February 1967 Electronics World
Wax nostalgic about and learn from the history of early electronics. See articles
Electronics World, published May 1959
- December 1971. All copyrights hereby acknowledged.
Here you are - portable satellite
communications in the mid 1960s per this photo from Electronics World
magazine. It has a unique "cloverleaf" ganged parabolic antenna array with
phasing control. Today, we have "manpack" type systems which use compact
antennas that can be quickly assembled and disassembled in any environment,
along with receivers that have sensitivities much greater than the type shown
here. Software-defined radio (SDR) technology facilitates programmable
modulation and frequency band operation. The Mark V AN/TSC-54 Satellite
Communications Link Terminal featured here operated at 8/7.5 GHz up/down. An
information page for the
AN/TSC-54 can be found on the GlobalSecurity.org website, which includes in
part, "It is completely transportable in two C-130 cargo aircraft." I guess the
definition of "portable" has changed a bit since then.
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 tracking movements.
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
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.
Posted December 8, 2022
(updated from original post on 5/24/2012)