrrange extending ‘from 100 cycles
the output circuit 'to .the-finput- ‘circuit Yet 'the
tube~l3 :for the *purpose‘rof' sustaining the gen 20 to‘a maximum value-‘of 100 kilocyclesr "
eratediosci-llatory'voltage.‘ ‘The modulating volt
Output inductance element 23:
*age'developed through ‘operation of the multi
quencyiampli?er 1| l and is i-util-izedifor plate cir
cuitmodulation of the icarrier'frequency voltage
developedvbetweenrthe anode and cathode of the
ductance element 14, ‘i. e.>that portion of the in
ductance element I4 which is includedin the out
put circuit of the tube l3. A portion of this mod
ulated voltage, i. e. that appearing across the
section I40 of the inductance element I4, is im
pressed directly across the terminals of the out
put inductance element ‘23'. Due to the mutual
inductive ‘coupling which exists between the two
inductance'elements 23_and 28 through the ‘open
ing 2%, a voltage isjdevelcped' betweenjthe ter
minal ends’of the pickup inductance‘ element 28.
This'voltage is impressed upon the utilization cir
cuit through ‘the conductors 26a and 21a and the
inner contacts of the connectors‘ 25d and 25b
to which these conductors are respectively con
nected; _ The magnitude of‘ this ‘ voltage and,
hence, the extent of energy transfer between the /
two inductance elements 231. and '28“is'v of course
______ __; _________________ __
- wire having an inside diameter"
of a _____ __r____r _______________ __
Diameter of the opening 24b_?__-__»____~‘_.’ .875"
30 Distance between inductance elements .
Minimum width of slot EL‘____ __‘__~____. .0937"
Angle covered by slot 4‘l__._r_ ____ __'___v_lAp. 19'5"’
Angle voi rotation-of plate 29;.“_;=____-Ap.i180°
‘Referring now‘ more particularly “to ‘Fig. 7' '6 "of
the ‘drawings, ‘the attenuation curve there illusi
trate'd-is an exact reproduction‘of. ia‘curve ob‘;
tained' byxtesting‘ a‘working ‘embodiment Yofthe
invention characterized by‘the physical 'andstruc
.tural dimensions outlined above. ‘' In‘this curve,
the 'signal' attenuation’ -‘ from the available Tm'a'xii
mum value as measured ‘in decibels ‘is plotted "as a‘
function of ‘the “position ' of the‘ rotor plate '29.
From an examination'pf this curve it will be ap~ ‘
parent that when the rotor plate occupies ‘the
position in which the opening ‘24b is substantially
closed such that minimum coupling between the
two inductance elementsv is' obtained,’ the ‘attend;
ation of signalenergy transfer is at a maximum
which is of‘lthe'order of 58 decibels; As the-‘rotor
plate is rotated‘to increase the area of the open‘:
ing through which the two’ elements
are ‘coupled, .
the attenuation ofgenergy'ltransfer'is sharply re!
duced'. Asthe'rotor platejsrotat'e'd‘ to ‘a’ position
' ‘in which the maximurn'l'coupling area ‘is'provided,
determined by the amount ofinductive coupling
the attenuation is substantiallynegligible. From
therebetween, and this coupling ‘is in turn deter
mined by the setting of the rotor plate 29.1 More
spe‘ci?callyr,‘-if the rotor plate is's'o adjusted that
‘the'narrow end portion 41c‘ of the slot 41 overlies
siderati-on of the ‘con?guration‘of‘the‘slot'47,‘it
will be understoodv that by ‘suitably?sh'aping- ‘this’
the‘ opening 24!), ‘whereby the effective coupling
.area between-the’ two ~coils- 23 and>28 is small,
only‘, a ‘negligible amount of coupling isv present
betweenvthe two coils 23 and 28 and, accordingly,
the voltage developed between‘ the terminals of
the element ‘28 is of a low order of magnitude.
On the other hand, if the rotor plate 29 is ‘sol
adjusted thatthe'portion of the slot 41 of maxi
mum" width overlies the opening 24b, a substan
tial“ coupling - area “between the two inductance
merits 2s and 2a-",________ __'_____>_‘_, .3125"
Mean radius of ‘slot 67-; _________ __>___,. 1.25’?
Maximum width of slot '4i_'____\__‘____‘_. 1 525""
‘understood, therefore, that,‘ depending “upon the
veloped across the lower sectionvMa of the in
Pickup inductance element 28: ‘
A single loop of No.14 copper ‘tinned
ioscillatorltube-il 2; ' This'modul‘ating Voltage may
“either be utilized to continuously modulate ' the
setting of the switchl33, a-pulse or continuously
modulated radio frequency carrierpvoltage is de
wire having "an inside diameter
vibrator 4!} ‘is ampli?ed ‘through > ‘the - audio "fre—
voltage- appearing across‘ the inductance ‘element
section I'4a_~ata ‘frequency determined by the set
ting of the rotary switch 34, orto ‘pulse modulate
the radio -frequency yoltage. developed by the os
cillator l2 at-a -~particular frequency. determined
by the :settingof ‘the? switch ~34’, The types-of
“modulation obtained depends upon the particular
.positionoccupied- byv theswitch 33.: vIt willhe
A single loop of Nopl‘lcopp‘er tinned ‘
an examination of this curve and 'a further'con;
slot, any desired characteristic attenuation vcurve
may be obtained. Thus, by appropriate design'o‘f
the slot ‘con?guration, there maybe obtained an
attenuation curve which is substantially linear
from the point of maximum attenuation to'ithe
point of minimum attenuation.
From the foregoing explanation, it will vbe un-'
derstood that the described "attenuating ' device
is particularly applicable for use-in ‘governing the
signalenergy transfer'betweenith’ei output side of
a signal generator or other source‘ of 'high‘frel
quency current and ‘an ‘associated pick-up circuit;
‘elements 23 and 28 is provided,- T such ' that! the
75 It will ‘ also be‘ understood- that the device "is; "of
rugged structure and may be constructed to pro
‘vide an extremely wide range of attenuation.
Moreover, it is thoroughly reliable in operation
and may easily be calibrated ‘to provide a visual
indication of the extent of attenuation for any an
“setting of the rotor plate 29 embodied therein.
While one embodiment of the invention has
been disclosed, it will be understood that various
modi?cations may be made therein, which are 10
within the true spirit and scope of the invention.
I claim:
said housing and provided with a control panel
spaced apart from said one wall of said housing,
terminal connectors supported upon said panel,
shielded conductor sections extending between
said wal1 and said panel from said connectors to
points in proximity to said inductance element,
a pickup inductance element connected between
the adjacent ends of said conductor sections and
disposed between said one wall and said panel in
proximity to said output inductance element, said
one wall being provided with an opening therein
through which said inductance elements are mu
In combination with a signal generator which
tually coupled, and means for variably closing said
opening, thereby to vary the coupling between
includes circuit elements disposed within a con
ductive housing and is provided with an output 15 said inductance elements.
inductance element disposed within said housing
adjacent one wall thereof, a chassis supporting
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