TELE-TECH & - AmericanRadioHistory.Com

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queucy. After consideration of all
the factors involved -including the
use of circular polarization - the
conclusion was reached that other
frequencies offered no real advantage.
Considerable experience
gained at K -band made it seem advisable
to retain this frequency.
In the Engineering Model, the
0.02 -µsec transmitter pulse is produced
by a hard -tube modulator
driving a K -band magnetron. The
peak power of the transmitted pulse
is between 30 and 50 kw. A
hydrogen thyratron pulser is used
to excite the modulator and to
control the pulse duration. The
pulse repetition frequency of 14,400
pps was chosen to give ten pulses
per beamwidth. An investigation
into the use of a hydrogen thyratron
modulator demonstrated that
thyratrons large enough to do the
job would not de- ionize rapidly
enough to operate at this prf. However,
the smaller thyratron used in
the driver circuit has proved very
stable and trouble -free. One advantage
of the short pulse is the fact
that the operation of the magnetron
is isolated from any reflections in
the waveguide that occur more than
8 ft. from the magnetron. Tt is interesting
to realize that this magnetron,
operating at 24,000 mc, generates
480 cycles during a pulse.
The antenna reflector is 12 ft.
wide by 4 ft. high. The horizontal
cross section is parabolic, while the
vertical cross section is shaped to
fan out the elevation beam. The
vertical radiation pattern has a
modified cosecant- squared distribution
extending to 25° below the
peak of the beam. This provides
close -in coverage of the ground -
for instance, giving a minimum
range of 200 ft. when the antenna
is mounted at a height of 100 ft.
A better conception of the electrical
size of the antenna can be had
by considering that 12 feet represents
about 300 wavelengths, or
that an equivalent antenna at S-
band would be almost 100 ft. wide
by 30 ft. high. The tolerance on the
surface of the reflector is quite severe.
In order to be certain of a
sidelobe level of 20 db below the
peak of the beam, it is necessary to
hold the surface to within -*1/64
inch of the desired shape. To keep
the mechanical design of the an-
(Continued on page 184)
Complex Machine Tools
Computer Controlled
A new numerical control device
that operates complex machine
tools by means of digital instructions
which are automatically computed
and recorded on magnetic
tape has been developed by Electronic
Control Systems, Inc., an
affiliate of Stromberg- Carlson and
a subsidiary of General Dynamics
Corp.
This device, called "Digimatic,"
consists of 2 principle parts, a
planning desk, the main part of
which is a high -speed decimal
computer and tape recorder, and
a machine control unit which governs
the operation of the machine
tool from instructions on the magnetic
tape.
A demonstration was given in
which a typical precision cam was
milled from a metal blank, with
the magnetic tape controlling all
the operations of a vertical milling
machine. To prepare for this
demonstration, the dimensions of
the finished part were fed into the
planning desk in sequence,
through a keyboard resembling
that of an adding machine. The
computer converts the dimensional
Transistor Portable
The following information is published as a supplement
to the "1956 Transistor Portable Design" survey which
appeared in the April, 1956, issue of Tele -Tech & ELEC-
TRONIC INDUSTRIES. Since that date, details ou this
receiver have been made available.
ZENITH
Model 500
Dimensions: 53/4
Weight: 19 ozs.
x 31/2 x 11/2 in.
v Nm
data into the proper numerical instructions
and records it in pulse
form on the magnetic tape. The
tape is then played back into the
machine control unit, which controls
the milling machine with
servomotors. Tolerances of .001 in.
or better are obtainable.
One of the big advantages of
"Digimatic" is that any competent
machinist who can read a blueprint
can learn to program the device
with a minimum of training.
Radiosondes Probe
Sky 20 Miles Up
Experimental balloons weighing
less than 2 lbs. but carrying almost
5 lbs. of weather gathering
equipment now are probing areas
more than 20 miles aloft and sending
back hitherto unobtainable information
on atmospheric pressures,
temperatures, and humidity
through a small radio transmitter.
Incorporated in the radiosonde
is a high -altitude hypsometer that
gives accurate pressure measurements
above 85,000 ft. It allows
computation of altitudes and
winds to a much greater degree
than w is possible with standard
radiosondes.
Power Supply: 6 v.
Features: Bat. Max. pwr. out. 180
mw; battery life -approx. 100
hrs.; optional earphone
1 2N94
osc.
bq-.
1 ,,.,.0
2N35
DRIVER
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2UTN3
OPU5T
2X35
OUTPUT
1:;=__11
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rNNNSISIORS
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Tele -Tech &
ELECTRONIC INDUSTRIES
June 1956 For product information, use inquiry card on pages 209 -210. 183