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.

Detailed Equipment Description

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.

Bearing/Display/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.

DF2100 Spares  (www.df2100.com)

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