Detailed Equipment Description
Designed and built to the rigid electrical and mechanical specifications of
the U.S. Federal Aviation Administration and certified for use under
extreme environmental conditions, Servo DF systems for both UHF and
VHF, are currently in use in hundreds of locations throughout the world.
These systems, over the past 30 years, have with stood searing
temperatures in deserts of Egypt, hurricanes in the Caribbean and freezing
snow, wind and ice conditions in Alaska and Canada.
Developed in the 1940's by Servo Corporation, the Quasi-
Doppler DF concept simulates the effect of a revolving single
dipole antenna around the circumference of a circle. In this case
the vertically polarized dipoles are electrically commutated to
phase modulate the individually received signals on a sampled
data basis. This phase modulation produces a DF sine wave of
approximately 250 Hz which has a phase relationship
proportional to the angle of arrival of the DF signal. The results
are displayed instantaneously in the digital bearing readout and
ring-of-light display on both the Receiver/Bearing Processor and
the Bearing Display/Control Assembly.
The Receiver/Bearing Processor is installed at the antenna site and
connected via cables to the DF antenna. It is a rack-mounted unit
which contains all the necessary electronic equipment to receive
and process RF signals. For UHF/VHF operation, two of these
devices are required. Although the units look identical they are
specifically tuned for their unique operation.
Received RF signals are converted to a digital output suitable to
drive the Bearing and Ring-of-Lights displays on the front panel of
the unit, and for transmission via a system specified modem over
voice-grade telephone lines to a remote control site equipped with
a Bearing Display/Control Assembly. Controls and displays located on he Bearing Display/Control
Assembly are identical to those on the receiver processor. However, system control is limited to one
site only (either local or remote) as determined by the setting of the LOCAL push-button switch on the
Receiver Processor Assembly. Bearing, frequency and other status information is displayed at both
sites regardless of which has control.
The Bearing Display/Control Unit is installed at the operations site (e.g. Control tower) and connected
via a 4 wire voice grade telephone line circuit to the Receiver/Bearing Processor unit located at the
antenna site. It is a rack-mounted unit which is similar in physical appearance to the Receiver/Bearing
Processor Assembly. The unit contains all circuits necessary to remotely control tuning of the receiver
(located in the Receiver/Bearing Processor Assembly) and to receive and display the receiver channel
frequency as well as status and bearing data through the use of the modem and associated 4-wire
telephone circuit. The Bearing Display/ Control Assembly will display either VHF or UHF signals
depending upon the position of the optional VHF/UHF switch setting on the unit. Except for the
VHF/UHF optional switch and the REMOTE/Local selector switch, all other front panel functions are
the same as those of the Receiver/Bearing Processor Assembly.
Antenna Assembly (About DF Antennas)
The Series 2100 antenna system comes in various options: 16 element VHF, 8 element VHF, 16
element UHF and combination 32 element UHF/VHF assembly.
Servo Corporation of America - All rights reserved
* ServoFlight 2100 Series Direction Finders
* ServoFlight Model 7070M Mobile Direction Finder Station
* ServoSea 2100M Series Marine Direction Finder Systems
* Hardware, spares and software detailed description