SECTION II
INSTALLATION/OPERATION
2.1.
Introduction
This section of the technical manual pro-
vides detailed installation procedures and
setup instructions for the GATES Series™
AM transmitters.
Under normal conditions, the GATES Se-
ries™ Transmitters are shipped completely
assembled and ready for installation. How-
ever, if adverse shipping conditions are antici-
pated, certain components may be removed
for transport in which case these components
will be properly identified with appropriate
instructions for reinstalling the components
and making wiring connections.
2.2.
Unpacking
Carefully unpack the transmitter and per-
form a visual inspection to determine that no
apparent damage was incurred during ship-
ment. Retain the shipping materials until it has
been determined that the unit is not damaged.
The contents of the shipment should be as
indicated on the Packing Check List which
accompanies each shipment. If the contents
are incomplete or if the unit is damaged elec-
trically or mechanically, notify the CARRIER
and HARRIS CORPORATION.
2.3.
Returns and Exchanges
Damaged or undamaged equipment should
not be returned unless written approval and a
Return Authorization is received from HARRIS
CORPORATION, Broadcast Transmission Di-
vision. Special shipping instructions and coding
will be provided to assure proper handling.
Complete details regarding circumstances and
reasons for return are to be included in the
request for return. Custom equipment or special
order equipment is not returnable. In those in-
stances where return or exchange of equipment
is at the request of the customer, or convenience
of the customer, a restocking fee will be charged.
All returns will be sent freight prepaid and prop-
erly insured by the customer. When communi-
cating with HARRIS CORPORATION,
Broadcast Transmission Division, specify the
Factory Order Number or Invoice Number.
2.4.
General Installation Information
The GATES Series™ Transmitters have
been designed for rapid installation. In ad-
dition to the 28 inch width by 30 inch depth
of the equipment, a minimum of 24 inches
should be allowed for maintenance access
from both the front and rear of the cabinet.
Signal and power wires can be connected
through several different entries or any de-
sired combination thereof.
The holes for cable entrance are 2 inches
in diameter, and are located at the front and
rear bottom of each side panel. These en-
tries provide a means to enter the equipment
with wires that are then routed into the base
of the equipment.
Input power wires should run to the termi-
nal board installed in the base of the trans-
mitter. Access to this terminal board is
gained by removing the cover plate over the
face of the contactor chassis. The screws
holding the chassis must then be removed
and the chassis pulled forward.
The normal air flow through the transmit-
ter is taken in through the back of the unit
(at the bottom of the cabinet). Maximum
temperature at the base of the transmitter
should not be more than 50°C. The air
moves from the base of the cabinet into the
side panels and into the main enclosure. Air
passes over the heat sink fins in the side
panels and exits through the holes in the top
of the cabinet. This provides efficient chim-
ney action cooling of all the Power Ampli-
fier and Modulator transistors.
The air that enters the main enclosure
passes directly over the components dissi-
pating heat and exhausts through the output
coils and out the top of the transmitter. The
circuit cards and their heat sinks have been
designed to provide a chimney action to the
maximum extent practical.
NOTE
Note that the two blowers have separate
air intakes. One is filtered and the other
is not. The unfiltered side is dedicated to
the PA side wall. No filter is needed be-
cause most of the air passes through the
heat sink fins. A small amount of air is
channeled in the cabinet to flush the PA
Toroids. At approximately one year in-
tervals, the PA heat sink fins should be
inspected and cleaned. They may be re-
moved by removing the 10/32 mounting
screws.
2.4.1.
Power Distribution for Optimum
Transmitter Performance
(This section is applicable to the three
phase GATES FIVE only, as well as other
three phase equipment.)
For many years HARRIS engineers have
recommended that the three phase power
distribution system should be either a
closed delta or WYE configuration to pro-
vide better radio and television transmitter
performance by helping prevent line unbal-
ance. Operation with substantial voltage
unbalance from line to line results in higher
than normal signal-to-noise ratio in the
transmitter output signal, increased three
phase transformer heating, and hot three
phase motors.
2.4.1.1.
Overheating from Line Unbalance
Even a device as simple as a three phase
motor should be operated from a power line
in which the voltage is balanced within 1%. It
takes only a 3.5% line unbalance to produce
a 25% increase above normal temperature. A
5% unbalance will cause destructive tempera-
ture rises of 50% greater than normal!
Similar characteristics can be expected in
the windings of a three phase power trans-
former down inside the cabinet of your trans-
mitter. Transformers and motors can be
designed with extra safety features where ther-
mal rise is limited to acceptable levels; how-
ever, in this case, other transmitter parameters
cannot be made acceptable at a reasonable
cost.
2.4.1.2.
Transmitter Noise Performance
The most difficult parameter to meet with
power line unbalance is transmitter noise
performance. Most large transmitters use
six-phase or twelve-phase high voltage
power supplies. The energy storage capaci-
tors are expensive to install and large stored
energies make destructive faults inevitable.
A good design will have sufficient energy
storage capacitors to meet the specified sig-
nal-to-noise but not much more. When the
equipment is then operated from an unbal-
anced line, the power supply ripple fre-
quency will be twice the line frequency
instead of six to twelve times. It becomes
obvious that it would take three times as
much energy storage to achieve the original
performance goal.
2.4.1.3.
The Causes of Line Unbalance
How does a line unbalance occur? It is a
rare case in which a large commercial
power producer would generate unbalanced
voltage, so we must look elsewhere in the
system. When you have large single phase
power users on a power line this can cause
uneven distribution of the line currents in
the system. Uneven currents through bal-
anced impedances will result in line-to-line
voltage unbalance.
Another likely source of this problem can
come from unbalanced impedances in the
power distribution system. Unbalanced im-
pedance will always be seen when an
“open” delta three phase distribution sys-
tem is used. Transformer design textbooks
Rev. AC: 2/29/00
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