Cutler-Hammer AIL 124 manual 

AI L TYPI 12,4
POWER
...
OSCILLATOR
I
J u'';'' l.9.,6·0·
Airborne Instruments Laboratory

FIGURE '-I.
TYPE 124 POWER OSCILLATOR, FRONT VIEW

TABLE OF CONTENTS
Page
.....-...-..
Section I--General Description
1-1
Section 3--Inatallatlon
Section 2--Theory of Operation
Section 4--0peration
1 .
General
2.
Inspection
3·
Installation
4. Load
1-1
1-1
1-2
1-2
2-1
2-1
2-1
2-5
2-6
2-8
2-9
3-1
3-1
3-1
3-1
3-2
4-1
4-1
4-1
4-2
4-2
4-3
4-5
General
Description
Characteristics
Tube Complement
Ge ne r-aI
Radio-Frequency Oscillator
Audio-Frequency Oscillator
Modulation
High-Voltage Power Supply
Low-Voltage Power Supply
Pre-Operation Procedure
Starting Equipment
Oscillator Adjustment
Frequency-Range Settings for RF Oscillator
Changing Ranges
Modulation Adjustments
4.
1 ,
2.
3.
4.
1.
2.
3.
5.
6.
1.
2.
3.
4.
5.
6.
1

Section 5--Ma1ntenance and Trouble-Shooting
1.
2.
3.
4.
5.
6.
7.
8.
General
Replacement of Oscillator Tube
Repair
Removal
Depth Setting of Feedback Assembly
Counter Calibration
Trouble Analysis of Cavity
voltage Measurements
Resistance Measuraments
Table of Replaceable Parts
11
Page
--..-.
5-1
5-1
5-1
5-2
5-2
5-2
5-4
5-5
5-8
5-9
5-10

Figure
Frontis-
piece
1-1
1-2
2-1
2-2
2-3
2-4
2-5
2-6
2-7
5-1
LIST OF ILLUSTRATIONS
Type 124 Power Oscillator
Type l2~ Power Oac111ator
J
Front View
Type 124 Power Oscillator) Top and Bottom
Views
Type 12
l•
Power Oscillator, Schematic Diagram
Tuning Curve for Low-Low-Frequency Range
Tuning Curve ror Low-Frequency Range
Tuning Curve for High-Frequency Range
Type 124 Power Oscillator
J
Rear View
Pulsing Characteristic of Type 124 Power
Oscillator
Mini.mum. Pul ae Length Obtainable with Modified
Circuit
Type 124 Cavity Parts Identification
111 .

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':,," .... ::.,';" -=--i:~·':.~.~:···~·~··
c .::-.:. ...•. -
~~,~ ~
"'0
FRONTISP\ECE. ,.'(PE \24 POWER OSCILLATOR
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-1

SECTION 1
GENE:RAL DESCRIPTION
1. GENERAL
The Type 124 Power Oscillator (Figures 1-1 and 1~2)
provides sIgnals at rrequenc1ea rrom 200 to 2500 Me 1n three
ranges; it delivers continuous-wave, sine-wave modulated,
e·quare-wave modulated, or (u.nder certa.1n conditions) pulae-
modulated signals. An internal audio oscillator permits sine-
wave modulation of the RF oscillator at either 400 cps or
lOOO,cpSj an external oscillator can be used to drive the
modulator at frequencies trom 20.CpB to 150 kc. External
sources or square waves or pulses can also be used to modulate
the oscillator. Pure pulse output Is not obtainable under all
eondd t Lons , This limitation 1s described more fully in Sec-
tion 2, paragraph 4d.
2. DESCRIPTION
The Type 124 Power Oscillator 16 designed for
either bench-top or standard relay-rack mounting (for rack
.mounting, the two side handleB must be removed)n It is
housed in a single chassis. All connectors necessary ~or
the operation of the unit are located on the front panel--
with the exception of the AC input, which 1s located at the
rear o~ the unit. Front-panel contro18 are provided ,for
operation over the three ranges; to select a particular
range, however adjustments at the rear of the unit are nec-
essary. The type or modulation is Belected by means of a
six-position switch on the front panel.
1-1

3. CHARACTERISTICS
J
d.
Output impedance
e.
Power input
f.
rvlountlng
g. Weight
J+ •TUBE
COM PLEJJ!ENT
Symbol Type
...........-
V10l
6SN7
VI02
(A)
6SN7
(B)
6SN7
VI03 807
VI04
5R4GY
VI05
5R4GY
VI06 NE51
(neon)
VI07
2C39A
a.
b.
c.
Frequency ranges
(nom1nal)
Types of signal
RF power output
(nominal)
1-2
200 to 500 Me
300 to 900 Me
900 to 2500 Me
Continuous wave; amp11tude-
.modulated sine wave, square
wave, and pulse (l~mlted)
In excess of 10 watts at
200 ·Me, 20 watts at 600 Me,
lOwatta at 1500 Me, and
2.5 watts at 2500 Me
50 ohms
180 watts at 115 volta,
50 to 60 cps
Standard relay rack,
lO.5-1nch high panel
78 pounds
Use
Audio oscillator
Pulse polarity changer
Preamp11rler
Modulator
High-voltage rectifier
Low-voltage rect1C1er
Oscillator limiter
RF oscillator

SECTION 2
THEORY OF OPERATION
.1. GENERAL
The TYpe 124 Power Oscillator (Figure 2-1) consists
essentially or an RF oscillator, an AF osoillator, a modulator,
.and two power supplies .
.2.
RADIO-FREQUENCY OSCILLATOR
The source of RF power 18 a resonant-cavity oscil-
lator built around a 2C39A disk-seal triode tube. The oscil-
lator circuit Is composed of adjustable coaxial lines.
a . STRUCTURE
The 2C39A tube (VI07) is mounted coaxially Within
the cylindrical lines at the rear or the oBcillator Btructure~
which 1s closed by a metal end plate. The grid
J
plate, and
cathode contact surfaces of the tube are contacted all the way
around by spring contacts. The grid of the tube Is connected
.. directly to the end of the middle cylinder; the plate and
cathode elements are connected to the outer and inner cy11nders
J
respectively, through-blocking capacitors Cl14 and el15.
Two plungere slide between the concentric lines to
.vary the lengths of the active portions of the lines that form
resonant cavities. The plungers are driven by lead screws
\
from the gear·box and the main tuning knob. Provision 1s
,
made for adjusting the grid-cathode (cathode) plunger independ-
ent or the grid-plate (plate) plunger by pushing in on the
tuning knob; this operation disengages the plate-plunger drive.
If the plungers are properly adjusted, the oscillator will
operate on odd quarter-wavelengths.
2-1

b. MODES OF OSCILLATION
For the two low-frequency ranges (200 to 500 Me and
300 to 900 Me), the coaxial oscillator 1s operated on the
.fundamental ("/4) mode; for the hlgh .. frequency range (900 to
2500 Me), the cavity 15 operated on the 3~/4 mode. In either
case, the setting o~ the plate plunger is the primary rrequency
determinant. For a given plate-plunger Betting, however,
there are always two settings of the cathode plunger that
will produce oBc111at1ona--and there may be as many as four
settings. These oscillations, which are quite d1st1nct~ cor-
respond to the ~/4J 3A/4, 5A/4, and 7\14 mode8. On the low-
t'r-e que ncy r-ange s , only the A/4 mode and a weak 3X/4 mode appear-;
on the high-frequency range, all of the modea may appear~
Bee8.use of t.h is , it is necessary to adhere rather' closely to
the tuning curves (Figures 2-2, 2-3, and 2-4) to keep from
working on an undesired rrequency.
Some deviation from the average tuning curves occurs
wi th d1 f'f'erent 2C39A t ube s . Occ ae Lona Ld y , 1t may be necessa:ry
to check the mode of oscillation With a frequency meter.
c. FEEDBACK ASSEMBLIES
The feedback coupling required to produce oscilla-
tion on the fundamental A/4 mode (200 to 50D Me and 300 to
900 f"1c) 1s obta.ined from its respective aase.mbly (Figure 2-5)
that provides capac1 tl ve ree dback • These assemblies consist
of taba ln the plate cavity, connected through insulated probes
to a ring 1n the cathode cavity.
Feedback coupling required to produce oscillation
. in the 3 VJt mode {900 to 2500 Me} is obtained from an asse.mbly
(Figure 2-5) that provides inductive feedback. This assembly
cona:tsts of three S-shaped loops; one loop or each US" is in
the cathode cavity, and the other loop is in the plate cavity.
Only one o~ these assemblies 1s used at anyone time; the
unused assemblies are each held 1n a holder provi.ded on the
2-2

inside 5ur£ace of the rear access door. To change rrequenoy
ranges
6
it 1s necessary to disassemble the rear of the oscil-
lator unit and to install the appropriate feedback assembly.
d • TUNING RANGE
The lowest frequency to which the o8c111ato~ can be
tuned 1s determined by the mechanical limit of travel of the
plate plunger away from the tube j, th1sminlmwn rrequency is
about 180 Me. The highest rrequency at which the oscillator
can be used 1s determined primarily by the limitations of the
oscillator tube. Power output can be obtained as high as
2700 Me, but the limit of useful output will vary considerably
with different 2C39A tubes. TUbes should be selected for best
performance at the high-frequency end of the tuning range.
e. TRACKING
The lead screws that dr1ve the cathode and plate
tuning plungers are geared in such a manner that nearly per-
fect tracking 1s accomplished over the entire A/4 mode. Best
results will be obtained if the cathode and plate plungers are
aligned .for optimum output at a reading o.f 5500 on the plate
counter. With a load having a low SWR over the frequency
r-ange , single-dial operation .from 300 Me to over 800 Me should
be possible.
Tracklrlg on the 3A/4 mode is not automatic, and 1t
will usually be necessary to trim the adjustment o£ the
cathode tuning every 100 to 200 Me.
f • OUTPUT COUPLING
The IlF output 15 coupled to the cay! ty by an adjust-
able probe. Maximum pickup Ls obtained by t ur-nt ng the coupling
knob clockwise against its stop. Because the RF field within
the cavity changes with frequency,
S ; 1_ •• U III • I' 9111 Tt When
operating in this range, inductive coupling is prOVided by
2-3

mounting a coupling loop (Figure 2-5) so that it is capacit1vely
coupled to the probe. For satisfactory coupling above 1800 Me,
it 1s usually necessary to remove the coupling loop. The posi-
tion of the coupling loop is adjusted from the rear of the
oscillator unit by loosen1ng the loop-retaining screw
1
sliding
the loop in or out~ and tightening the screw to hold it in
position.
g. BLOWER CIRCUIT
The oscillator tube 1s cooled by forced air from
blower BIOI. The blower motor starts when the FILAMENT POWER
switch 1s turned on. Do not operate the un1t 1f the blower
does not start. (See Section 5, paragraph 1.)
h. CATHODE BALLAST RESISTOR
The oscillator-tUbe cathode bias resistor consists
of a standard 40-watt Mazda lamp ·(R126)~ wh1ch has the property
of increasing its resistance with increasing current. This
provides an automatic bias that improves the stability of the
oscillator.
i . METERS
The OSCILLATOR GRID and the OSCILLATOR PLATE meters
indicate their respective currents when the unit 1s operating
as a CW oscillator or when it is modulated by sine-wave s1gnals.
~hey are not in the circuit when the oscillator 1s being pulsed
or mo du La ted wi th square waves.
The RELATIVE POWER meter
J
in conjunction with m1cro-
match coupler Z101, samples and converts RF power to a DC volt-
age that carl be read Of. the RELATIVE POWER meter. This voltage
indication has SOIne proportional relationship to incident power.
This differs from net power to the load by only about 10 percent
for values of SWR as high as 2.0 and is considerably more
accurate for lower values of SWR. S1n.ce the m.i cr-omat ch coupler
is I'r-e quency -e en st ti ve and the SWR of the load ~'i:"ll vary over
2-.4

the rrequency range or the oscillator, a direct power ca11bra~
t10n would be misleading. However~ tor matched-load conditions
at any g1 ven frequency, an increase in the rea'ding of the
RELATIVE POWER meter will indicate an increase in power to the
load in accordance with the relationship listed in Table 11-1.
TABLE I1-1
RF Power in Percent
or Full Scale
o
5
10
15
20
25
30
40
50
60
70
80
90
100
Meter Deflection in
Percent of Full Scale
q
00.0
13.6
22.9
'30.9
37.4
43.1
48.5
57.7
65.7
73.1
80.1
Err .0
93.7
100.0
3. AUDIO-FREQUENCY OSCILLATOR
The Type 124 Power Oscillator contains an AF osc11-
lator (V10l) that can be used to modulate the RF oscillator
with either a 400- or alOOO-cps 8ignal. This oscillator is
turned on by means of the MODULATION SELECTOR switch (Fig-
ure 1-1). The AF oscillator is designed to pr-oduce a wave-
form relatively rree from distortion.
2-5

4. MODULATION
The Type 124 Power Oscillator can be modulated with
a variety of waveforms. The type of modulation 1s selected
by means of the MODULATION SELECTOR sw1tch on the front panel.
The degree of modulation for all positions of the
MODULATION SELECTOR switch except SQ. WAVE is controlled by
means of the MODULATION GAIN control.
a. AF MODULATION
Sine-wave modulation Is provided by the internal
AF oscillator whe n the MODULATION SELECTOR sw1 tch 1s turned
to 40C)"'" or 1000"'. Modulation for the sine waveforms 1s of
the parallel or- Reising .t.ype and is accomplished by means of
a type 807 tube (V103) and a modulation choke (L104). VI02B
is a preampllfler ahead of the modulator tube.
b. CW OSCILLATION
T11e Type 124 Power Oscillator will operate unmodu-
lated to fUrnish CW oscillation when the MODULATION SELECTOR
Bwitch 1s turned to CWft
c. EXTERNAL MODULATION INPUT
:;J F.
Wi th the MODULATION SELECTOR swl tell turned to EXT
and an external source of modulation connected to the panel
t.er-nu na Ls mar-ked EXTERNAL I.NPUT .. the RF oscillator can be
modu.lated at, I'r-e qu e nc ies fronl 20 cps to 150, kc wi th at least
40 percent modulation. Modulation at frequerlcieB as high as
950 kc 1s po e sLb Le wi th a reduced m.odulation percentage.
About 3 volts is required from the exterrial source~ The
in.pu tLmped arice is 10, ()OC) ohms.
d. PULSE MODULATION
For pulse operation, an external source of pulses
must be c orine c t ed to t.he panel receptacle marked PULSE rnpUT.
Whe11 the MOD1JLATION SELECTOR swi tell is turned to PULSEJ the
2-6

connections to VI03 (a type 807 tUbe) are changed to make 1t
a conventional pulse modulator. Between pulses, Cl12 is
char-ged through R120; during this period, the modulator tube
(VI03) 16 biased near cutoff. The oscilla.tor is also biased
by means of a cathode resistor (R124). When the modulator is
triggered, 0112 1s effectively placed between the osc111ator~
tube cathode and the ground, reducing the cathode bias and
permitting the tube to oscillate.
At low rrequenc1es (below 1500 Me), it will be
found that some CW oscillation occurs between pulses. On
the A/4 model the ratio of peak pulse power to CW power is
about 2.2 to 1 at 300 MC
J
rising to about 100 to 1 at 800 Mc.
On the 3A/4 mode, the ratio will be about 200 to 1 at the low
end (1000 Mc)~ Above 1500 Me, no CW oscillation will occur
(see Figure 2-6).
When pure pulse modulation 1s desired at frequencies
below 1500 Mei it 1s necessary to modlf'y t'he pulsing circuit--
at some sacrifice Lri ease of operation or the equipment. The
lOOO-ohm 2-watt oscillator cathode resistor (R124) is replaced
with alOOO-oh.m 25-watt var.1able resistor, and a 20,OOO-ohm
5-watt bleeder resistor 18 connected from +250 volts (rrom the
low-voltage supply) to the oscillator cathode. The leads to
the variable resistor must be kept short because the modulating
pulse 1s applied across it.
In operation, the oscillator is tuned up first on
OW. Then~ with the MODULATOR GAIN control turned fully
coun ter-e-c lock\tvl se , t he MODULATION SELECTOR sw1 tch Ls turned
to PULSE. Observing the indication of the RELATIVE POWER
meter, the oscillator cathode bias should be increased by
increasing the resistance in the cathode circuit te,a point
where the oscillator Just stops oscillating. The pulse drive
should now be increased (by turning the MODULATOR GAIN control
clockwise) until the oscillator starts pu.Ls Lng , The proper
2-7

bias 1s quite critical and will be different for different
operating frequenc1es. Wit.h the bleeder bias arrangement, it
will be found that at the low end of the "/4 mode the oscil-
lator will not pulse on very short pulses. At 300 Me, the
minimum pulse length that will give a good output pulse will
be about 10 ~Bec; at 600 MC
J
the minimum will be about 5 ~sec.
On the 3A / 4 mode, the oscillator will operate on pulses as
short as o.5u.aec , F'lgure 2-7 shows the m1nl.mum pulse length
that can be obtained with this modification.
e. EXTERNAL SQUARE-WAVE INPUT
The modulator tube (VI03) Is not used for aquare-
wave modulation. In8tead~ an external square-wave generator
(auch as the Hewlett-Packard Model 210) is connected to the
panel posts marked SQ. WAVE INPUT .. and the MODU,LA.TION SELECTOR
switch 1s turned to SQ. WAVE. To modulate the oscillator,
about 10 volts at lOOO-ohms lmpedance is required. (NOTEI
The SQ. WAVE INPlJT is in parallel wi th the osc1.11ator cathode
resistor.) If the square-wave source has a low DC resistance,
or if it places a direct voltage across the terminals, the
operating characteristics of the oscillator will be changed.
The DC resistance can be increased by 1.nsertlng an external
r-ee Ls tor- in series wl.tl1 the input ( 1000 ohms will be sufficient),
With the Hewlett-Packard Model 210 square-wave generator, direct
voltages exist between the outer. output ter.m1nals and the center,
If the two outer t.e rm.i na La are used" these direct voltages will
be canceled. It 1s not possible to use a blocking capacitor
in series w1t11 the Lripu t , If a s.mall capacitor 1s used, dif-
ferent1ation or the square wave will take place. A large
capacitor .may cause the oscillator to self-pu.lse.
5• HIGH- VOLT.AGE POWER SUPPLY
The high-voltage power supply consists of one winding
on the power transformer (TIOl), a full-wave type 5R4GY rec-
tifier tube (VI04)~ and associated filter choke and capacitors.
2-8

This circuit supplies 600 volts to the RF oscillator and mod-
ulator plates. Bleeder resistors (R127 and R128) provide a
tap at ~80 volts to supply the screen of the modulator tube
(VI03 ).
6. LOW-VOLTAGE POWER SUPPLY
sq v
The low-voltage power supply consists of a winding
on T10l
fa
full-wave type 5R4GY rectifier tube (VI05), and
associated 1""11 ter choke and capac r tors. The bleeder resist-
ance (R129 and R130) is gr-ounded at the junction. The low-
voltage supply feeds +250 volts to the audio oscillator (VIOl),
the pulse-polarity-changer tube (VI02A), and the modulator
preamplifier (VI02B). In addition, it supplies a negat1ve
biaB to the modulator tube (VI03) when the oscillator 18
pulsed.

SECTION 3
INSTALLATION
1. GENERAL
The equipment is packed in a single unit. The AC
line cord and connectors for the RF output and 'pulse input
are supplied with the equipment.
2. INSPECTION
Before installation, open the access door by
releasing the two fasteners at the rear of the unit and
examine the equipment for possible damage in shipment.
Examine the tubes to see that they are firmly seated in
their respective sockets. Inspect the 2C39A oscillator tUbe
(VI07) (see Figure 2-5). The procedure for removing the
oscillator tube from the cavity unit 1s given in Section 4,
paragraph 5 steps a( 1) and a( 2}] •
The equipment is shipped with the h1gh-rrequency
feedback assembly installed. Note that the other frequency
feedback assemblies are each scr-ewed on holders mounted on
the inside Burface of the access door. The special wrench
for changing the feedback assemblies is similarly mounted.
To change the £eedback aBsembliea, remove the hat assembly
on t.he rear of the cavity un1 t in accordance wi th the 1nstruc-
.t t on s for this pr-o ce dur-e g1 ven in Section 4, paragraph 5.
3. INSTALLATION
The equipment can be operated on a bench or mounted
in a standard rack. To be mounted in a rack, the two handles
must be removed; the unit is then aecu~ed to the rack by four
10-24 machine screws and washers; the access door permits all
3-1

ne ce aea ry adjustments to be made without re.moving the equrp-
ment from the rack.
CAUTION
Before inserting the AC line plug to the
power source
J
make sure that both toggle
switches (Flr~MENT POWER and PLATE POWER)
on the panel are in the OFF (down)position.
NOTE: The Type 12* Power Oscillator
16 designed ~O~ operation on
115 volts, 50 to 60 cps only.
Connection to a power source
of o t.he r voltage or frequency
may r'e su It in damage to the
e qu Lpme nt ,
4. LOAD
Connect a suitable load (preferably not less than
40 feet of RG-21/U or RG-21/AU lossy 50-ohm coaxial cable)
to the R.F. OUTPUT receptacle. If this type of load is not
available} a long length (100 feet or more) of RG-B/u or
RG-9/U cable can be used~ An antenna or other dissipative
load having an SWR of less than 5 in the desired frequency
range can also be used.
CAUTION
Do 110t attempt to operate t ne oscillator
without some RF load connected.
In all cases Where more RF power 1s available than
is needed for a particular application, it is recommended
that a length of lossy 50-ohm cable (RG-21/AU or RG-21/U)
be used between the oscillator and the load. This will
ensure more stable operation when the frequency is changed
over wide limits.
3-2

SECTION 4
OPERATION
1. PRE-OPERATION PROCEDURE
.
a. Turn the MODULATION SELECTOR switch to the C.W.
position.
b. Refer to the calibration curves (Figures 2-2
J
2-3J
and 2-4), and select a PLATE counter reading and a CATHODE
counter reading in the frequency range be1ngused. Turn the
OSCILLATOR TUNING knob until the PLATE counter reading 1s
correct. Then df sengage the plate plunger by pressing 1n on
the knob, and turn it to set the CATHODE counter reading.
c. Reduce the coupling to minimum by turning the
COUPLING knob counterclockwise to a zero read1ng on the
COUPLING counter.
Do not attemot to ooerate the oscillator
without aome RF load connected.
2. STARTING EQUIPMENT
.
a. Turn on the FILAMENT POWER switch. The pilot lamp
above the switch and all vacuum-tube filaments should light.
b. To per~1t the 2C39A (VI07) cathode to reach oper-
ating temperature before plate voltage 1s applied
Ja
time
delay switch is installed (delaYJ approximately 2 minutes),
then turn on the PLATE POWER 5witch. The pilot lamp above
the Bwitch should light. Do not operate the unit if the
blower does not start. When the oscillator is runct1on1ngJ
readings on both the OSCILLATOR GRID meter and t.heOSCILLATOR
PLATE meter will be observed.
4-1