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Патент USA US2404542

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July 23, 1946-
Original Filed Nov. 4, 1940
10 Sheets-Sheet 2
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July 23, 1946,;-
10 Sheets-Sheet 4
Qriginal Filed Nov‘. 4, 1940
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DA V/D H. .S‘L 0A N.
July 23, 1946.
Original Filed Nov. 4, 1940
10 Sheets-Sheet 5
July 23, 1946.
Original Filed Nqv. 4, 1940
10 Sheets-Sheet 6
July 23, 1945-
Original Filed Nov. 4, 1940
10 Sheets-Sheet 7
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July 23, 1946.
Original Filed Nov. 4, 1940
10 Sheets-Sheet 8
July‘ 23, 1946.
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Original Filed Nov. 4, 1940
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J34 '
DA v10 H. SLOAN.
Patented July 23, 1946',
' 1,404,542
I’ '
' a oer-flog
, David H.‘ Sloan, Berkeley, Calif" aasignor to
Research Corporation, New York, N. Y., a cor
poration of New York
Original application November 4, 1940, Serial lilo.
864,284. Divided and this application June 9,
1941, Serial No. 897,235
21 Claims; (Cl. 178-44)
of temperature or ordinary shock. so that the fre
quency to which the device as a whole is tuned
This invention relates to electronic tubes, and '
particularly to tubes adapted for the production
will not be affected by relative changes of posi
tion; ?fth, minimum undesired or "incidental"
and modulation of ultra-high frequency oscilla
tions, 1. e., oscillations of frequencies of the order
of 1,000 megacycles. This application is a divi
sion of my prior application Serial No. 364,284,
filed November 4. 1940.
The progress of electronic and radio develop
ment since the inception of the art has been‘
marked by two steady advances. One of these
advances has been toward higher power, the
other toward higher frequencies. The latter line
radiation from the various elements of the tube
and its auxiliaries; sixth, 9, minimum of insulat
ing material subjected to high-frequency ?elds.
To these may be added the secondary require
ments of demountability for replacement of ?la
ments, facility in water cooling and avoidance of
hot spots, and ease of tuning.
From the conventional approach these require
ments are incompatible to a large degree. _A high
of advancement has been, to a certain extent at
degree of control requires close spacing of cath
ode and grid, which leads to high interelectrode
least, incompatible with the first, since with in
creasing frequency the effect of interelectrode
capacity has become greater and more trouble
capacity. Rigid structure ordinarily means mas
sive structure, which again leads to high inter
some. Nevertheless, up to the last few years, the
electrode capacity. Water cooling systems tend
di?iculties have been met by a steady evolutionary
to form effective antennae, leading to large stray
process consisting in large degree of refinement
power radiation. The broad purpose of my in
in detail, which has enabled the vacuum tube art 20
to keep pace with the increasingly rigid demands
of the manufacturers and operators of transmit
ting and receiving apparatus.
The attempt within recent years to carry the
useful spectrum into the range of wavelengths in 25
the range of a meter and less has involved dim
culties of a new order of magnitude. For one
vention is therefore to reconcile these and other
apparent incompatibles.
Pursuant to this generalpurpose, among the
objects of this invention are: to provide a tube
which is capable of producing many kilowatts of
power at extremely high frequencies; to produce
a high frequency generator of great frequency
stability; to produce a high frequency ampli?er
and oscillator tube of relatively high e?lciency,
and particularly to produce such a tube wherein
thing, the frequencies involved are so high that
the transit time of an electron stream across the
interelectrode spaces of the tubes becomes an 30 the losses due to undesired radiation from the
appreciable fraction of a cycle., For another,
tube itself are reduced to negligible proportions;
even with connecting leads reduced to minimum
to produce a high frequency oscillator and am
lengths, their inductance has been su?icient so
pli?er which may be tuned to operate at any.
that the capacities required in tuning them to the
desired frequency throughout a reasonably‘ wide
desired frequencies are small in comparison with 35 range; to provide a high frequency oscillator and
the interelectrode capacities in conventional tube
ampli?er which may be constructed with the high
structures and these capacities have therefore
degree of accuracy required to meet the close tol
become not merely a nuisance, limiting the effi
erances demanded by the frequency of operation
ciency of operation, but frequently an absolute
bar to such operation; so much so, in fact, that 40 and maintain those tolerances under the
changes of temperature produced by such opera
it has been only with tubes of very small size and
to provide an electronic tube of the char
consequent small power output that operation
acter described which may be fully ?uid cooled
has been obtainable at all. _
and wherein the cooling system does not‘ intro
There therefore exists at the present time a
need for a tube which will meet the severe re
45 duce material parasitic radiation of radio-fre
quirements of producing large power outputs by
generation or ampli?cation at extremely high fre
quency power; to provide. a high power oscillator
structure whose capacity and inductance rela- ‘
and ampli?er tube which is readily demountable
for replacement of ?laments; to provide means of
density-modulating an electron stream at ultra
high frequencies, in order to produce ‘extremely
short bursts of electron emission occurring at
peaks of the oscillation and of substantially uni
tionships- are so proportioned that they may be
tuned to the high operating frequencies desired; i
third, a structure lending itself to circuits of low
relative radio-frequency resistance of high im
pedance, so that excessive energy will not be
ciency; to provide a type of structure for high
frequency electronic tubes which is of great ?ex
ibility, and ‘which will, because of such’ ?exibility,
quencies. ' These requirements are ?rst, a cath
ode-grid structure which will effectively modulate
an electron stream without the application of ex
cessive control voltages; second, a cathode-grid
required to swing them through the necessary
range of control voltages; fourth, ?xed relation
ship between the various elements, irrespective
form velocity, whereby the conversion of energy '
into high frequency power occurs at high elli
permit the construction'of tubes exactly adapted
to a large variety of powers and services; to pro
vide a novel and effective method of tuning appa
_ 2,404,049
ratus of the character described; and to provide
a type of electrode support for high frequency
them reaching the cathode. from which emis
electronic devices which is-massive and rugged. _
sion is therefore normally suppressed. A few
. volts relative change in potential of the cathode.
and which, attlie same time. does not introduce
interelectrode' capacities which either severely 5 "as referred to either accelerator or control grid,
results in some of the lines of force from the
limit the frequencies upon which‘ the device is op
accelerator terminating in the cathode_surface.
er'ative or the power which may be developed at
such frequencies.
which is accordingly subjected to an extremely
powerful ?eld causing very large emission to the
My invention possesses numerous other objects
and features of advantage, some ‘of which, to‘- 10 anode. The result is what may be termed an
"explosive" type of emission. giving electron
gether with the foregoing. will ,be set forth in the
bursts of high density for very short periods at
following description of speci?c apparatus em
the ‘peaks of the cycles. It will be evident that
bodying and utilizing my novel method. It is
this structure results in a relatively high capacity
therefore to be understood that my method is ap
plicable to other apparatus, and that 1 do not 15 as between cathode and grid. but the tuned
transmission line support enables this capacity
limit myself in any way- to the apparatus of the
to be eii'ectively'resonated with an inductance
present application, as I may adopt various other‘
apparatus embodiments utilizing the method.
as small as may be desired and still form a
sharply tuned, high Q circuit whose high resonant
within the scope of the appended claims.
The tube of my invention involves two basic 2o input impedance may appear as resistive, capac
itive or inductive. as the conditions of operation
concepts. The ?rst of these comprises forming
may require.
electrode supports of sturdy coaxial metallic
Referring to the drawings:
cylinders which constitute a radio-frequency
Fig. l is a longitudinal section through a
a plurality of quarter wavelength electrical links, 25 high-frequency oscillator tube embodying my in
vention. the particular tube illustrated employ
with impedance irregularities at or near cer
ing a radial arrangement of ?laments and grids. '
tain of the quarter-wave points, the electrodes‘
Fig. 2 is a transverse section of the tube of
themselves forming a portion of these transmis
Fig. 1, showing the multiple coaxial grid-?la
sion lines as considered electrically. Means are
preferably provided for varying the position of 30 ment supports. and water connections for cooling
the ?lament mounting, the plane of section being
the impedance irregularities to provide exact
on the line 2—2 of Fig. 1.
tuning, but this is not essential since. as will
Fig. 3 is a transverse section through the
hereafter be shown. by a proper combination of
anode structure of the tube, the plane of section
the characteristic impedances of the quarter
wave sections and their terminating impedances, 35 being indicated by the line 3-3 of Fig. 1.
Fig. 4 is an enlarged detailed view illustrating
it is possible to make the radio-frequency im~
water-cooling connections from the exterior of
pedance of the supports as viewed from the elec~
the tube to the ?lament mounting.
trodes themselves extremely high, so that the
Fig. 5 is a schematic sectional view through
overall effect is almost as though the electrode ‘
capacities together with the inductances required 40 ?laments, control grid. accelerating grid, boun
dary grid, and anode of the tube.
to resonate them were supported freely in the
Fig. 6 is a sectional view through the grid sup
space within an unbroken metallic shield. This
‘ - transmission line of at least‘ one and
‘ latter feature is secured by providing multiple
port line, showing the ‘radio-frequency by-pass
1coaxial line sections forming branch paths of
between accelerating and boundary grids and the
‘greatly different impedance, -' certain of these 45 tuning mechanism for isolating the control grid
‘paths acting as'by-passes of negligible imped
and water cooling the same. '
3ance at points where it is necessary that some
jcirculating currents should flow, although D. C.
insulation must be maintained, while at the same
Fig. 7 is an enlarged detail showing the
method of insulating certain of the supporting
, rings upon which the coaxial electrode elements
time maintaining the high impedance desired 50 are carried.
‘in other paths which would otherwise lead to
Fig. 8 is a section taken at right angles to the
radiation. By placing these by-pass sections at
view of Fig.1, and showing the anode-support
ing, cooling, and tuning system.
lcurrent nodes. the PR losses therein may be
‘made too small to need consideration.
Fig. 9 is a perspective view of the accelerator
‘ The'second fundamental concept comprises 55 grid.
mounting on the ends of such supports, prefer
‘ably in biaxially symmertical con?guration, one
or a plurality of cathode-grid combinations
which act, as before stated, as the termini of
Fig. 10 is an elevation of the control-grid
' structure.
Fig. 11 is a sectional view, taken on the plane
between the ?lament and grid structures, and
the transmission lines formed by the supports; 60 showing in detail the ?lament support. _
mounting the grid opposed to an anode or other
accelerating electrode in such manner as to pro
Fig. 12 is a fragmentary axial section taken on
the line i2—i 2 of Fig. 11.
duce an electrostatic ?eld between grid and ac
Fig. 13 is an elevation of the active face of the
celerator which comprises lines of force very
sharply curved in the immediate neighborhood 65
Fig. 14 is a fragmentary section of the anode,
of the grid; and mounting the cathode in the'
the plane of section being indicated by the line
region of sharpest curvature. One of the best
i4-i4' in the preceding ?gure.
ways of obtaining such a structure is to form
Fig. 15 is an elevation of the boundary grid.
the grid of pairs of cylindrical surfaces whose
is a sectional View ‘taken on the line
axes are parallel to the plane of the anode, and 70
i6_i6 of Fig. 15, and showing a portion of the
to make the cathode as a ?lament or strip having
anode in elevation.
a‘ ?at or slightly concave face lying between the
Fig. 17 is an elevation of one of the ?laments.
cylindrical surfaces 01' the grid. This results in
Fig. 18 shows a modi?ed form of coaxial line
the lines of force from accelerator or anode nor:
mally terminating in the grid structure, none of 75. structure for grid-?lament support in a tube gen
erally similar to Fig. 1, but adapted for use either
of steel, and the tube l-also of seamless steel’
as an ampli?er or an oscillator with inductive
tubing, while the cylinder 2 may be either chro
mium or copper plated steel or'solid copper, with
Figs. 19.20. and 21 are'sectional views throush the tube of Fig. 18, taken on the lines numbered
in accordance with the ?gures.
Fig. 22 is a longitudinal section through a tube.
‘built in accordance with this invention but where
in a cylindrical, rather than a radial ?lament
grid and anode arrangement-is used.
copper preferred. since it forms a portion of a
resonating circuit. Carrying on from the flange
1 is a glass or "Pyrex" cylinder I‘ which abuts a
terminal flange l0.
' a whole isfully demountable.
The ends of the
tubes contact the ?anges with smooth machine
?ts. The joints thus formed are sealed by apply
ing thereto ordinary wide elastic bands as indi-v
cated by the reference characters ll, these bands
Figs. 23, 24,’ and 25 are transverse sections
through the tube of Fig. 22. taken on the linesin
dicated by the respective numerals.
As has been mentioned already, the device as
Figs. 28 and 27 are detailed views indicating the
tuning mechanism for the tube of Fig. 22.
being smeared before application with a small
Fig. 28 is a longitudinal section on a larger 15 amount of vacuum line stop-cock grease.
It may be pointed out at this time that all or
the structure thus far described with the excep
tion of the terminal ?ange III is at D. C. ground
Fig. 29 is a transverse section through the sup
potential, and as will later be shown in detail
porting columns of the tube of Fig. 22, showing
that the entire exterior structure is substantially
the construction of the centering mechanism, the 20 at radio-frequency ground. This means that the
plane of section being indicated by the line 28-48
insulating section formed by the cylinder 8 is not
of Fig. 28.
' '
subjected to R. F. ?elds. It also renders easy the
Fig. 30 is a sectional view taken on the line
support of the device by any desired external
"-30 of Fig. 22.
means. Part of such support may be the connec
Fig. 31 is a fragmentary section taken on the
tion to the pump, which is by a pipe l2 of rela
line !i—8i of the preceding ?gure, showing the
tively large lumen, welded or otherwise secured
passage of the cooling pipe past the anode and
into the bottom of the anode housing 2. This pipe '
between the two sections of the ?lament support.
is not shown in Fig. 1, but is clearly visible at the
scale through the ?lament support or the tube of
. Fl g. 22.
Fig. 32 is an impedance diagram for an open
ended, half wavelength section of transmission 30
In the ensuing speci?cation the invention will
?rst be described in its various aspects as applied
to an oscillator tube oi’ moderate power (1. e., ap
bottom of Fig. 8.
The various elements which contribute to the
electronic action of the tube are mounted within
the envelope thus formed on columnar supports
each of which has transmission line character
istics designed to meet its particular function.
These elements are shown in schematic arrange
proximately 10 kw. peak output at 20 to 40 centi
meters wavelength). Following this there will
ment in Fig. 5, and comprise an anode it, a
be described two modi?cations illustrating respec
boundary grid 4, an accelerating grid IS, a con
tively the application of the principles of my in
trol grid l6, and a ?lamentary cathode i'l.
vention to a similar tube adapted for ampli?ca
Fig. 5 is drawn to a greatly enlarged scale and
tion or for generation of oscillations by inductive 40 shows a fragmentary section of the elements co,
feed-back, and to a somewhat higher output de
operating with a single filamentary cathode. In
vice showing the principles as applied to a tube
the tube here shown six such cathodes are used.
constructed with cylindrical rather than radial
and the portions shown of the other elements
arrangement of electrodes.
are repeated for each cathode.
The tube shown in longitudinal section in'Fig.
l is of the demountable, constantly pumped type,
as in fact, are all of those herein described, al
though the principles involved are not limited for
One advantage
of the type of structure here shown is that the
ability of the tube to supply power output varies
almost directly as the number of ?laments used,
and that the changes required to add additional
use in such tubes. From the structural point of 50 ?laments are relatively minor. Tubes have been
view the tube comprises a series of ?anges con
designed conforming substantially to the struc
nected by sections of tubing and held together in
ture here shown with as high as twenty-four
compression. From a practical point of view it
?laments, each with its attendant grid-anode
is advantageous to have the ?anges pierced for
structure, but since each of these assemblies is
andlield by circumferential bolts to hold the parts 55 merely the duplicate of the others as far as per
?rmly in position when the tube is not under vac
formance is concerned, it is suiilcient for the
uum, but when in use the external air pressure
present to consider one only.
tends to hold the entire device together, and the
Considering, therefore, the portion of the ele
tube has actually been operated without the re
ments shown in Fig. 5, the anode i3, preferably
taining bolts; these have therefore been omitted
in the drawings since they add a further com
plexity of detail to an already complex structure.
Considering for the moment, therefore, only
the external structure which forms the housing
and which supports the remainder of the equip-.
ment, the tube comprises an anode housing flange
l which is grooved to receive tightly the end of a
tubular anode housing 2. This housing ?ts an in
ternal recess or counterbore in an annular grid
?ange 3, clamping a boundary grid 4 between the
housing tube 2 and the ?ange. A rabbet on the
outer periphery of the ?ange 3 receives one end
made of high conductivity oxygen-free copper,
is operated at the maximum potential of the sys
tem, say 10 to 50 thousand volts positive. It is
provided with a V-shaped groove 20 with its axis
parallelto the axis of the ?lament. Next, pro
ceeding toward the ?lament, is the boundary
grid 4, which is also preferably made of oxygen
free copper. This is provided with an aperture
surrounded by a collar 2| in accurate alinement
with the groove 20 in the anode. Next in line is
70 the accelerator grid IS, with a slot 22 which is
of a main support cylinder 5, whose other end
terminates in another annular ?ange ‘I. All of
the parts thus far mentioned are of metal, and
I have found it convenient to make the flanges 75
somewhat narrower than the opening in the .
boundary grid, and which isoperated at a poten
tial above the cathode of from 5 to 20 thousand
volts. All potentials mentioned are illustrative
and relative only, since the actual values used
will depend upon the size, power output and ‘op
erating frequency'of the device. Furthermore, -
modi?cations in design are possible whereby the
functions of certain of the grids are combined.
other electrodes are operated at ground potential,
etc. , Such modifications will be considered later;
the purpose here is to show the application of
the principles of my invention to the present tube.
‘ The most important portion of the combination
is the arrangement of the cathode-grid struc-‘
ture. The important features here are first, that
i , the control-grid elements comprise parallel cylin
drical surfaces, curved as they are presented to
the ?lament.
In the present case they are rods
or wires. but they could be cylindrical surfaces
formed as the edges of a_ slot in a ?at plate with
out affecting their performance.
Between these '
surfaces, and slightly back of the plane of their
centers of curvature, lies the ?lament, which has
a. ?at or preferably a slightly hollow ground face.
presented to the anode. It is convenient to op
erate the ?lament at ground potential (disregard
The important point is that because the region
is so shallow all of the electrons emitted do get
through it before the cycle hasv advanced too far '
and, having traversed it. fall into the region of
high potential gradient where, acceleration to
ward the anode is very great; space charge effect
is of no further moment, and they receive so
large a portion of their final velocity that their
differences of velocity .in the initial region are im
It should be realized that while space-charge
effect prevents some emission and decreases the
acceleration of electrons emitted, it will not drive
those which have been emitted back to the
cathode nor prevent-their reaching the anode. It
follows that the space-charge region may be con
sldered as a reservoir for emitted electrons. With
conventional grid-cathode structures it is rela~
tively deep, so that, at the frequencies and powers
at which this tube is intended to operate, transit
therethrough occupies a major portion of the
cycle, and'with the varying velocities obtaining
while in this region the electrons straggle
to operate the grid it at 200 to 500 volts negative. ‘ , through to reach the anode in such varying phases
that the density modulation of the stream is al
It will be seen that at the orders of voltages
most if not entirely lost.
given the major ?elds are from the accelerator
With the arrangement of my invention, how
grid i5 to the control grid. As is wellknown,
the lines of force constituting such a ?eld termi
ever, the space-charge region is so shallow that
nate at' right angles to the surfaces of the field
even the stragglers among the emitted electrons
ing for the moment the slight voltage drop along
the ?lament) and, for the powers here considered,
1 de?ning electrodes. It follows that in theregion
traverse it in less than a quarter cycle and in
‘ adjacent the-cathode the lines of force emerge ,
stead of the density modulation of the electrons
being lost they reach the anode in bursts of such
‘ from the grid wires in the general direction of
l the cathode and then curve very sharply toward
1 the anode in a‘ direction nearly at right angles _
power and suddenness and with such close
There is also
velocity grouping that I have termed cathode
grid combinations of this type “explosive.” The
1 a fairly strong ?eld between the control grid and
v the cathode itself, which is superimposed locally
voir constituted by the space-charge region as
i to their direction of emergence.
object of the design is to make the electron reser
1 upon the ?eld between the control grid and ac
l celerator grid, and is directed toward, instead of
. away from the cathode.
shallow as possible, and in practice the ideal can
be so. far realized as to permit density modula
tion of electron streams at frequencies in the
range of 1,500 megacycles, where in the past it
As a result of the inter
action of these two ?elds none of the lines of
force from the accelerator-grid normally termi
; nate upon the surface of the cathode.
‘ has therefore no tendency to leave the latter, ,
1 since the space adjacent it is nearly neutral, with
such weak ?eld as exists therein directed toward
a‘ the cathode.
As is the case with any grid-controlled tube
Ioperated through cut-off, when the grid swings
positive some of the lines of force from the ac- '
Icelerator-grid which formerly terminated on the
1control grid now terminate on the cathode, and
$3.5 the cycle progresses the cathode-contro1 grid
l?eld weakens or even reverses, permitting emis
sion toward the anode, and a. space charge builds
‘up in the region immediately in front of the oath.
‘ode face which has the usual effect of limiting
emission. The distinguishing feature here is that
the region where the ?eld is weak enough to per
mit such space charge effect is very shallow, .so
that even with the low velocities imparted to them
by such relatively weak ?eld the electrons can
‘and do traverse it in a reasonably small fractio'
of a cycle.
‘ The biasing potential between cathode and grid
is so adjusted that emission can occur only for an
. instant at the cycle peaks, and cut-oil‘ may occur
even before the ?rst electrons emitted have trav
. ersed the space charge region. Furthermore,
while in this region there is a maximum di?erence
of velocity as between electrons, both by reason
of differing initial velocities of emission and,
more important, by reason of differing accelera
tion due both to phase of emission and ?eld
strength at various parts of the cathode surface.
has been necessary to use velocity modulation,
involving larger and more complicated structures,
to get reasonably effective results, even in smaller
sizes and at much lower powers than those here
When the tube here shown is used as an oscil
lator in the manner now to be described, the
various potentials are 50 arranged and propor
tioned that the transit time of the burst of elec
trons is substantially one-half cycle. The anode
i3 is in a tuned circuit, as is also the grid IS.
The condition of oscillation then is that the
potentials of the anode and the grid swing in the
same sense, ‘50 that the grid reaches its peak of
positive potential at the same instant as does the
One of the results of the conformation of the
electrostatic ?elds is a strong focusing action
upon the electron bursts, and these bursts ac
cordingly fall upon an extremely limited portion
of the anode surface, substantially none reaching
either of the intermediate grids. The anode area
upon which the electron bursts impinge is that
included in the \_/-shaped slot 20. The reason for
, this arrangement is to spread the area of impact
and so increase the size and decrease the in
‘ tensity of maximum local heating, while increas
‘ ing the cross-sectional area of thermal conduc
tivity by which cooling occurs, and also to in
sure that secondary electrons are not projected
into regions of high ?eld intensity which would
accelerate them so that they, in turn. would cause
serious heating effects.
It has already been stated that the transit time
'of the electron burst is one-half cycle of oscilla
tion, and it follows that immediately after the ,
electron burst has occurred the anode has started.
to swing negative.
The electrons accordingly
reach their maximum velocity at or about the
plane of the accelerator grid-ideally. Just as they
‘pass the effective plane of the boundary grid 4.
As the anode continues to swing negative they en
counter a decelerating ?eld, either in an absolute
sense or, if still being accelerated by the D.-C.
?eld, from the anode at least in comparison to
the acceleration of the D.-C. ?eld alone. In pass
ing through(this decelerating ?eld the electrons
are delivering energy to the anode circuit, and
they are traveling at minimum relative velocity 15
when they enter the slot 20. This slot acts in'
some degree as a Faraday space, and the elec
trons suffer little change in velocity or energy as
tubing 32 surfaced to a sliding ?t on the column
25 and shouldered. at each end to receive discs
33 and 34 between which a short section of tubing
35 is clamped. The column 25 is provided in this
region with a longitudinal slot‘ for the passage of
a screw 31 which engages a piece of tubing 33
sliding within the column. The\tubing 33 termi- ‘
nates in an annular block 40; and an adjusting
rod 4| is threaded into one side of the block and
passes to the exterior of the tube through a gland
box 42 and a “Wilson seal” 43. It is apparent
that the position of the slider may be adjusted by
sliding the rod 4|,
A word as to the Wilson seal may here be in
order, and in this connection attention is drawn
to the showing at the lower right of Fig. 8. The
seal proper consists of a normally ?at washer 45
of synthetic or natural rubber, which is forced
' against a conical seat 41 by the internally conical
done and their transit time effectively over as 20 edges of a gland 43. When the washer is un
they pass through it. ' Therefore their work is
soon as they have entered it.
Since the acceleration of the entire burst of
, electrons takes‘ place with substantial uniformity
stressed the aperture therethrough is slightly too
small for the rod 50'which it is desired to seal.
The seal is lubricated with a ‘small quantity of
vacuum stop-cock grease. Such a seal is vacuum
they retain their close grouping at the time of
‘impact, and since the impact occurs when the 25 tight‘ under conditions where other known types
of packing ‘would leak badly, since the di?erential
electrons constituting the burst have suffered
pressure on the washer serves to make it hug the
maximum deceleration there is a minimum of
central rod more tightly and it remains tight
energy wasted as heat and the oscillator conse
whether the rod be subjected to rotary or slid
quently operates at relatively high e?iciency.
For operation in the manner described the 30 ing motion in either direction.
Returning to the general tube structure, the
desiderata are that the control grid l6 and ?la
second and lower slider 5| is essentially similar
ment 11- should be e?fectively isolated from' each
in construtcion to that just described, except
other both as regards D.-C. and radio-frequency
that its actuating rod 52 is mounted externally of
potentials, and should have an effective ‘capacity
sufficiently low so that it may be tuned to the 35 the column 25 through the gland'box 42 and
Wilson seal 53. '
desired operating frequency, or, in other terms,
The'slider 5| makes a close ‘sliding ?t within
.it must be capable of being connected in circuit
a cylindrical conductor 54‘ mounted in the ?ange
with an inductance sufliciently small to tune to
l0 accurately concentric with the column 25 and
that frequency. The accelerator grid [5 must be
insulated from the other elements to maintain 40 maintained in this concentric relation both by
the slider 5| itself and by an auxiliary diaphragm
its D.-C. voltage, but should be e?ectively
or spacer'55. The tubing 54 does not extend the
grounded as regards radio-frequency potentials,
full length of the central column, but terminates
The boundary grid 4 should also be grounded to
a distance above the ?ange ‘I which is somewhere
radio-frequency and for convenience in operation
and safety’s sake should preferably also be 45 in the neighborhood of one-eighth of a wave
length at the mean frequency for which the tube
grounded as regards D.-C. potential, as it is elec
is designed.
trically continuous with the envelope. The anode
Accurately coaxial with the column 25 and its
should be free as regards both A.-C. and D.-C.
surrounding conductor 5| is a third conducting
The various mounting and auxiliary means 50 cylinder 51, mounted on the ?ange ‘I and extend
ing below it for approximately one-eighth wave
next to be described are designed to meet the
length, so that the two conductors 54 and 51
desiderata as fully as possible. In this descrip
overlap by a distance approximately equal to one
tion terms such as “above” or “below”_ are used
quarter wavelength of the average operating fre
to. indicate position as shown‘ in Fig. 1. They
have no other signi?cance, as the device may be 55 guency of the device, wavelengths in this sense
'being used-to mean the wavelength of the fre
operated in any position.
quency transmitted along the two tubes as a co
Starting at the bottom of Fig. 1, with the ?ange
axial transmission line. There is no metallic con
III, a high conductivity column or pipe 25 extends
tact between the two conductors 54 and 51. and
a major portion of the length of the entire de
vice to the plane of the ?ange 3 and the boundary 60 they are separated by vacuum so that dielectric
grid 4. This column is brazed or otherwise per
' manently secured into the ?ange l0 so as to be
accurately concentric with. the remainder of the
- tube structure and, of course, to be vacuum tight.
At its upper end it is threaded to receive a grid:
support ring 21, which is clamped between locking
nuts 29 and 30, and an additional locking screw
3| (Fig. 10) is also provided for further security,
The pairs of parallel grid wires l5 project from
the ring 21 parallel to its radii, six pairsot grid
wires being provided in the present design, the
pairs being equidistantly spaced around the pe
loss does not occur in the space between them.
Column 5l_ is brazed or otherwise secured in
the ?ange 1, is made of highly conducting mate
rial (preferably oxygen-free copper) and is pref
erably provided with a cooling system comprising
a water pipe 60 coiled around and soldered to the
external surface of the column. The ends of this
- pipe are brought out through the ?ange ‘I at the
right of Fig. 1.
The upper end of the column 51 carries an in-1
termediate ring 6| which supports indirectly one
end of each of the ?laments H. The other ends
of these ?laments are carried by a group (here
riphery 0f the ring.
six) of pipes.62 mounted in the annular inter
Two sliders aremountedon the column 25.
The upper slider 23 comprises a short section of 75 space between the column 51 and the outer shell
6. .The lower ends of the pipes 62 are mounted
in a ring 63 which is bolted to and insulated
these points, with a‘ consequent greater liberation
of heat which compensates for the heat conduc
tion to the clamping means and results in sub
from the ?ange 1 as is shown in Figs. 2 and 7.
The ring 63 is counterbored at three equidistant
stantially constant temperature and substan
points to receive insulating beads 64 of porcelain, 5 tially constant emission over the entire effective
lava, or other ' refractory insulating material
length‘ of the ?lament. ,Being of pure tungsten,
which beads space the rings slightly from the
the ?lament retains a degree of resiliency even
?ange 1. A cap screw 66 passes in turn through a
at its emitting temperature, and this, together
clamping cap 61, a second bead 69, the ring 63
with its resilient support, prevents buckling or
and the bead 64 to clamp the ring ?rmly to the 10 change of plane of the emitting surface when in
?ange. It should .be noted that the potentials
operation and keeps the electrical constants of
which this arrangement must withstand are of
the device ?xed under such minor variations in
low frequency and ‘are only those across the ?la
operating temperature and expansion, and in—
ment, 1. e., the insulation need only be of sum
equality in these factors as between the several
‘ cient value to withstand a few volts (three at 60
?laments, as inevitably occur in practice.
cycles in the instant structure) and the insulat
Cooling for the support of the inner ends of
ing material is not subject to dielectric heating
the ?laments is accomplished by conduction
from radio-frequency ?elds.
through the support rings 14 and 6| to the col
The actual'?lament mounting can best be seen
umn 51 and thence through the cooling coil 60.
in Figs. 11 and‘12. Each ‘of the tubes 62 carries 20 Cooling for the outer supports is by circulatory
an inwardly projecting L-shaped lug 10, and the
system within the support pipes 62 themselves.
inner ends of the lugs are provided with slOts 1| ‘
A small water pipe 90 enters the side of each of
for receiving the downturned ends of the staple
the support pipes 62, and extends axially within
shaped ?laments l1, the ends being clamped into
it to a point adjacent the lug 10, so that water
place by set-screws 12. The inner ends of the 25 entering this pipe will be squirted against the in
?laments are clamped in an annular groove 13,
formed in an‘ inner mounting ring 14 which is
ner end of the lug.
From there it returns
through the pipe 62 externally of the pipe 90 to
supported on column 51 by the intermediate ring
the bottom of pipe 62, where the end 90’ of the
6| before mentioned. The actual clamping of
next pipe is connected to carry the water to the
the ?lament ends is accomplished by pairs of set 30 next ?lament support, circulation thereby occur
screws 15 bearing on small blocks 11. .
ring through each of the support pipes 62 in suc
The pipes 62 are surrounded by open-ended cy
' cession.
lindrical conductors 19, which terminate at the
The supply for this circulatory system is
level of the upper end of the lug and extend down
through a ?tting designated by the general ref
over the pipe 62 for approximately one-quarter 35 erence character 9|, comprising coaxial pipes 92
wavelength and are supported by the ring 6|.
and 03 which connect respectively to the two ends
Within the conductors 19 are inner tubular con-'
of the system. The outer of these pipes is per
ductors 80 of substantially the same length, open
manently secured to the support ring 63 (see Fig.
at their upper ends and mounted by their lower
4). The ?tting 9| passes through the ?ange 1
ends on the pipes 62 by means of conductive 40 and is insulated'therefrom by insulating bush
blocks 8|. The concentric tubes 18 and 80 are
ings 94 of steatite or other refractory between
both open ‘at the ?lament end, being notched to'
which is a compressed rubber washer 95 forming
clear the lugs10 and also being provided with
a‘. vacuum-tight seal. A connecting lug 91 for
aligned holes to permit tightening of the set
connecting one ?lament supply lead is mounted
screws 12. It will thus be seen that the only con 45 upon the ?tting ill, and the ring 63, and the cir
nection between the inner column 51 with its sup
culatory system comprising pipes 90 and 62 all
porting rings 6| and 14 and the group of ?la
constitute the conducting system for supplying
ment support tubes 62 is the ?laments themselves.
the ?lament current. The return circuit is
These are shown in Fig. 1'7, and as will be
through the column 51 and the ?ange 1, to which
' seen are relatively short and rigid. They are
a second connecting lug (not shown) is attached.
preferably of pure tungsten and have a consider 60
There are two other features comprised within
able degree of strength. It will further be seen
the ?lament-grid structure and their supporting
that the support afforded their outer ends by the
systems. The ?rst of these is a sliding plug 99
‘tubes 62 and lugs 10 is light and of small inertia
mounted in the end of the inner support column
and that the tubes 62 have relatively large resil 55 25, ‘and adjustable as to position by means of an
iency. The ?laments therefore are very unlikely
operating rod I00, and an offset extension rod
to be ruptured by shock on the device as a whole,
l0l passing through a Wilson seal I02 in the
and there is ample ?exibility to take ‘up their
gland box 42. The second is a cooling pipe I03
which extends substantially the full length of the
Each ?lament is preferably formed of round
inner column 25 and is soldered thereto adjacent
tungsten wire, one surface of which is ground 60 its upper end for better heat transfer.
?at or slightly concave. The diameter here used
We are now in a position to consider the elec
is 50 mils. The grinding is preferably performed
trical characteristics of the ?lament-grid struc
in a. jig which deforms the wire slightly in the
ture in View of the desiderata above set forth,_and
longitudinal direction, so that the ends of the 65 it
is believed appropriate to do this at this point,
?lament are around a few thousandths of an
smce the, same principles are involved in the sup
inch thinner than is the central portion. This
for the remaining elements of the device
grinding forms the ?at emitting surface of the
explanation of all will be simpli?ed if
?lament, and if done with a relatively. small
wheel whose axis is maintained parallel to the 70 these principles are in mind. The necessary sep
aration of the elements as regards D. C. or low fre
length’ of the ?lament, it gives the slight hollow
potentials have already been accounted
grinding which has already been stated to be
for. There is no metallic connection between the
advantageous. The effect of thinning the two
grid-support column 25 and the ?lament-support
ends, adjacent the point where the ?lament is
clamped, is to give a greater current density at 78 system comprising the column 51, and the sup
port pipes 62. Remaining to be accounted for
‘ 13
is the impedance relationship between the grid
From this aspect the ?rst section oithe struc- I
ture is the section including the adjusting rods
52, 4!, etc., the ?ange l0, and the section of the
‘tubular conductor 54 illustrated as below the end
of the column 51. Electrically this portion of the
structure is a single conductor, and viewed from
and ?lament members, and this is dependent upon
the impedance of the coaxial transmission line
formed by the inner and outer columns 25 and
S'Iitand the coaxial conductors associated there
its upper end constitutes an end-fed antenna.
The impedance characteristics of transmission
It is preferable that its length be of the order of
one-half wavelength at the operating frequency
lines whose lengths are of the same order of mag
nitude as the wavelengths of electrical oscilla
tions transmitted thereby are now well known,
but they are restated here for convenience in the
explanations that ‘follow. Most of them can be
of the device, in which case its effective impedance
Z2 will be in the neighborhood of 1,000 ohms.‘ If
its length be reduced to one-quarter wavelength
its e?ective input impedance will likewise be re
derived from the impedance diagram of a half
duced 'tothe neighborhood of from 50 to 100
wave line open at the output end, as shown in Fig.
32, which indicates such a line diagrammatically, 15 ohms, the quarter wavelength condition being the
least desirable in practice. This antenna is con
and shows the approximate curve of relative im
sidered as being fed by the coaxial transmission
pedance looking into any portion of the line from
line comprising the tubular conductor 54 as the
the right, resistance of the conductors themselves
inner element and the column 51 as the Outer
being assumed to approach zero. Extremely short
sections show a high capacitive reactance, which 20 element. With the spacing shown such a trans
mission line will have ai'i'characteristic' or- surge
falls to the characteristic ‘impedance of
impedance Z0 of about 10 ohms,and as has al
ready been stated the length of this section of
transmission line is approximately M4, where A
is the wavelength atthe frequency of operation.
If we consider the quarter-wave condition to be‘
ful?lled exactly the impedance looking into the
of the line at the 1A; wavelength point, and to zero
at the quarter-wave point, i. e., a quarter-wave
apen-ended line acts as a dead short. From this
point on the apparent reactance is inductive, ris
ing again to the value of
coaxial line from the grid end will be
> ‘If the antenna section of the system has an im
pedance of the order of 1,000 ohms, the charac
teristic impedance of the line being 10 ohms, the
The same diagram may be taken as represent
ing the impedance of, a shorted-end line if the .35 input impedance of the line will therefore be it:
of an ohm. This low impedance therefore be
origin be taken at the nodal or quarter-wave
comes the closing impedance of the section of line
point, which appears as a short when looking into
immediately preceding it. From one point of view
For short sections the reactance is
the line.
it acts as a radio-frequency ‘by-pass between the
small and inductive, it rises to
40 inner conductor 54 and the outer conductor 51, so
that viewed from the input end, at radio-fre
at the %7\ point and approaching in?nity at V2)‘.
quencies the cylinder 54 and outer column 51 ap
at the 1/2x point and approaches in?nity at V4.
pear as a single conductor, and form, in connec
Since this appears as an open circuit, increasing
tion with inner column 25, a single radio-fre
quency transmission line considered as fed from
the length of the line repeats the Portion of the
diagram shown at the left of the nodal point.
the grid-?lament end through a slight impedance
irregularity where the inner cylinder 54 termi
nates. Its e?ect from another point of View will
be considered later.
Stated in another manner, a quarter-wave open
line or a half-wave shorted line appears much like
a series resonant circuit, while a quarter-wave
Even if the conditions as to impedance of an
shorted line or a half-wave open line appears like 50
tenna and length of the coaxial line constituting
an anti-resonant or parallel resonant circuit.
the column 5'! and cylinder 54 are not exactly
The only other relationship necessary to the
met the result will be substantially thesame.
understanding of the present invention is that the
The antenna impedance can easily be kept above
characteristic impedance of a quarter-wave line
'is the geometric mean between its input and clos-v 55 '100 ohms, making the impedance looking ‘into
the quarter wavelength line 1 ohm. If the length
ing impedances. The short-circuit and open-cir
of the line section is not exactly oneequarter
cuit conditions are, of course, merely special cases
wave, but is still materially greater than one
of this general relation.
The lines comprising the element supports of '
eighth wavelength, the input impedance will still
the tube of my invention may be considered from 60 be low in comparison with the characteristic im
pedance of the line, and although more power
a number of aspects, all depending on the gen
will escape than if optimum conditions are met
eral relationships above set forth, but in the
the amount of power wasted by such undesired
treatment here adopted they are generally con
radiation will be very ‘small.
sidered as divided into sections of quarter-wave
The section of the inner line comprising the
length, or thereabout, as this is believed to lead 65
cylinder 54 and column 25 terminates in the slider
to the simplest explanations.
We are interested in the impedance of the grid- .
?lament support line as viewed from the grid end,
5|, which, as it is of large area and makes good '
contact with both conductors, may be considered
as of zero impedance. This section may be tuned
but this impedance is dependent upon the termi
nating or output impedances of the various sec 70 to exactly one-quarter wave by moving the slider.
Due to the spacing between the two conductors
tions and, therefore, in order to determine what
the grid-end impedance will be, we must consider
the various elements, section by section, starting
from the outermost or lower end of the tube as
shown in Fig. 1.
the characteristic impedance of this section of
transmission line is high, and if the resistance
of the line were zero the input impedance would
75 be in?nite. Actually it may always be made to
~ exceed 100,000 ohms and under optimum condi
tions may reach. ten times this value. This sec-'
tion therefore forms a tuned radio-frequency
choke of extremely high impedance interposed
between the ?lament-grid structure and the out
side world, and the impedance involved is so high
that practically all energy reaching it is re?ected
back to its source.
What actually happens can be expressed more
16 -
This eifect is obtained by means of the irregu
larity introduced by the low-impedance line sec- '
tion constituted by the slider 29. From the top
of the high impedance section already described
to the slider is a length of relativelyhigh imped
ance line of less than ‘A wawelength which there
fore appears as va capacity variable from zero to
some small value as the slider is moved to change
its length from zero toward M4. To this is con
nearly in the terms of low frequency power line 10 nected the relatively great capacity of the slider
transmission if we think of the antenna as a
portion of the line about 1,41 x in length, but pre
senting an effective capacity many times as great
as and apparently in parallel with that of the
lower section, so that moving the slider to change
the length of the section below it changes the
load which is fed by a line terminating immedi
ately above the top of the column 54. Current
fed to this line from the central column 25 must
proceed down the column, across the slider, and
back to the top of-the conductor 54, since owing
to-skin eifect none will ?ow transversely through
apparent capacity'as viewed from above rela
tively little. Therefore a very short length of
the high impedance line above the slider is all
current meets an enormous impedance-say
that is necessary to tune this effective capacity
100,000 ohms. From there the line continues 20 to resonance, thus completing the quarter-wave
down the outside of conductor 54 to the antenna
section of line and bringing the node or quarter
and back within the column 51 to the terminus
wave point of the composite section a small dis
above the top of conductor 54. This latter length
tance above the upper slider face. The distance
of line, including the load imposed by the an
between the slider and the node will vary with
tenna, has an impedance of, say 1 ohm, and since 25 frequency, of course, but only slightly with the
the voltage ‘available at the termini of the line
position of the slider.
will divide itself across this low impedance and
It has already been pointed out that the node
the high impedance line section in series there
is effectively equivalent to a short-circuit, and
with in the proportions of the magnitudes of those
hence, since by moving the slider we may move
impedances, and‘since the current ?owing at the 30 the position of the node, by so doing we may
input points of the respective sections is the same,
tune the uppermost section of the line includ
it follows that the energy delivered to the respec
ing the ?lament and grid. We have made that
tive impedances will also be in proportion to their
portion of the line below the slider and above
magnitudes, and only $500,000 of that delivered
the impedance loop relatively ineffective in tun
to the line will be transmitted to the antenna to
ing, so that we have an "elastic” or extensible
be radiated thereby-still less if optimum condi
quarter-wave section of line.
tions are met.
The ?nal or grid-?lament section may thus be
From still a slightly di?’erent aspect, the small
resonated or otherwise tuned to give optimum '
and largely resistive impedance offered by the
operating conditions. In the case of Fig. 1,
outer line is at a current node. We therefore 40 where capacity feed-back between anode I3 and
have a very small current ?owing, and therefore
grid cap 99 is used, the desired tuning of this
the value of FR is vanishingly small, the R in
section must provide a capacitive reactance.
this case being the apparent input impedance of
This is obtained by making the grid-?lament sec
the outer line and FR (practically) the energy
slightly longer than one-half wavelength or,
45 in other terms, tuning it to a slightly lower fre
From whatever aspect the matter be considered
quency than that of the desired oscillation, so
the result is the same: The sections of the trans
that as viewed at grid and ?lament it presents a
mission line above the current node terminate in
small anti-resonant capacitive reactance. Under
the wall of the conductor. In so ?owing the
what is equivalent to an open circuit, just as
these circumstances the ?lament-grid system
would a low frequency line connected across an 50 appears as a capacity in series with the capacity
ordinarily good insulator. There is some con
between the grid structure and the anode, and
sumption of power, which can be neglected in
further consideration, (as in the case of the in
this latter capacity is adjustable by varying the
position of the cap 99. When, therefore, the
potential of the anode swings, the grid will as
sulator) and the succeeding sections can be
treated as if they terminated at this point in an
sume a potential with respect to the ?lament
in?nite impedance. It should be noted, however,
that at the frequencies we are considering sub
stitution of an insulator for the line sections
would drop the impedance to a ?nite value and
introduce large losses through radiation and di
(and ground) which is intermediate between
cathode and‘ anode potential, and which bears
the proportion to the total potential between
anode and ?lament that the effective series
capacity between anode-grid and grid-?lament
bears to the apparent capacity between ?lament
. electric phenomena.
The design problem to be met, therefore, is the
design of a structure which, when terminated by
an impedance approaching in?nity, will have the
and grid.
swings the
the anode
properties of an anti-resonant circuit as viewed
from cathode and grid. This structure is pro
vided by two additional quarter-wave sections of
In other words, the arrangement is
a capacitive voltage divider which
grid potential in the same sense that
potential swings, and in ?xed and
predetermined proportion thereto. Since the
criterion for oscillation of the device is that the
grid and anode should swing in the same sense
The ?rst of these sections extends to include
the upper slider 29, and its design is such that its 70 and in step, the result is a highly effective capac
ity feed-back which is under control either by
electrical length may be changed in opposite sense
the actual capacity coupling with the
to its physical length; i. e., such that it may be
cap 99 why varying the effective resonant in
“?tted in" beneath the section above it even when
the same line.
put capacity of the grid-?lament circuit by
' the length of the upper section increases with de
creased frequency of operation or vice versa,
varying the position of the slider 29.
By the use of the ‘two sliders the device is thus
the position of the sliders the effective resonant '
centric therewith by an annular spacer‘ H4. The
accelerator grid I5 is supported from the inner
member by a tubular bracket H5, the end of
which ?ts within the conductor I I2 andis rigidly
secured thereto. A cooling pipe I", bent into a
ring to surround the accelerator grid, has its
ends brought down parallel to the support bracket
impedance of the ?lament-grid combination may
I I5and enters the inner conductor on either side
given its very considerable tuning range._ The
lower slider BI brings the current node to the
point where the antenna is fed; the upper slider
28 moves the nodal point immediately above it
, and thus tunes the ?lament-grid section. The
actual point of‘importance is that by adjusting
thereof, the ends of the pipe passing into the
desired, since the node above the slider 28 may 10 inter-conductor space distally of thespacer H4
and emerging through the ?ange H0. A tuning
be moved near enough to the rather large lumped
slider H9, which nearly ?lls the space between
cathode-grid capacity to embrace between the
the inner and outer conductors and does not
node and that capacity the exact small line in
'make actual contact therebetween, is operated
ductance required for tuning it. In actual prac
tice the e?ective impedance will be made capaci 15 by means of a hook I20 whose end projects
through a longitudinal slot in the conductor H2.
tive and small in comparison with the“ physical
A control rod I2I is threaded to the end of the
grid-cathode capacity, but it might, if desired,
be made to assume any value which may be
- equally well be ‘made inductive or resistive. Fur
' hook and emerges through a Wilson seal I22.
The supporting bracket H5 and cooling tubes
thermore, since the effective resistances in the
circuit are extremely low, and the losses are also 20 I H are carried up to the interspace between the
control grid and the boundary grid through an
small even though the circulating currents may
angular ?tting or shield I25,- which passes
' A system of transmission lines, chokes and
through a notch I21 cut in one side of the ?la- ,
ment support ring 6 I. This construction is shown
by-passes similar to that used in the ?lamenti
grid circuit is employed acrossv the ?lament to 25 in Figs. 1, 6 and 11, each of these ?gures showing
sections of the shield. The shield is electrically
prevent transmission of energy to D.-C. insu1a_
continuous with a pan I29 overlying and contact
tion and to prevent ?lament damage by R.-F.
ing the ?lament support ring ‘I4 and slotted im
currents. The actual ground point on the ?la
mediately above the ?laments, which forms an
ment circuit is the ?ange 'I on the outer casing
5 of the device. This, however, is unimportant 30 additional shield or barrier to separate completely
the anode and control-grid sections of the tube
and the effect of the'transmission line arrange
except at the points where intercommunication
ment may be considered as though the ground
is necessary or desired. The shield and pan
point were at the inner end of the ?lament.‘
therefore form one terminus, and the accelerator
vThis may be considered as terminus of a quar
grid and cooling pipe I I1 form the other terminus
ter wavelength coaxial transmission line compris
of the radio-frequency transmission line compris
ing the tubular conductors ‘I9 and 80, which is
ing the side tube I05 and the tubular conductors
open at its lower end, terminatihg in a high.
H2 and H3.
impedance. The transmission line impedance is
From what has gone before it' is believed that
again low, being of the order of, say 5 ohms, and
the line therefore forms a negligible series im 40 the operation ofthis arrangement will be readily
apparent. Again we have an antenna system
pedance as before, acting as a‘ by-pass to the
comprising the control rods I2I and cooling tubes
inner conductor. This, again, is a quarter waveH ‘I, plus the projecting end of the conductor H3,
length line with the pipe 62 at its inner con
which is fed by and oifers a relatively high im
ductor, terminating in a dead short, and there
pedance to a quarter wavelength transmission line _
fore offering very high impedance. As the po
of low impedance formed by the side tube I05
tential imposed across this impedance is merely
and the conductor H3, and there is accordingly
that which can build up across the short ?la
a radio-frequency by-pass between the grounded
ment, amounting to a few volts at most, the
escape of power through the ?lament support
outer case 5 and the tube I05 of the conductor
may be neglected, and the high impedance ef 50 H3, Within this there is another series section
fectively in series with the ?lament prevents cir
- of transmission line comprising the conductors
m and us and terminating in a short formed ' I
culation of R.-F. currents which might otherwise
by the spacer H4. This inner line is tuned-to a
cause hot spots and burn-outs.
quarter wavelength by means of the slider I20,
We are now ready to consider the mounting
of the remaining elements, 1. e., the accelerator 55 which acts as a loading capacity and increases
greatly the electrical length of the line. In prac
grid, boundary grid, and anode, which elements
tice this slider is moved back to a point from
are shown in elevation in Figs. 9, 15 and 13, re
which they line appears as a very large inductance
spectively. The accelerator grid is mounted
at the operating wavelength. The proper point
from a side tube ‘I05. which is welded to project.
through the wall of the housing v5 immediately 60 is that at which the remaining inductance and
below the ?ange 3. ' This side tube carries at its
outer end a ?ange III'I which is surfaced to re
capacitance of the line, considered from the grid
end, make it just a quarter wavelength vfrom the
inner end. to the shorting spacer H4, forming a
ceive the tubular glass insulator I09, andv the
very high impedance at the shield where the
latter, in turn, carries a terminal ?ange III].
This structure may best be seen in the enlarged 65 grid I5 and cooling tube I H are supported, and
preventing’ any appreciable power being transmit
detail view of Fig. 6. As in the case of the main
ted past this point to be radiated.- The capacity
tube envelope, the tie-bolts which hold the struc
of the grid I5 to the boundary grid 4 is large, and
ture together are omitted, but it will be under-'
stood that it is assembled in the same fashion
that to the control grid I6 is small; there is little
coupling tending to swing the accelerator grid
as is the main envelope with ground surfaces
reenforced by greased rubber bands or gaskets
I5, and it consequently tends to maintain very
nearly zero R.-F. potential.
III which form the seals. Two tubular conduc
tors are ?xed to and project inwardly from ?ange
As has already been described and as shown in
detail in'Fig. 16 the boundary grid 4 is ?rmly
II 0. The inner conductor H2 is spaced from the
outer conductor H3 and is held accurately con 75 clamped between the ?ange 3 and the anode
housing 2, and is therefore physically and-de?
is mounted concentrically within the pipe. I44 by
= nitely at the ground potential of‘ the housing.
means of a perforated cap I55 which ?ts over
The boundary grid and the anode face I3 again
\ form ‘the termini of a resonant line, comprising ‘
‘ the housing 2 as its outer conductor and a cylin
; drical anode body, designated by the general ref
erence character I30, within the housing. This ,
i resonant line is one-half wavelength long, and
the end of the pipe I44, its lower ~end passing
out through the discharge chamber I5I. The
cap compresses a rubber gasket I45. sealing the
joint between the pipe I44 and the anode body
to make it water and vacuum tight.
The upper end of ‘the pipe I54 isacentered in
the pipe I44 by means of a metal bellows I51
1 may be considered as terminating between the
§ inner face of the ?ange I and the end "I of the
which is sealed to both pipes and permits di?er
ential expansion between the two. Water is,<in
troduced into the pipe I44 through a side pipe
‘ anode body. This will be recognized as an open
. ended half wave line, and therefore of extremely
j high impedance when viewed from either end.
‘~ ' I59, and its course can be traced by the arrows
in the drawings through the outer pipe, the
f anode body are best shown in Fig. 8. The sup 15 perforations in the cap I55, the side pipe‘ I52,
1 port is from the mid- or quarter wavelength point
and thence around the baiiie cylinder I50 and
The construction and method of support of the l
1 of the anode, i. e.,-at a potential node, so that‘ l
= there is little tendency for power to escape from
1 the support structure. Such tendency as there
I is for power to leak from the support point is
1suppressed by either or both of two methods.
f First, and preferable in the cases where the tube
back through thecen‘tral pipe I54.
5 A
The action of the mounting follows the ‘prin
ciples already set forth, although the application ’
is somewhat different. A disc I60 is connected’
to the ?ange I4I both electrically and mechan
ically, and carries a cylinder IGI. . The pipe I44
j may be predesigned to operate at a ?xed wave- _ ‘
and the cylinders I40 and I6I form a transmis
length, is a movable plate I32 mounted on the
sion line one full wavelength long. Electrically
; sliding rod '50 of the Wilson seal ?rst described, 20 this might equally well be a half wavelength line,
1 and making contact with the ?ange I by means
but additional space is needed for the insulating
:of a spring skirt I33. This may be adjusted to
cylinder I42, which must withstand the. full
I bring the node of the resonant line accurately at
D.-'C. anode potential of 20,000 volts or more.
1 the point of support. This method of preventing
The length of this section is measured’from the
‘direct radiation from‘the anode was adopted in so anode and its housing, and the impedance at its
§the ?rst of these devices constructed. It was
outer end is very high, so that looking into it
:quickly found, however, that the plate I32 was
from the anode the impedance is also very high.
This high impedance is connected in shunt
principle of transmission-lin'e-choke support was
across the line formed by the anode body I30
%again employed to prevent power escape. In-the as and anode housing 2 very near the nodal. point,
1 construction then adopted and here shown a side
where the impedance of the latter line is low,
;tube I40 of relatively large diameter is welded at
and accordingly a very small portion of the cur
1 more useful as a tuning device, and therefore the
‘substantially the midpoint of the anode housing
rent ?owing at this point will take the high im- ,
12. ' The side tube carries a metallic ‘?ange “I,
pedance path to the outer world.
In other terms, the full wave line is connected
1 with a glass insultor tube I42 ?tted against it and
in turn carrying a terminal ?ange I43. Through .
1this terminal ?ange passes a pipe I44 which pro
;jects through a pass hole I45 in the side of the
janode housing and on the end of which the anode
‘body is attached. The action here will be de
iscribed following the mechanical description of
Ithe anode, as the expedients adopted are predi
jcated upon the necessities of the mechanical
so near the node of the main anode oscillator
circuit that only a few volts are effective‘ across
its. termini, and therefore very small currents ,
.5 and Z the large input impedance.
will tend to flow therein, representing a power
loss of V‘I/Z where V is the small input voltage
since the line is one wavelength long, only'the,
small voltage V will be e?ective to cause radi-
ation from the radiating system constituted by
j From the electrical point of view the anode so the end of the line. It should be noted, however,
;body is a simple cylinder with closed ends. Its
that by deliberately unbalancing the anode res
3complexity, as shown in Fig. 8, is due primarily
onator by means of the plate I32 the support
:to the provision for circulating cooling water
system can be converted to a horn antenna
within it, and to the provision of what may be
which can be made to radiate as much high
‘termed a "rough tuning” device.
frequency energy as the device will produce.
‘ Owing to the necessity for providing cooling
_It will be noted that the arrangement de
the body itself must be water-tight, and accord
scribed leads to and permits a new type‘of cav
ingly it is constructed of a ~?ared cylinder I41, to‘ ‘ ity resonator; -i. _e., one wherein various portions
1the ?ared end of which the anode face I3 is hard
may be operated at 'di?erent D.-C. potentials, so
soldered. The other end of the cylinder is closed 00 that D.-C. accelerations can occur while elec
‘by a threaded disc I40.
trons are within the resonant cavity.
Such ac- . "
1 The supporting pipe I44 enters the ?ared cyl
celeration is not always necessary or' desirable
‘inder I 4'! through an aperture in the side thereof. ‘ it is true, but there are occasions where it is
The end of the pipe is threaded into a boss I43
useful, and so far as I am aware, none of the
on an inner baille cylinder I50, which boss is sol
various constructions hitherto suggested or em
dered to the inner wall of the cylinder I41. The
ployed permit it.
boss I48 extends internally to form a cylin
It has already been stated that ?ne tuning of
drical chamber I5I, which connects by a side pipe
the anode resonator?can be accomplished by
1I52 through the end I53 of the ba?le cylinder, so ‘ means of the disc I32. Greater changes in wave
that water introduced through the pipe I44 is 70 length or operating frequency can be secured by
‘discharged directly against the active face I3
placing a cylindrical shell I62 around the anode
of the anode, and thence is forced around the
body. The effect of such a shell is twofold, since
exterior of the ba?le cylinder to reenter its open
it increases the capacitance of the line formed by
end. It can then return within the cylinder to
the body and the housing, thus tending to in
enter the open end of a return pipe I54, which "crease wavelengths or decrease frequency, but it
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