February 1967 Electronics World
of Contents] People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Electronics World
was published from May 1959 through December 1971. All copyrights are hereby acknowledged.
Electronics World articles.
Here you are - portable satellite communications in the mid
1960s. I guess the definition of "portable" has changed a bit
Portable Satellite Communications Link
When one thinks of a satellite communications station, what
usually comes to mind is a massive parabolic antenna coupled
to a large structure housing a formidable complex of electronics.
During the past couple of years, however, many companies have
succeeded in putting together a highly sophisticated satellite
communicator in a very small package. In many cases, these stations
are capable of being transported by conventional cargo aircraft
to the desired site and then being set up and placed into operation
within a few hours by a crew of only half a dozen men. Such
a typical station is the Mark V AN/TSC-54 Satellite Communications
Link Terminal developed by Radiation Incorporated and shown
in the photo.
The entire system consists of the antenna portion, which
is capable of collapsing down into a small package on its own
trailer; an electronics shelter containing all the operating
equipment; and a lightweight 45-kW, 400-Hz diesel generator.
Total over-all road weight, including crew and sufficient fuel
for 72 hours of operation, is 12 tons, which, if desired, can
be broken down into discrete 3-ton packages for air transport.
Set-up by the six-man crew, time from arrival at the site to
actual communications is two hours.
The unusual-looking antenna has four 10-foot Cassagrain
aluminum reflectors, with the outboard section of each vertical
pair of dishes capable of folding laterally on hinges to make
the antenna transportable.
Each feed emits its energy
through a cone-shaped foam dielectric material extending out
to a small sub-reflector at the end of the feed. Because of
the guiding effect of the foam material, signal losses to the
sub-reflector dish are reduced and over-all antenna efficiency
is improved. Gain is 52 dB at 8 GHz transmit and 51 dB at 7.25
The antenna is a phase-monopulse type using
a special phase shifter which adds and subtracts azimuth and
elevation error signals with the sum signal in such a way as
to permit the use of conical-scan signal processing in the receiver.
These signals are used to drive servo motors which control the
The air-conditioned electronics shelter
can handle multiplexed voice, Teletype, and facsimile, either
directly from on-board equipment or from remote field equipment
linked to the terminal by an appropriate communications system.
The desired combination of signals is achieved using
frequency-division multiplex; this combination is then employed
to frequency modulate a 70-MHz carrier, which is passed to the
electronic equipment in the antenna pedestal base. The signal
is next up-converted to a specific frequency in the 8-GHz band
and amplified to 7 kW by a klystron.
In the receive
mode, the antenna electronics converts the 7.25-GHz input signal
to the i.f. and then passes this down to the remainder of the
receiver in the electronics shelter.
When the equipment is set up and under power, the operator
must then locate a satellite. The problem of locking onto a
satellite is intensified by the relatively narrow beam width
of the antenna (0.3°) and by the fact that the ground terminal's
exact location may be unknown. When the operator presses a button,
the antenna begins to follow a programmed scan pattern very
rapidly. Each satellite is identified by means of a coded beacon
signal. If, during the antenna scan, the ground system intercepts
a satellite beacon, a relay doses and an integrator (position
memory) directs the antenna to the position where the signal
was spotted. If the beacon signal is not detected within two
minutes, the automatic scan is resumed. If it is detected, automatic
tracking begins. The received beacon signature first identifies
the particular satellite; then the ground operator selects the
appropriate frequencies to be used for that satellite and proceeds
to transmit and receive messages.