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Патент USA US2112967

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-April 5, .1938. Y
F. H. KROGER'
2,112,967
TRANSMITTING SYSTEM
Filed’Jan. 24, 1955
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ATTORNEY
2,112,957
Patented Apr. 5, 1938
UNITED STATES raten-'r orties f
2,112,967
TRANSMIT'EING SYSTEM
Fred lli. Kroger, Rocky Point, N. Y., assigner tc
Radio Corporation of America, a corporation
of Delaware
Application January 24, 1935, Seriai No. 3,259
ld Claims.
This invention relates to an improved short wave
(Cl. Z50-17)
plete transmitting system in accordance with thev
An object of the present invention is to provide
principles underlying the present invention.
In the single figure of the drawing, the various
a very simple and highly efficient short wave
stages of the sho-rt wave transmitter are labeled
f, transmitting system.
Another object is to provide a system which
enables the transmission of modulated short wave
stages are, in the order of their occurrence, the
transmitting system.
signals over a very wide frequency band and with
a substantially flat overall characteristic.
A further object is to provide a transmitter ar
l()
rangement which has high frequency stability
comparable with crystal control, but which dis
penses with the use oi" piezo-electric crystals.
A still further object is to provide an eñicient
short wave system capable of radiating waves of
the order of three meters, more or less, and of
providing an output which when unmodulated is
between 80 and 100 watts.
And a still further object is to provide a highly
„o advantageous assembly of elements which are in
herently rugged and free from critical adjust
ments and the like.
A feature of the invention lies in the combina
tion of single ended master oscillator and fre
quency control line, which requires no insulation
in the mechanics of the line. The oscillator is
thus in the simplest possible mechanical form and,
with the provision of a simple circuit, reduces
initial cost of equipment and maintenance to a
minimum.
Another feature lies in the manner of mounting
the equipment into a compact assembly which
enables easy adjustment and maintenance of ap
paratus. The entire radio frequency assembly is
mounted as an integral unit whereby there can
be no geometrical change.
A further feature resides in the use of lecher
wires for inductive coupling instead of lumped in
ductances, in order to obtain simplicity of tuning
and higher operating efñciency in the system.
These lecher wires are used with trimming con
densers so that with change in temperature there
will be a minimum change of electrical constants.
One advantage of the invention is that the fre
45 quency is maintained constant as long as the
oscillator is supplied with power which has rea
sonably constant voltage, that is, in a range plus
or minus one percent, and without the use of
50 numerous accessories which require adjustment
and maintenance.
Other objects, features and advantages will
appear in the subsequent detailed description
taken in conjunction with the accompanying
55 drawing which shows, diagrammatically, a com
and shown separated by dotted lines.
'I‘hese
single ended master oscillator MO, the single tube
frequency doubler
the push-pull intermediate
power amplifier IPA, I'P’A’, and the push-pull
power amplifier PA, P'A’.
The master oscillator stage comprises a single
ultra high frequency tube MO between whose grid
ifi
3 and cathode K is loosely coupled a quarter wave
length frequency control transmission line I.
Line l is a low loss concentric tube affair havingl
inner and outer conductors, and has the effect of
a sharply tuned resonant circuit whose reactance
changes rapidly with frequency, and it is this
characteristic which is utilized to keep the fre
quency of oscillator MO constant.` Since the res
onant frequency of the concentric line is deter
mined chiefly by its length, it is provided with a
sylphon bellows and invar rod, or equivalent ar
rangement S for maintaining the overall length
of the inner conductor constant despite ambient
temperature fluctuations.
Line l is designed to be a quarter wave length
long, electrically, for reasons of reliability and
simplicity. The diameters of outer and inner con
centric tubes are chosen to give a compromise
between space economy and a high reciprocal of
power factor; the outer tube serving as a support
for the panels upon which are mounted substan
tially all the radio frequency units. For greater
frequency stability, line l is made integral with 35
the radio frequency units and kept free from
vibration which is ñltered out. In practice, the
line and transmitter unit are suspended by very
ñexible helical springs, and the entire unit secured
to a rack which, in turn, is mounted on shock
absorbers. For a more detailed description of line
I as employed herein, reference is made to my
'copending application Serial No. 1489, filed Jan
uary 12, 1935.
As an illustration of the frequency stability of 45
the line, in using the twelfth harmonic of a crystal
controlled oscillator for comparison, it was found
that with a variation of 9° C. in ambient temper
ature, line l varied no more than the crystal which
maintained Aits frequency within .0005% over this
change in ambient temperature.
Line l is made single ended and the frequency
produced by oscillator MO is doubled in the sub
sequent stage.
Any other arrangement would,
Ordinarily, give too long a line. In order to re
g
2,112,967
duce possible undesirable reaction, the generated
frequency is taken as one-half that radiated,
which in one practical embodiment was 45.9
megacycles.
A thermo-galvanometer M is loosely coupled to
the inner tube of line I by means of exposure
with respect to each other and lecher wires I8 and
is tuned to twice the frequency of the master
oscillator frequency.
A balancing air condenser 2| in the plate cir
cuit of FD makes circuit I8 symmetrical with re
spect to ground and is set to a value approxi
plates for determining the amplitude of oscilla
tions of the line.
Between grid 3 of vacuum tube MO and line |
10 there is provided the conventional grid leak GL
which gives part of the bias for the grid, thus
enabling automatic adjustment for variation in
tubes.
The filament power leads for the legs of cath
side of the mechanical center are contacted by a
15 ode K which are above ground potential and
which are maintained at the same radio frequen
air choke coil.
cy potential by by-pass condenser 4, are part of
a double coil 5 for controlling regeneration of
oscillator MO. The double coil 5 serves to bring
20 out the filament leads in known inductive rela
v tion to each other.
Condenser 1 is a Vernier for
varying the inductance of coil 5, and condenser
6 is a by-pass condenser to ground. A spark dis
charge gap |00 serves as a protective circuit in
25 case of breakdown of tube MO. The filament cir
cuit tuning is arranged to give suiiìcient regener
ation at the frequency of line | but to cause 0s
cillations in MO to cease when line | is short cir
cuited.
30
A 220 volt, 60 cycle, alternating current som-ce
energizes the filament of the oscillator through a
transformer |06 and a copper oxide rectifier |05.
The direct current obtained from rectifier |05
eliminates the small 120 cycle modulation which
35 alternating current on the filament would cause
due to the resulting variation in bias. All other
filaments are supplied directly from the 60 cycle
supply.
In the output of triode MO is a parallel tuned
40 circuit comprising lumped inductance 9 and va
riable condenser 8 coupling oscillator MO to the
grid of the following frequency doubler stage.
mately equal to the plate-grid capacity of FD;
the condenser which consists of two discs ad
justable with respect to each other is then varied
until the voltage node of the plate circuit is ap
proximately at its mechanical center, a condition
which is indicated by equal drop in wave meter
indication when places equal distances on each
testing rod.
Element I9 is a radio frequency
Tube FD is also provided with a grid leak GL',
a protective spark gap IGI, filament tuning I5 to
control regeneration, variable condenser I6 and
condenser 58, which elements correspond re
spectively with elements GL, gap |00, double coil
5, condensers 'I and 5 previously described in con
nection with master oscillator MO and used for
the same purposes. Other corresponding ele
ments also appear in the subsequent power stages
in respectively corresponding locations and for
similar purposes, and hence will not be referred
to later.
The intermediate power amplifier stage com
prises a pair of push-pull connected vacuum Sil
tubes IPA and I’P'A’ for amplifying the out
put of doubler stage FD and for exciting the grids
of the succeeding power amplifier tubes. The in
put circuit of IPA and I’P’A’ comprises a lecher
wire system 28 which is bridged by a tuning air ¿~ Li
condenser 3| and which is coupled to the lecher
wires I0 in the output of frequency doubler FD.
The coupling of doubler plate circuit I8 to inter
mediate amplifier grid circuit 28 is varied for op
timum excitation of tubes IPA and I’P’A'. The L
output circuit of this intermediate power stage
Condenser 8 is a Vernier which provides a con
also includes a pair of lecher wires 32 which are
coupled through a lecher wire line |02 to the
venient mechanical method of varying induct
grids of the succeeding stage. An air condenser
45 ance 9, and condenser I0 is a by-pass condenser
to ground.
In one embodiment used in practice, master
oscillator MO delivered about 80 watts, of which
about 20 watts went to the grid of the frequency
50 doubler stage and 60 watts to line I. The tuning
of condense-r 8 varies the ratio of the energy de
livered by MO to the line | and that delivered to
the grid of the frequency doubler. The greater
this ratio, the more will be the line current, and
55 the less the excitation to the doubler grid, and
at the same time the greater will be the frequen
cy stability, as the line will be operating nearest
to its natural frequency. A compromise is found
preferable whereby frequency stability is satis
60 factory and there is sufficient grid excitation in
the doubler to operate the intermediate amplifier
at something less than best efficiency.
The frequency doubler stage comprises the
vacuum tube FD which serves to excite the sub
sequent intermediate amplifier stage with energy
of double the frequency of that obtained from
oscillator MO. Grid I3 of tube FD is connected
to the tuned input circuit comprising inductance
I I and condenser I2 tuned to the frequency of the
70 output of oscillator MO. Inductance || is not
tightly coupled to inductance 9 and optimum
grid coupling is rather loose and is such as to give
rather sharp tuning for grid and plate. The out
put of doubler tube FD comprises variable air
75 condenser Il composed of two discs adjustable
Cil
29 composed of two spaced discs adjustable with ,
respect to each other aids in tuning the lecher
wires 32.
A pair of neutralizing air condensers 30, 34
compensate for the plate-grid capacities of the
associated tubes. Element 33 is a combination of
choke and parasitic resistor in the form of a
coil of resistance wire, the resistance preventing
push-push parasitic oscillations. A convention
al grid bias GL2 is in series with choke 33.
The power amplifier or output stage also com
prises a pair of push-pull vacuum tubes PA and
P’A’ which are arranged similarly to the tubes
of the preceding intermediate amplifier stage.
The purpose of this output stage is to further
amplify the carrier oscillations, and it is this 60
stage which is modulated and excites the anten
na. The output of the power amplifier is of the
same frequency as the intermediate amplifier
and is coupled inductively to the load circuit con
sisting of an inductive arrangement 56 and load (I5
adjustment inductances 51, the latter each com
prising ten turns of #10 wire, one inch in diam
eter and approximately two inches long.
For utilization purposes, it is preferred to em
ploy an antenna comprising a plurality of dou
blets of the type described in Carter application
Serial No. 342, filed January 4, 1935.
The transmitter is capable of being either fre
quency modulated or amplitude modulated by
connecting switch blade 53 in the plate circuit
3
2,112,967
of the last power amplifier, either to the upper
or lower contact respectively, and by using known
modulating means, not shown.
The elements of the transmitter circuit are all
completely shielded and mounted on panels sup
ported by line l.
In tuning the short wave transmitter, the iila
ment tuning of MO is set so that the master
oscillator will not oscillate when line l is short
circuited, after which the ñlament tuning is set
for maximum line current. In the intermediate
stage, the neutralizing condensers are each first
set at a capacity approximately equal to the
plate-grid capacity of the tubes. Then, with
15 no plate voltage and a grid meter in circuit, the
grid circuit is tuned. The plate circuit is tuned
next and the dip in the grid meter noted as
the tuning point is passed through. The neu
tralizing condensers are each changed an equal
amount and again the grid circuit is tuned. The
plate circuit is also tuned again and the grid
meter observed. If the dip in the meter is greater
at the tuning point than previously, the neutraliz
ing condensers should be changed in the opposite
25 direction.
This method oi setting the neutraliz
ing condensers is continued until no dip is noted
in the grid meter when the plate circuit is tuned,
after which the grid meter is taken out of the
circuit and the plate voltage applied, and the
30 plate circuit again tuned, the last tuning being
indicated by the wave meter. The coupling of
the doubler plate circuit to the intermediate
ampliñer grid circuit is varied Íor optimum exn
citation of the intermediate amplifier. The ñnal
35 power amplifier stage is tuned in the same man
ner indicated above for the intermediate amplifier
stage.
What is claimed is:
l. In combination, an electron discharge de
vice having anode, cathode, and grid electrodes,
means for maintaining said cathode above ground
radio frequency potential, a tuned input circuit
connected between said grid and cathode elec
trodes, a source of radio frequency energy coupled
45 to said input circuit, and a tuned output circuit
connected between said anode and cathode, said
tuned output circuit comprising a pair of lecher
wires conductively connected together at one of
their adjacent ends and capacitively coupled to
50 gether at their other adjacent ends, and a utiliza
tion circuit inductively coupled to said output
circuit.
-
2. A frequency doubler comprising an electron
discharge device having anode, cathode, and grid
Ui Ul electrodes, means for maintaining said cathode
above ground potential, a, tuned input circuit
connected between said grid and cathode elec
trodes tuned to a predetermined frequency, a
source of radio frequency energy coupled to said
60
input circuit, and a tuned output circuit con
nected between said anode and cathode and tuned
to a frequency twice that of said input circuit,
said tuned output circuit comprising a tuning in
ductance in the form of a pair of parallel con
ductors, means for varying the tuning of said out~
put circuit, means for making said pair of con
ductors symmetrical with respect to ground, and
a utilization circuit inductively coupled to said
output circuit.
70
3. In combination, an electron discharge device
having anode, cathode and grid electrodes,
means for maintaining said cathode above ground
potential, a tuned input circuit connected between
said grid and cathode electrodes, a source of radio
frequency energy coupled to said input circuit,
and a tuned output circuit connected between said
anode and cathode, said tuned output circuit
comprising a tuning inductance in the form of a
pair of parallel conductors, an air condenser
bridged across one end of said conductors for
varying the inductance of said pair of parallel
conductors, and an air condenser coupling one
plate of said ñrst air condenser to ground for
making said pair oi conductors symmetrical with 10
respect to ground.
4. In., combination, an electron discharge device
having anode, cathode and grid electrodes, a
tuned input circuit connected between said grid
and cathode, a condenser connected across the 16
legs of said cathode for maintaining both sides
thereof at the same radio frequency potential, a
heating source for said iìlament, leads connecting
the iegs oi said cathode to said source, and a coil
located between each of the legs of said cathode 20
and its associated lead for controlling regenera
tion, a condenser for varying the inductance of
at least one of said coils, a resistance connected
across said leads, and a connection from a point
intermediate the ends of said resistance to ground, 25
a tuned output circuit comprising a pair of lecher
wires between said anode and cathode, and a
utilization circuit including another pair of lecher
wires coupled to the lecher wires- of said tuned
30
output circuit.
5. A combination in accordance With claim 4,
characterized in this that said electron discharge
device is a frequency multiplier and said utiliza
tion circuit is a pair of push-pull connected power
ampliñer electron discharge devices.
35
6. In a sho-rt wave transmitter circuit, a pair of
push-pull connected electron discharge devices
each having anode, cathode and grid electrodes,
the corresponding electrodes of said devices being
coupled together, a tuned input circuit connected 40
between said grids and a tuned output circuit
connected between said anodes', each of said tuned
circuits comprising a pair of lecher wires, a neu
tralizing condenser connected between the anode
of each device and the grid ofthe associated de' 45
vice, means for maintaining the cathode of each
device above ground potential, a connection from
a point in each tuned circuit symmetrically dis«
posed with respect to the lecher wires therein to
the cathodes, and means for biasing said grids 50
negative and said anodes positive with respect to
said cathodes.
_
'7. In a short wave transmitter circuit, a pair
of push-pull connected electron `discharge devices
each having anode, cathode and grid electrodes,
the corresponding electrodes of said devices being
coupled together, a tuned input circuit connected
between said grids and atuned output circuit
connected between said anodes, each of said
60
tuned circuits comprising a pair of lecher wires,
a neutralizing condenser connected between the
anode of each device and the grid of the associ
ated device, means for maintaining the cathode
of each device above ground potential, a connec
tion from a point in each tuned circuit symmetri 65
cally disposed with respect to the lecher wires
therein to the cathodes, means for biasing said
grids negative and said anodes positive with re
spect to said cathodes, another similarly con 70
nected pair of push-pull coupled electron dis
charge devices, and a pair of lecher wires induc
tively coupling the tuned output circuit of said
ñrst push-pull circuit with the tuned input cir
cuit of said last push~pull circuit.
75
4
2,112,967
8. In a high frequency communication system,
an electron discharge device having a high frequency output circuit and coupled thereto a cir
cuit tuned to an ultra high frequency, said tuned
circuit comprising a pair of lecher Wires and a
variable air condenser bridging said lecher wires
for tuning said circuit, said lecher wires being
conductively short circuited at one of their ad
jacent ends and bridged by said air condenser at
the other of said adjacent ends, whereby with
change in temperature there is a minimum
change in the electrical constants of said tuned
circuit.
9. In combination in an ultra high frequency
circuit, an electron discharge device having an
ode, cathode and grid electrodes, means for main
taining said cathode above ground radio fre
quency potential, a tuned input circuit connected
between said grid and cathode electrodes, a
20 source of radio frequency energy coupled to said
input circuit, and a tuned output circuit com
prising a pair of lecher wires conductively con~
nected together at one of their adjacent ends
and capacitively coupled together at their other
adjacent ends, a connection including an induc
tance coil in series with a source of potential eX
tending from said cathode to those adjacent ends
of said lecher wires which are conductively con
nected together, and a connection from said an
30 ode to the other ends of said lecher wires.
10. In combination in an `ultra high frequency
circuit, an electron discharge device having an
ode, cathode and grid electrodes, means for main
taining said cathode above ground radio fre
35 quency potential, a tuned input circuit connected
between said grid and cathode electrodes com
prising a coil and a condenser in parallel with
said coil, a source of radio frequency energy
coupled to said input circuit, and a tuned output
circuit comprising a pair of lecher wires conduc
tively connected together at one of their adjacent
ends and capacitively coupled together at their
other adjacent ends, a connection including an
inductance coil in series with a source of potential
45 extending from said cathode to those adjacent
ends of said lecher wires which are conductively
connected together, and a connection from said
anode to the other ends of said lecher wires.
11. A transmitter in accordance with claim ’7,
50 including a source of high frequency energy cou
pied to said tuned input circuit of said first push
pull circuit, and means for both frequency and
amplitude modulating said transmitter connected
to the tuned output circuit of said last push-pull
55 circuit.
12. In a short wave transmitter, a single ended
master oscillator comprising an electron dis
charge device having anode, cathode and grid
electrodes, a tuned input circuit comprising a
quarter wave length concentric frequency con
trol line coupled between said grid and cathode
electrodes, an output circuit for said oscillator, a
frequency doubler comprising an electron dis
charge device also having anode, cathode and
grid electrodes, a tuned input circuit connected
between said last grid and cathode and coupled
to the output circuit of said oscillator, an output
circuit tuned to twice the frequency of said oscil
lator coupled between the anode and cathode
electrodes of said frequency doubler, said last cir 15
cuit comprising a pair of lecher wires conductive
ly coupled together at one of their adjacent ends
and capacitively coupled together at their other
adjacent ends, and an electron discharge device
amplifier having an input circuit coupled to said 20
lecher wires, said input circuit of said amplifier
also comprising a pair of similarly arranged
lecher Wires, a utilization circuit coupled to said
amplifier, an-d means for maintaining the cath
`odes of said oscillator, frequency doubler and 25
amplifier above ground radio frequency potential.
13. A frequency multiplier comprising an elec
tron discharge device having anode', cathode and
grid electrodes, means for maintaining said cath~
ode above ground potential, a tuned input circuit 30
connected between said grid and cathode elec
trodes tuned to a predetermined frequency, a
source of radio frequency energy coupled to said
input circuit, and a tuned output circuit connect
ed between said anode and cathode and tuned to a
frequency which is a multiple of that of said in
put circuit, said tuned output circuit comprising
lecher wires and a variable air condenser bridged
across said lecher Wires.
'
40
14. In a high frequency communication system,
a, non-oscillating electron discharge device hav
ing a high frequency input circuit and coupled
thereto a circuit tuned to an ultra high frequen~
cy, said tuned circuit comprising a pair of lecher
wires and a variable air condenser bridging said
lecher wires for tuning said circuit, said lecher
Wires being conductively short circuited at one of
their adjacent ends and bridged by said air con
denser at the other of said adjacent ends, where 50
by with change in temperature there is a mini~
mum change in the electrical constants of said
tuned circuit.
FRED H. KROGER.
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