BELL SYSTEM PRACTICES
AT& TCo Standard
SECTION 409-300-102
Issue 4, April 1975
TL-1 MICROWAVE RADIO
TRANSMITTER-RECEIVER BAY
DESCRIPTION
(
CONTENTS
1.
2.
(
PAGE
GENERAL
A.
Receiver Operation
B.
Transmitter Operation
11
C.
Auxiliary Circuits
14
D.
Channel Frequency Considerations
15
3
METER AND CONTROL PANEL
16
A.
Meter Circuit (M3)
18
B.
Meter Circuit (M 1)
19
C.
Klystron Repeller Voltage Control Circuit
and alarm panel or diversity switch panel as
required. At terminals or dropping repeaters, the
outdoor TR cabinet, illustrated in Fig. 1, may also
contain certain multiplex terminal equipment. The
TR packaged for outdoor installation is housed in
an insulated steel cabinet measuring approximately
63 inches high, 47 inches wide, and 19 inches deep.
For indoor installations, a TR bay is available in
7-foot or 9-foot racks as illustrated in Fig. 2. At
a terminal station, one TR bay is required for
nondiversity operation while two TR bays are
needed for a diversity system. At a repeater
station, two TR bays are required for nondiversity
operation while four TR bays are needed for a
diversity system. ·
•This section is reissued to add information
for TL-1 systems that may now be equipped
with either of the following:
1.02
20
D.
Receiver Automatic Frequency Control
Circuit
. . . .
.
20
.Modi.fications to the Meter and Control
Pane..
.
.
22
BAY ARRANGEMENTS AND INTERCONNECTIONS
22
CHANNEL DROPPING AND COMBINING
NETWORKS
24
REFERENCE LIST
25
E.
3.
4.
5.
1.
GENERAL
The transmitter-receiver (TR) bay is the
basic equipment unit of a TL-1 radio system.
It provides the radio transmitting and receiving
equipment for a single 2-way radio channel.
Basically, the TR bay includes a microwave transmitter
and receiver with power supply and auxiliary
equipment. Auxiliary items include an order-wire
1.01
(a) The J99296AA-2, List 3 modulator-preamplifier
unit with the J99296G-2 receiver IF and
baseband unit
(b) The J99296AA-2, List 3 modulator-preamplifier
unit with the J99351E-1 IF amplifier unit
and the J99351J-1 FM receiver unit.•
Equipment for an order-wire and alarm
system is composed of an alarm and control
panel at the alarm center and order-wire and alarm
panels at each radio terminal and repeater station.
One alarm system can serve a maximum of ten
hops for each TL-1 radio system. An additional
alarm system is needed for each additional 2-way
radio system. The following equipment units make
up a complete TR bay:
1.03
(a) Transmitter-receiver panel
(1) Channel dropping and combining networks
(2) Receiver-modulator and preselection
networks
© American Telephone and Telegraph Company, 1975
Printed in U.S.A.
Page 1
SECTION 409-300-102
Fig. 1-J99262A Transmitter-Receiver Cabinet-Door Open View
(3) Receiver IF and baseband unit
(d) Order-wire and alarm panel or diversity
switch panel as required
(4) Transmitter baseband amplifier
(5) Transmitter and monitoring units
(e) Multiplex equipment (when required at
outdoor cabinet installations, terminals, and
dropping repeaters).
(6) Meter and control panel
The TR bay operates from 115-volt 60-Hz
commercial power. An ac distribution circuit
provides convenient outlets where the TL test set
or other electrical equipment may be plugged in
1.04
(b) Power supply
(c) Four 6-volt storage batteries and charger
Page 2
· ISS 4, SECTION 409-300- 102
for maintenanc e testing. A ventilating fan within
the outdoor cabinet operates under the control of
a thermostat to keep the interior cabinet temperature
from rising excessively.
A.
Receiver Operation (Fig. 3 )
• The receiver is equipped with either (a)
the J99296F receiver modulator-p reamplifier
channel assembly (Fig. 4) or (b) the J99296AA,
List 3 modulator- preamplifi er (Fig. 5). If the
receiver is equipped with (a), refer to 1.06 through
1.10. If the receiver is equipped with (b), refer
to 1.06 through 1.08 and 1.11 through 1.14.
1.05
The three IF and baseband units available
in a TL-1 system and described in this section
are as follows:
1.06
(a) J99262G receiver IF and baseband
unit-parag raph 1.15.
(b) J99296G IF and baseband unit-parag raph
1.21, Fig. 6 and 7
(c) J99351E-1 IF amplifier unit with the J99351J-1
FM receiver unit-parag raph 1.23, Fig. 8
and 9.•
The incoming RF signal is received from an
adjacent radio station in the circular feed
of a parabolic antenna. This complex RF signal
may contain from one to six radio channels on
one or two polarization s. The signal is carried by
the circular antenna waveguide to a polarization
separation network or a round-to-r ectangular
transition , depending upon whether the signal
contains one or two polarizatio ns. With two
polarizations, the separation network separates the
vertically and horizontally polarized frequencies
and launches them into rectangular waveguides . In
the case of a single polarization , a transition is
used to connect from circular to rectangula r
waveguide . The channels , now grouped by
polarizatio ns, are transmitte d by rectangula r
waveguide runs to the TR bays. A maximum of
three transmitter s and receivers are fed by one
waveguide run. The transmitted RF signals have
the shorter path to the antenna and are coupled
to it by channel dropping and combining networks.
These networks are also used to connect the
microwave receivers to the main waveguide run.
1.07
Fig. 2-J99262B Transmitter- Receiver Rack- Mounted,
7-Foot Bay
Page 3
SECTION
409~300-1 02
(
CHANNEL
DROPPING
NETWORK
,.!.~~-;BP:-;F;;i:IL::iiTE;Rf----~~----i
ISOLATOR
1-------(~-~,...__------1
~r
r~
~
~
I I
TO
RECEIVER
POLARIZER
1-------1---!
(
TO OPPOSITELY
POLARIZED
TRANSMITTERS AND
RECEIVERS
TO TRANSMITTERS
18-0B
VOLTAGE
GAIN
(
+29 OB
+28 DB
AGC VOLTAGE
-1 OB
+2 DB
+49 DB
(25 MV/MHZl
DC
fRF t70 MHZ
DC
AFC
NORMAL /
TYPICAL POWER LEVELS
40-DB FADE
DBM/
DBM
(
Fig. 3-J99262G Receiver-Block Diagram
In a particular bay, a channel dropping
network selects its designated RF channel
from the other channels and passes it on to its
receiver. The remaining RF channels pass through
the network. At the end of the waveguide run,
selection is not required since only one RF channel
is present, the others having been dropped. It is,
therefore, applied directly to its receiver.
1.08
As shown in Fig. 3, an isolator is located
between the channel dropping and channel
combining networks. Its function is to prevent
beat-oscillator leakage from passing through the
polarization separation network and interfering with
other receivers. The isolator, in general, is installed
only when four or more bays operate off one
antenna.
1.09
The selected signal enters the receiver
through a bandpass image rejection filter
and a waveguide tuner to a balanced diode modulator.
The modulator-preamplifier contains a balanced
crystal converter and a transistor preamplifier.
1.10
Page 4
The converter portion consists of a waveguide
hybrid which mounts the input waveguide section
and a waveguide attenuator through which the BO
signal is introduced. The output branches contain
matched crystal diodes. A eoaxial jack is provided
at the output of the preamplifier for a connection
to the IF and baseband unit. Coaxial jacks are
also provided for connections to the receiver control
unit to permit reading the modulator crystal currents
and for the power supply connection to the
preamplifier. The complete receiver modulatorpreamplifier channel assembly is shown in Fig. 4.
This assembly is coded as the J99296F
modulator-preamplifier channel assembly and must
be tested and adjusted as a complete unit. The
List 1 unit is rated "Manufacture Discontinue,"
(MD).
When a receiver is equipped with the
redesigned modulator-preamplifier, the channel
assembly consists of a bandpass filter, waveguide
ferrite isolator, and a J99296AA, List 3
modulator-preamplifier (Fig. 5). The isolator replaces
1.11
ISS 4, SECTION 409-300-102
Fig. 4-J99296F Modulator- Preamplifie r Channel
Assembly With List 1 Modulator-P reamplifier
Fig. 5-J99296A A, List 3 Modulator-P reamplifier With
Associated 9A Isolator and 1307 Filter
the frequency- sensitive waveguide tuner. The
modulator-p reamplifier contains a balanced crystal
converter and a transistor preamplifier. A monitor
jack has been added providing a bridged input at
the interface of the modulator and first IF amplifier
stage.
from the beat oscillator to produce an intermediat e
frequency centered at 70 MHz. The IF output of
the modulator is connected directly to the input
of a low-noise preamplifier . The beat oscillator is
under the control of the AFC circuitry, and its
frequency may be higher or lower than the incoming
signal frequency depending upon the channel number.
Table A lists the channel numbers, the 1307-type
filter and 1402-type network codes, and the incoming
signal and BO frequencies.
The J99296AA modulator-p reamplifier is a
balanced crystal converter, or mixer, which
combines the incoming RF signal with the output
1.12
Page 5
$ECTIO._ .:4()9-300-192
TABLE A
NORMAL FREQUENCY PLAN
FREQUENCY
1307-TVPE FILTER
AND
1402-TVPE NElWORK
CODES
CHANNEL NUMBER
Page 6
GHz
OLD
NEW
1
1
2
2
A
B
A
B
p
J
p
J
B
T
G
AD
10.755
11.405
10.955
11.685
10.825
11.335
11.025
11.615
3
3
4
4
A
B
A
B
p
J
p
J
H
10.995
11.645
10.715
11.445
11.065
11.575
10.785
. 11.375
5
5
6
6
A
B
A
B
p
J
p
J
M
R
E
11.155
11.325
10.875
11.605
11.085
11.255
10.805
11.535
7
7
8
8
A
B
A
B
p
J
p
J
F
AA
L
10.915
11.565
11.115
11.365
10.845
11.495
11.045
11.295
9
9
10
10
A
B
A
B
p
J
p
J
K
N
11.075
11.245
10.795
11.525
11.145
11.315
10.865
11.595
11
11
12
12
A
B
A
B
p
J
p
J
D
10.835
11.485
11.035
11.283
10.905
11.555
11.105
11.355
The staggered frequency plan is intended
primarily for use on converging or crossing
routes in congested areas. It is not recommended
to be used on the same antenna systems as the
normal frequency plan. If it is necessary to do
so, very careful consideration must be given to
interference problems caused by adjacent channels
and beat oscillator frequencies. The added frequencies
are spaced 20 MHz from and midway between the
existing channels. The frequencies start at 10.735
· GHz and extend to 11.665 GHz as shown in Table B.
1.13
BEAT
OSCILLATOR
SIGN.AL
AC
A
u
AB
s
c
y
w
J
p
The output of the beat oscillator is fed into
the E-plane junction at the relatively high
level of approximately 0 dBm which is controlled
by the 28A waveguide attenuator. The incoming
carrier signal splits at the junction and is impressed
on diodes CR1 and CR2 in opposite phase. Since
the .diodes are mounted in the waveguide with
opposite polarities, they will conduct simultaneously,
and a balanced switching action will be produced
within the hybrid. Because of the symmetry of
the hybrid, none of the BO output will appear at
1.14
(
(
ISS 4, SECTION 409-300-102
TABLE B
STAGGERED FREQUENC Y PLAN
FREQUENCY
(
CHANNEL NUMBER
OLD
(
1
1
2
2
3
3
4
4
(
1307-TVPE FILTER
AND
1402-TVPE NETWORK
CODES
c
D
c
D
c
D
c
D
c
5
5
6
6
D
7
7
8
8
D
9
9
10
10
11
11
12
12
c
D
c
c
D
c
D
c
D
c
D
c
D
BEAT
OSCILLATOR
SIGNAL
NEW
GHz
E
D
E
D
AF
BA
AL
BH
10.775
11.385
10.975
11.665
10.845
11.315
11.045
11.595
E
D
E
D
AM
BG
AE
BB
11.015
11.625
10.735
11.425
11.085
11.555
10.805
11.355
E
D
E
D
AS
AW
AJ
BF
11.175
11.305
10.895
11.585
11.105
11.375
10.825
11.515
E
D
E
D
AK
BE
AR
AY
10.935
11.545
11.135
11.345
10.865
11.615
11.065
11.275
E
D
E
D
AT
AG
BD
11.095
11.225
10.815
11.505
11.025
11.295
10.885
11.575
E
D
E
D
AH
BC
AN
AU
10.855
11.465
11.055
11.265
10.785
11.535
11.125
11.335
the signal input port of the hybrid, provided the
diodes are perfectly matched. The signal at the
H-plane junction divides in phase between the two
hybrid arms containing CRl and CR2. These signals
are impressed on the diodes which are varying in
impedance at the BO frequency and, as a result,
frequency combinations of signal and BO frequencies
are produced. Of all the possible combinatio ns,
only the difference and image frequencies are of
significance. All the other frequency combinations
are either at too high a frequency or too low a
level to have any effect on the operation of the
AP
modulator . The difference frequency is the
intermediat e frequency of 70 MHz which is obtained
by paralleling in phase the outputs of the two
diodes. This signal is connected directly to the IF
preamplifier.
J99262G Receiver IF and Baseband Unit
1.15
The IF signal is first amplified in a multistage
wideband amplifier composed of amplifier
sections A., B, and C. These sections introduce
very little amplitude and phase distortion in the
Page 7
sr;cno._. .499~-102
signal because their passband is very broad in
comparison to that of the overall IF amplifier.
Since the amplifier is fully transistorized, automatic
gain control (AGC) is performed with two variolossers
located between amplifiers A, B, and C. These
devices are made up of biased diodes and present
an insertion loss that varies with the received
signal level. Their action causes the IF signal at
the output of the second variolosser to vary only
1 dB over a 40-dB range of RF input power.
activated by monitoring the de biasing voltage of
the AGC amplifier which is proportional to the RF
input signal.
The baseband signal at the output jack now
passes through the diversity switch and/ or
the order-wire and alarm and is then applied to
either multiplex equipment or a radio transmitter.
1.20
J99296G IF and Baseband Unit
Complete IF bandpass shaping occurs in the
IF filter following amplifier section C. This
filter is also designed to equalize the small
transmission deviations existing in the amplifier.
The IF signal is boosted an additional 49 dB in
amplifier section D which drives the limiter and
the AGC circuits. For AGC purposes, a portion
of the IF signal is diode detected, producing direct
current which is amplified, and used to control
the bias on the variolosser diodes.
1.16
After limiting, the IF signal is detected in
a wideband frequency discriminator. The
recovered baseband signal is then amplified in a
baseband amplifier and brought out to a 75-ohm
jack for application to multiplex terminal or radio
transmitting equipment.
1.17
To compensate for frequency drifts in the
transmitting and receiving klystrons, the
frequency of the BO is controlled automatically,
thereby keeping the IF signal centered at 70 MHz.
A de input signal for the automatic frequency
control (AFC) is derived from the discriminator
output. Polarized direct current is present at this
point when the IF is other than 70 MHz. A de
signal at this point passes through a transistorized
de amplifier, is amplified in a magnetic amplifier,
and then applied to the BO repeller to correct its
frequency. The frequency will change in the
direction that tends to null the discriminator de
output and therefore a fixed 70 MHz is maintained.
In addition to AFC, the BO klystron is
frequency-stabilized by a temperature control system
that is described in 1.28.
•The IF and baseband unit (J99296G), Fig. 6
and 7, is a transistorized plug-in component
of the RF panel and provides an unbalanced baseband
output signal from an unbalanced 70-MHz IF input
signal. It includes the following.
1.21
(a) Amplifiers to raise the level of the 70-MHz
frequency-modulated IF signal supplied to
the unit from the modulator-preamplifier.
(b) Variolossers which serve as part of the
AGC circuit to hold the IF output approximately
constant with fading of the input signal.
(c) An IF bandpass filter to suppress unwanted
frequency components outside the 60- to
80-MHz IF band.
1.18
A squelch circuit is incorporated in the
receiver. This circuit cuts off the baseband
amplifier when the RF carrier is reduced to or
beyond a specific value by a fade or equipment
failure. Excess noise is thus stopped before it
can enter multiplex equipment where it could mix
with good working circuits. The squelch circuit is
1.19
Page 8
(
(d) A limiter to remove amplitude modulation
from the frequency-modulated IF signal
before it is supplied to the discriminator.
(e) A discriminator to recover the baseband
information from the frequency-modulated
IF signal.
(f)
A baseband amplifier to raise the signal to
the level required for the connecting circuits.
(g) An AFC de amplifier to transmit the
differential output of the discriminator to
the magnetic amplifier located on the receiver
control unit. The output of the magnetic amplifier
is applied to the BO repeller in a direction to
maintain a constant 70-MHz intermediate frequency.
(h) An AGC detector and amplifier which, in
conjunction with the variolossers listed above,
serve to hold the limiter input approximately
constant.
(
ISS 4, SECTION 409-300-102
(i)
A diversity drive circuit which provides a
control voltage to operate the diversity switch
circuit.
(j)
A squelch circuit under control of the AGC
circuit to mute the output of the baseband
amplifier at a specified depth of fade. Simultaneously,
the automatic frequency control loop is effectively
opened to remove control and allow the beat
oscillator to return to its approximate ly correct
nominal operating frequency. With the AFC
circuit disabled, the beat oscillator is prevented
from locking at a new frequency under the
influence of an adjacent channel carrier or
extraneous carrier signal.
..
•
1.22
The IF and baseband unit includes panel
adjustments and jacks as follows.
(a) The LIM IN control provides a means for
adjusting the limiter input level.
(b) The AFC ZERO control provides a means
for adjusting the differential voltage of the
AFC circuit to zero when the IF signal is 70
MHz.
(c) The RCVR GAIN control is used to adjust
the baseband signal output power.
(d) The IF GAIN control, provided only on the
J99296G, L4 and L4A units, provides a means
for adjusting the squelch point to correspond
with a specific 70-MHz input level. This control
is located on the back of the unit and is adjusted
at the factory. However, it may be adjusted in
the field on an out-of-service basis by removing
the unit, making the adjustment, and replacing
the unit as required, until the proper squelch
point is established.
(e) The RCVR OUT jack provides the means
for connecting the baseband output signal
to the connecting circuits.
RCVR
IF & BB
S097159·02
J99296G·2l4
UM•v
.J.L
(f) The LIM IN ( +) and (-) jacks provide a
means for indirectly monitoring the limiter
input level.
(g) The AGC ( +) and (-) jacks provide a means
for monitoring the AGC voltage other than
the means provided by the meter AGC position.
The voltage of the AGC (-) jack with respect
to ground is approxima tely 6 volts and the
difference between the two jacks ( +) and (-)
ranges from 0 to 1 volt depending on received
signal strength.
(h) The IF IN jack, located on the bottom of
the unit, provides the means of supplying
the IF signal from the modulator- preamplife r
unit to the IF amplifier.
(i)
Fig. 6-J99296G IF and Baseband Unit
The RCVR OUT jack, located on the front
of the unit near the top, provides the means
for s upplying the baseband output to the
connecting circuits.
(j)
The IF MON jack, located on the front of
the unit near the bottom may be used for
Page 9
SECTION 409·300-1i»2
. TO 1402
NETWORK
(',
IF MON
(OOBM)
IF/BB UNIT
(
(
MOD
PATCH
CORD
INPUT
AMPL
)
88
OUTPUT
AMPL
BPF
AND
ATT
28A
WAVEGUIDE
ATT
AMPL
LIM
DISC
RCVR
OUT
TO DIV
1----+--+--+-7 SWITCH
RCVR
AFC AMPL
(
Fig. 7-Receiver Equipped With J99296G IF and Baseband Unit-Block Diagram
test purposes or to drive an IF repeater for
possible connections to a TD-2 radio.
J99351E-1 IF Amplifier and J99351J-1 FM Receiver
Arrangement
The IF amplifier and FM receiver arrangement
(Fig. 8 and 9) is comprised of three individual
units consisting of a 1075A filter, IF amplifier
(J99351E), and FM receiver (J99351J) packaged
together as a plug-in arrangement to replace the
receiver IF and baseband unit (J99296G). The
70-MHz FM signal from the modulator-preamplifier
unit is supplied through the 1075A filter to the IF
amplifier and FM receiver units which, together,
recover the baseband information from the IF signal.
The baseband signal is amplified and supplied as
an unbalanced output to the connecting circuits.
The arrangement includes the following.
1.23
Page 10
(a) Amplifiers which raise the level of the
70-MHz frequency-modulated IF signal
supplied through the 107 5 filter from the
modulator-preamplifier unit.
(b) Variolossers which hold the IF output level
essentially constant with fading of the input
signal.
(c) A limiter which removes amplitude modulation
from the IF signal before it is supplied to
the discriminator.
(d) A discriminator which recovers the baseband
information from the frequency-modulated
IF signal.
(e) A baseband amplifier which raises the signal
to the level required for the connecting
circuits.
( ....
·
ISS 4, SECTION 409-300-102
(
(
An AFC de amplifier which transmits the
differential output voltage derived from the
discrimin ator to the magnetic amplifier located
on the receiver control unit. The output of the
magnetic amplifier is applied to the BO repeller
to maintain a constant 70-MHz intermed iate
frequency.
(f)
unit to the RCVR IN jack of the FM receiver
unit.
(c) The IF MON jack provides a means for
monitoring or measurin g the 70-MHz output
of the IF amplifier unit. The level at this point
is nominally 0 dBm and is normally terminate d
by a 469A plug (75 ohms).
(g) An AGC detector and de amplifier which
hold the limiter input constant.
(d) The AGC control provides a means for setting
the IF output level applied to the limiter to
-7 dBm for a prescribed IF input level.
(h) A squelch amplifier which monitors the
output of the AGC amplifier, compares it
with a fixed reference voltage, and when a
predeterm ined level is reached, squelches the
baseband amplifier output, and activates the
AFC squelch relay which prevents the beat
oscillator from locking under control of an adjacent
channel carrier or extraneou s carrier signal.
(e) The SQCH control provides a means for
adjusting the squelch .point to correspon d
with a specific 70-MHz IF input signal level.
FM Receiver (J99351J)
(a) The RCVR IN jack provides a coaxial
connection for patching the output of the IF
amplifier unit into the input of the receiver unit.
(i)
A diversity AGC amplifier which converts
the polarity and sets the gain of an input
from the AGC amplifier to operate a diversity
switch.
(j)
(
(b) The RCVR OUT jack provides the means
for supplying the baseband signal to the
connecting circuits.
The IF filter (1075A) and associated cords
for the IF amplifier and FM receiver units.
(c) The BB GAIN control provides a means for
setting the level of the baseband signal
supplied to the connecting circuits.
The IF amplifier and FM receiver arrangem ent
includes cords, adjustme nts, and jacks as
follows.
1.24
(d) The AFC ZERO control provides the means
for adjusting the differenti al voltage of the
AFC circuit to zero when the IF signal is 70
MHz.
1075A Filter
(a) The IF input jack, designate d either Jl or
J2 provides the coaxial connection from the
modulator-preamplifier unit. This jack is located
on the rear of the filter enclosure.
(b) The IF output jack, designate d either Jl or
J2, provides the coaxial connection from the
output of the filter to the input of the IF amplifier
unit. This jack is located on the rear of the
filter enclosure.
IF Amplifie r (J9935JE)
Cords
Coaxial cords with connector s provide the means
for interconnecting the filter, IF amplifier, and FM
receiver units. A cord is also provided which
adapts the RCVR OUT jack to the plug already
provided in the RF panel .•
B.
Transmitter Operation (Fig. 10)
(a) The IF IN jack provides the means for
connecting the output of the 1075A filter to
the input circuits of the unit. This jack is
located on the rear panel of the unit.
The transmi tting circuit produce s a
frequency -modulate d signal in the 11-GHz
band at a power level of approxim ately 100
milliwatts . It is designed to accept a baseband
input signal from a 75-ohm unbalance d source.
(b) The IF OUT jack provides a coaxial connection
1.26
1.25
\.
for patching the IF output of the IF amplifier
The baseband amplifier is a 3-stage transistorized
feedback amplifier with a voltage gain of
Page 11
SECTION 409-300-102
(
840881700 CABLE I TL-21
OR 840881726 CABLE ITM-11
1075A FILTER
\
IF AMPLIFIER UNIT
IJ99351E1
Fig. 8-IF Amplifier and FM Receive r A rran gement Consisting of 1075A Filter, J99351 E IF Amplifie r Unit,
J99351J FM Receiver, and Associated Cables
approximately 28 dB and a bandwidth which is
essentially flat from 200 Hz to 6 MHz. Here the
baseband signal is amplified with a minimum of
distortion and applied to the transmitting klystron
repeller through a short length of wire. The varying
amplified baseband signal linearly modulates the
klystron-generated frequency. This FM signal is
fed through a 1B isolator which has a forward loss
of about 1 dB. The reverse loss of the isolator is
approximately 55 dB and it, therefore, minimizes
klystron frequency pulling caused by antenna and
waveguide reflections. The RF signal then passes
through a double directional coupler and on to the
channel combining network. The two couplers are
used to provide a frequency and power output
indication. In the first coupler, the RF signal, 20
dB down from that in the through arm, is passed
through AT2 and a very narrow bandpass filter
tuned to the assigned transmitter frequency. The
attenuator and filter, in conjunction with a meter
on the meter and control panel, are used in adjusting
the transmitter frequency and deviation. The RF
signal in this leg is converted to direct current in
DET 2, a diode detector, and then applied to M1
which gives a peak indication when the frequency
Page 12
is properly adjusted. The second coupler of DC 1
also contains an RF signal that is 20 dB down from
that in the through arm. This signal is converted
in DET 1 to direct current which gives a power
output indication on meter M3.
At the combining network, the transmitter
signal is inserted in the main waveguide line
and propagated toward the antenna along with the
channels from other transmitters. Horizontally
and vertically polarized signals are fed to the
circular antenna waveguide feed through the
polarization combining network. The composite
signal is then propagated to the next station by
the antenna.
1.27
The transmitting and receiving klystrons are
stabilized against frequency drift by maintaining
them at a constant temperature. This is performed
by means of a vapor-phase cooling system. This
system is composed of a small boiler located
between the two klystrons, a condensing system,
a tube that interconnects a boiler and condenser,
and a rubber bladder. A fluorochemical liquid,
having a boiling temperature of approximately
1.28
r
--
,~-
(
\__
TO 1402
TO 1402
NETWORK
NETWORK
--
~-
1
9A
ISOLATOR
If"
MON
(0 DBM)
If" AMPLIF"IER
J99351E
PATCH
CORD
'
J;;;2
_,
1075A F"ILTER
(IF" B.P.
f"ILTER)
If" AMPL
AGC
AMPL
FM RECEIVER
J99351J
LIMITER
DISCRIMINATOR
BASEBAND
AMPL
RCVR OUT
Af"C
AMPL
SQUELCH
AMPL
TO Af"C
SQUELCH
iii
DIVERSITY
AGC
1------ ,------- ------+ -------- -----'-'- < TO
'l
CD
w
"'
!"
"'m...
n
6
z
80 KLYSTRON
Ia
I
I
DIVERSITY
SWITCH
Fig. 9-Receiver Equipped With J99351E IF Amplifier Unit, J9935U FM Receiver, and 1075A Filter-Block
Diagram
Is
SECTION 409-300-102
TO TRANSMITTERS
AND RECEIVERS O N + - - - - - - - - - - - - - ,
OPPOSITE 'POLARIZATION
(
-14 DBM
(-IS. 5 DBVI FOR ±4MC DEVIATION
I
FROM
TRAN.SMITTERS
DC
FREQUENCY
AND DEVIATION
MONITOR
'f
Ml
(
CHANNEL
COMBINING
NETWORKS
_.,.__.-oo ~I
TO RECEIVERS
POWER
MONITOR
M3
Fig. 10-Transmitter-Biock Diagram
214~F, is contained within the system. In that
boiler, heat energy generated in the klystrons boils
and vaporizes the fluorochemical. The vapor travels
through the tube up to the condenser where it
cools, condenses, and then runs back to the boiler
by gravity feed. Converting the fluorochemical
from the liquid to vapor state occurs at constant
temperature and continuously draws heat from
the. klystrons, thereby stabilizing the klystron
t;em,perature. Temperature variations in the TR
bay environment cause minimum temperature change
to the klystrons because an appropriate change in
the rate of vaporization and condensation will then
take place.
C.
1.29
Auxiliary Circuits
The diversity switch unit continually monitors
the two channels of a diversity pair and
Page 14
selects the better channel to deliver the baseband
output signal, as illustrated in Fig. 11. Baseband
switching occurs in the K4 relay controlled by the
logic circuit which secures information on the quality
of the radio channels from a fade comparator and
two pilot monitors. The pilot monitors are bridged
across the receiver outputs and detect the presence
and absence of a 2600-Hz continuity tone. This
tone is applied to the radio at a near-end terminal
for alarm signaling purposes and passes through
every radio bay and station in a radio system.
Absence of this tone on one channel of a diversity
pair indicates a failure in that channel, and the
switching circuit selects the baseband signal from
the good channel. When pilot tones are received
by both pilot monitors, the fade comparator
determines which receiver supplies the baseband.
Transmission quality is compared here by finding
which channel has a stronger RF input signal and,
(
ISS 4, SECTION 409-300-1 02
(
therefore, less noise. The better channel is selected
on the basis of an AGC voltage comparison made
in the fade comparato r.
D.
The TL-1 radio system uses the 11-GHz
frequency band between 10.7 and 11.7 GHz.
This band is divided into 24 channels with 40-MHz
separatio n between midchann el frequenci es. On
any one system hop, alternate channels (12 total)
having 80-MHz separation are used. These channels
are alternatel y polarized, giving 160-MHz separation
between adjacent channels of the same polarization.
1.32
Order-wir e and alarm signals are transmitte d
over the radio in the voice-frequency portion
of the baseband spectrum. As shown in Fig. 11,
these signals are separated from the multiplex at
each station with split-apar t filters and fed to the
order-wi re and alarm circuits. The complete
baseband signal reappears at the output of a second
split-apar t filter which is turned around to combine.
The composi te signal is applied to the two
transmitt ers through a split pad. In nondiversity
systems, the same order-wire and alarm arrangeme nts
are used, but one of the split pad outputs is
terminate d since only one transmitt er is utilized.
1.30
(
Channel Frequency Considera tions
The adjacent radio paths use the alternate
12 channels, resulting in 40-MHz separation
between channels on opposite sides of a repeater
station. To provide adequate separatio n between
transmitti ng and receiving frequenci es at any one
station, the upper half of the frequency band is
allocated to transmitt ing when the lower half is
receiving. Since transmitt ers work into receivers
of the same frequencies, alternate repeater stations
will receive in the upper half and transmit in the
lower half of the frequency band (Fig. 12). In
addition, the separation between the two channels
adjacent to midband is 90 MHz instead of 40 MHz.
This fulfills the requirem ent for a minimum
1.33
The design of the TL-1, operating in the
11-GHz band and the TM-1 operating in the
6-GHz band, has been coordinat ed to assure a
convenien t combinati on of the two systems in a
crossband diversity system. The six 2-way broadband
TL-1 channels are available for inband or crossband
diversity operation.
1.31
MX DROP
AND ADD
,---- ----- ----- ----- --l
I
I
I
I
I
I
I
I
I
AGC
AGC
I
I
I
COMPARATOR
LOGIC
CIRCUIT
(CONTROLS K4)
I
I
I
I
I
I
I
\.
I
I
I
I
MX THRU
0 WAND RELAY
CIRCUITS
I
I
L _____ _ ~v_:_R~T2:_ s~~H_U~T- _ _ _ _ _ _ -~
Fig. 11-Transm itter-Rece iver Auxiliary Circuits-B lock Diagram
Page 15
--~
SECTION 409-300-102
separation of 130 MHz (90 + 40) between any
transmitting and receiving channel combined at
one antenna.
REGULAR
In order to implement these generalized
requirements, a channel assignment and
frequency allocation plan has been established.
For this plan, the 12 channels in the lower half
of the total frequency band are designated group
A (old designation) or group P (new designation).
The channels are numbered 1A/P to 12A/P in
accordance with a definite numerical plan which
dictates the system growth. The 12 channels in
the upper half of the total frequency band are
designated group B (old designation) or group J
(new designation) and are numbered 1B/J to 12B/J.
The following explains the plan.
1.34
(
(a) Channels (6 maximum) transmitting north
or east have odd numbers. Channels (6
maximum) transmitting south or west have even
numbers.
(b) All channels transmitting in one direction
on a specific hop are designated AlP; in
the opposite direction, B/J; and on adjacent hops
this is reversed.
(c) Channels are assigned and installed in numerical
order within a directional group beginning
with channel 1 or 2 (Fig. 13). Channels 1, 2,
3, and 4 are contained in the first diversity
switching group; channels 5, 6, 7, and 8 in the
second diversity group; and channels 9, 10, 11,
and 12 in the last diversity switching group.
NOTES:
!. A-OLD CHANNEL
DESIGNATIONS.
P-NEW CHANNEL
DESIGNATIONS.
2. B-OLD CHANNEL
DESIGNATIONS.
3. J- NEW CHANNEL
DESIGNATIONS.
(
(d) ·In this plan, a single baseband signal (ignoring
diversity switching) retains its basic number
through a system, but changes its letter designation
on adjacent hops. In addition, the polarization
of a specific channel is shifted every third hop
to minimize the adverse effects of overreach
interference.
(e) The two channels within a protection group
are oppositely polarized. This will permit
maintenance and growth with a minimum
interruption of service.
2.
(.
METER AND CONTROL PANEL
The meter and control panel, illustrated in
Fig. 14 and 15, is a subassembly of the
transmitter-receiver panel that provides means for·
2.01
Page 16
Fig. 12-The 11-GH:r: Frequency Plan-Block Diagram
ISS 4, SECTION 409,..300-102
11-GHZ PREFERRED GROWTH PLAN
(
CHANNEL
DESIGNATION
(
NEW
OLD
2J
?B
3J
3B
6J
(
(
6B
7J
7B
IOJ
lOB
IIJ
liB
4J
4B
IJ
IB
SJ
88
5J
58
12J
128
9J
98
5P
5A
8P
8A
CHANNEL
DESIGNATION
GROWTH STAGE
I
·~.
3
4
5
6
• • • • • •
• • •
• •
• • • • •
• • • •
•
• • •
• • • • • •
• • • • •
• •
•
• • • •
• •
• • • • •
• • • •
9P
9A
12P
12A
•
3P
3A
2P
2A
• • •
• • • • • •
• • • • •
7P
6P
•
•
TM-1 PREFERRED GROWTH PLAN
.
7A
6A
liP
IIA
lOP
lOA
IP
lA
4P
4A
• •
•
• • • •
• • • • • •
• • •
DENOTES CHANNEL EQUIPPED
NEW
OLD.
GROWTH STAGE
. I
2
3
4
5
6
7
8
•
•
28U
288
28C
28A
27U
278
27C
27A
26U
26B
26C
26A
25U
258
25C
25A
24U
248
24C
24A
23U
238
• •
23C
23A
• •
22U
228
22C
22A
21U
218
21C
21A
IBU
188
ISC
ISA
17U
178
17C
17A
16U
168
16C
16A
15U
158
15C
15A
14U
148
14C
14A
13U
138
13C
13A
12U
128
12C
12A
IIU
liB
IIC
I lA
• • • • •
• • • • •
• • • •
• • • •
• • •
• • •
• • •
• • •
• • • •
• • • •
• •
• •
• • • •
• • • •
• • • •
• • • •
• • • •
• • •· •
• •
• •
• • • • •
• • • • •
• • •
• • •
•
•
• • • •
• • • •
•
•
• • •
• • •
• • •
• • •
• • •
• • •
• •
• •
• • •
• • •
• • •
• • •
• • •
• • •
Fig. 13-The TM-1/11-GH z Preferred Channel Grawth Plan for Crossband Diversity Application -Chart
Page 17
SECTION 409-300- 102
making certain maintenance tests and adjustments
and for monitoring various parameters within the
TR bay without disturbing service. The major
testing facilities contained in this panel are as
follows:
(a) A meter to measure operating voltages and
currents and transmitter power output
(b) A meter used for monitoring and adjusting
receiver AFC (panel marked IF) and transmitter
(panel marked XMTR) frequency and deviation.
The control panel components are assembled
on an aluminum panel, and meters and
operating controls are accessible from the front.
Connections to the panel are made through two
plugs, making it readily removable for servicing.
Overall dimensions of the assembly are approximately
4 inches wide, 14 inches high, and 3 inches deep.
2.02
FREO
L
A schematic of the control panel is shown
in Fig. 24. For descriptive purposes, this
circuit is divided into four parts which are described
in the following paragraphs. •I n addition, the
modifications to the meter and control panels of
some TL-1 systems are described, beginning with
paragraph 2.13 .•
2.03
A.
Meter Circuit (M3)
BO
RPLR
This meter, in conjunction with switch S6,
is used to measure power supply voltages,
various currents, and transmitter power. These
measured parameters are as illustrated in Table C.
2.04
The supply voltages are measured by switching
the meter and series resistor R37, which
results in a 30-volt full-scale voltmeter, to the
appropriate resistor or combination of resistors in
the bleeder string consisting of R28, R29, R31,
R32, and R33. This circuit is shown in simplified
form in Fig. 16. The regulated 20-volt supply,
27.6-volt battery voltage, and AFC amplifier voltage
output are measured directly with the meter and
R37. The -200 volt supply measurement is actually
a measure of the difference between the -400 volts
and what is designated as -600 on the circuit
schematic. Minus 600 volts is obtained in the
power supply by floating -200 volts below the -400
volts resulting in -600 volts to ground.
2.05
2.06
The 1A modulator diode CRl and CR2
currents are measured directly with M3 used
Page 18
,_--...........
,.~'\
~' /
(
I
)
AGC
CR2
\
Cl
\:Fe-/
11- -2o
NOR
TST
J /
PWR
~
-CATHj
-oFF
I
BAT
LIN
CATH RF
"
\
-400
-200
J2+
AFC
FIL ACT
OFF
XMTR
ON
80
REMOVE KlYSTRON FUSE
BEFORE
REMOVING OR
INSTALLING PANEl
Fig. 14-J99262K Meter and Control Panel
ISS 4, SECTION 409-300-102
TABLE C
S6 SWITCH
POSITION
1
2
3
4
-20 volt supply voltage
Receiver AFC vo ltage
CR1 converter diode current
CR2 converter diode current
5
6
Receiver AGC vo ltage
BO klystron cathode current
RF power output
Transmitter klystron cathod
current
7
8
R35
FREQ
9
10
11
12
n-
®
...
lll
Fig. 15-J99262K Meter and Control Panel Equipped
With Printed Wiring Board Assembly
(ED-3C535-30)
M3 INDICA TI ON
Off
-400 volt supply voltage
-200 volt supply vo ltage
Battery voltage
as a 50-microampe re meter. Capacitors C9 and
Cll act as smoothing capacitors in these two
measurements . The cathode currents of the two
klystrons, V1 and V2, are indicated by the voltage
drop across cathode resistors R2 and R18. The
two klystron cathodes are bypassed to ac ground
by capacitors C1 and C6. Resistors R35 and R36
are used to calibrate M3 when it is used to measure
transmitter power output via DET 1, the 53A
power monitor detector. This provides a means
for monitoring power output changes over periods
of time. AGC voltage is measured directly with
M3 converted to a 6-volt full-scale meter with
multiplier resistor R34.
B.
Meter Circuit (M 1)
This meter, used in conjunction with other
controls, provides a means for monitoring
and adjusting transmitter frequency and deviation
and receiver AFC error voltage (panel marked IF).
Figure 17 is a diagram of the M1 circuit. Transmitter
frequency is measured by passing the RF output
through bandpass f il ter FL2 and DET 2 which
produces a de voltage that is applied to Ml. The
selectivity of FL2 causes a peak indication on M1
when the assigned frequency is reached. Transmitter
deviation is measured by observing the drop in
the M1 power output indication relative to the
unmodulated power output when a modulated signal
is fed through FL2. To measure this output
2.07
Page 19
SECTION 409-300-102
/
-20V
,------
-
--1
I
/
R3l
R32
10
-4'00V
/
/
56
1'
R37
M3
1---....JV\~----cr/
12
-20
-400
-200
-24
10
II
12
R28
-600V
-1
400V
MEASURES
SW POS
I
=
~
II
o:-:--- -
II
R33
o':f
VOLTS
VOLTS
VOLTS
VOLTS
R29
-24V
-400V
Fig. 16-M3 Metering Circuit-Simplified Schematic Diagram
reduction accurately, AT2 is used to provide a
calibrated reference level change independent of
detector accuracy. Deviation is adjusted by inserting
a fixed level tone into the transmitter baseband
amplifier and adjusting the amplifier gain control
for a specified reduction of the M1 indication.
Sensitivity of the adjustment is improved by an
expanded scale feature provided by a bucking
voltage obtained from the -20 volt supply. The
bucking voltage is secured via R15, R16, and R17,
with R16 giving control of the voltage. Increased
sensitivity is obtained by decreasing R13 (SENS)
which controls the current in Ml. R14 is the
detector load resistor.
The IF is monitored withS1 in the IF position,
placing the meter across the AFC amplifier
in the IF unit which is driven by the discriminator
output. · Meter M1 is a zero-center type; therefore,
any departure from zero indicates a shift in the
IF from its nominal value of 70 MHz.
2.08
C.
Klystron Repeller Voltage Control Circuit
Klystron repeller voltages are adjusted with
potentiometers R19 and R25, designated
XMTR RPLR and BO RPLR, respectively, as
illustrated in Fig. 18. For klystron protection,
internal stops are provided at about 12,000 ohms
which prevent the repeller voltages from being
reduced to the same potential as the cathode. The
swinger arms of the potentiometers are bypassed
with capacitors C7 and C8 to redu~e noise modulation
of the klystrons. The cathodes ~re also placed on
ac ground by capacitors Cl and C6. Diode CR1
and resistor R1 are placed between the BO repeller
and cathode to prevent the repeller from becoming
highly positive with respect to the cathode, which
would destroy the klystron. With this arrangement,
the highest positive potential that the repeller may
assume is limited to the maximum forward drop
across CRl, or about 0.6 volt. An identical circuit
is provided for the transmitter klystron although
the components, CRll and R41, are not located on
the meter and control panel.
A simple transmitter linearity circuit is
included here that sets the repeller voltage
for best average transmitter linearity, thereby
eliminating involved adjusting procedures with
complex test equipment. The circuit shifts the
repeller voltage 2 volts after it has been adjusted
for peak power output. When adjusting for peak
power output with R19, S5 is placed in the TST
position shorting out R22. After completing this
adjustment, 85 is switched to NORM, shorting out
R21 and removing the short from R22. This
produces the desired 2-volt shift and also causes a
small frequency change. It is then necessary to
mechanically retune the klystron cavity for correct
frequency.
2.10
2.09
Page 20
(
D.
Receiver Automatic Frequency Control Circuit
The following AFC circuit description is
limited to that portion of the circuit that
appears on the meter and control panel. A
description of the complete receiver AFC system
is contained in Section 409-300-104. The receiver
AFC voltage corrects for frequency drifts and
appears across R5, as illustrated in Fig. 19, where
. it is added onto the BO repeller supply voltage.
The R5 voltage will change with frequency error
in a direction such that a 70-MHz intermediate
2.11
(
ISS 4, SECTION 409-300- 102
,--- --- ,
I
I
I
~~
l
I
I
I
~·
I
l
I
I
I
I
I
(
RF
AT2
(
BANDPASS
FILTER
I
I
Ir--1-,:
(
I
~
~
II
I
lI
-=
II IL_ _ _ _ _
DET£CTDR
r
I
~
e~:iE
SENS
\
FREO
Sl
\
Ml
BIAS
\
Rl6
Rl7
T l-----T--; .0.:...-+-"JJ.f'v-- -'\Nv--o
-20 VOLTS
IF
Rl4
_j
\
\
XMTR
I
fr~g~~l~~
\
Rl
I
___ ___ ,
Rl2
Rl5
I
IL
~RANSMIT~-
_j
TO AFC
AMPLIFIER
Fig. 17-M 1 Metering Circuit-S implified Schematic Diagram
,---- ,
R3
I
I
I
I
I
RCV R
AFC
VOLTAGE
RS
CRI ~lr
I
I
I
11
I
~r-C2
(
BO
I
R25
\.
)
I
RCVRI
MOD I
L _ __ _j
RPLR
400V
I
I
I
I
I
I
Rl
600V
.v1
F-!"
-=
R2
-600V
r------,
I
I
R~2
I
I
I
I
I
I
f1 V2
~· CRII
I
I
I
R22
I
>R41
I
I
T ST
XMTR
RPLR
I
I
l
I
I
Rl9
S5
y
I
If'
----\.
LIN
NORM
R21
TRANSMITT E!!__J CS
RIB
=
-400V
-400V
M3CATHODE
CURRENTS
Fig. 18-Kiyst ron Repeller Voltage Circuit-S chematic Diagram
Page 21
SECTION 409-300-102
frequency is maintained. Amplification of the
receiver AFC error signal is applied as an input
to the control winding of the amp,lifier through R9
and Rll. The resistors limit the amplifier gain
and prevent complete shorting of the control winding
when the input is shorted by switch S2. The
amplifier biasing winding draws current from the
-20 volt regulated supply though R26 and R27.
M3 is used to measure the amplifier output voltage
during initial R27 bias-current adjustment. The
AFC correcting voltage is obtained from a~ 1800-Hz
square wave derived from the power supply. The
square wave is fed through two windings having
a reactance that is controlled by the input de error
signal. The square wave is rectified and, because
of the variable reactance effect, appears at point
4 as an amplified version of the de error signal.
Because the AFC voltage at 4 is not clean direct
current, it is filered by C5, R8, and C4 which form
a pictype filter. To keep the BO within its correct
mode, the full AFC voltage is not applied to the
repeller and, therefore, the voltage is divided by
R5 and R7. Capacitor C3 is across R7 to improve
the phase margin of the AFC loop and thereby
protect the circuit from loop oscillations.
An AFC squelch circuit is provided for
disabling the AFC circuit during deep fades
to prevent AFC lockout. During deep fade conditions,
relay Kl releases its short· across RIO, reducing
the magnetic amplifier gain, thus preventing the
AFC loop from shifting the BO off frequency. The
control for relay Kl is initiated in the IF amplifier.
2.12
~odification
E.
The addition of a printed-wiring board
assembly (ED-3C535-30) modifies the TL-1
meter and control panel (Fig. 15) as follows.
(a) Additional filtering in the BO cathode circuit.
(b) A network to prevent oscillations in the
AFC loop due to the new IF-to-baseband
receiver arrangement.
(c) A reference voltage supply circuit which
provides a reference voltage for the AGC
metering circuit. This circuit is accessable from
the front of the panel by means of a new AGC
CAL control.
When the J99296G-2 receiver IF and baseband
unit is used in the system. The addition
Page 22
3.
(
(
BAY ARRANGEMENTS AND INTERCONNECTIONS
For reference purposes, the TR bays in a
radio system are given a particular designation
that is determined by their location in the system.
This nomenclature is illustrated in Fig. 25 which
shows the uses of the bays in the system and the
paths taken by the multiplex, order-wire, and alarm
signals.
3.01
3.02
(
The types of radio stations which make up
a TL-1 route are as follows.
(a) Terminal Station: This is a terminal
(Fig. 20) of the radio system which connects
to wire facilities or message terminal equipment.
(1) Near Terminal (NT}: The radio terminal
which is nearest the attended control point.
(2) Far Terminal (FT): The radio terminal
station farthest from the above attended
control point.
to the Meter and Control Panel
2.13
2.14
of an external squelch relay is required to provide
for squelching the baseband output when an excessive
fade occurs. This relay is mounted on the adapter
bracket that supports the receiver unit. This
adapter bracket also contains the terminals that
are required for electrical interface between the
radio RF panel and the receiver IF and baseband '
unit.•.
(b) Repeater Station: An intermediate station
where the signal is received, amplified, and
transmitted. This station may be equipped to
drop and add groups of message channel circuits.
A repeater consists essentially of two terminals
operating back to back. For purposes of
identification, these equipments are identified as
follows:
(1) Near Repeater (NR): The transmitterreceiver equipment which transmits toward
the near terminal and receives from the near
terminal
(2) Far Repeater (FR): The repeater station
equipment which transmits toward the
far terminal and receives from the direction
of the far terminal
(
\
ISS 4, SECTION 409-300-102
(
C3
(
C5
C4
TO 80
REPELLER
r --------------,
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POWER SUPPLY :
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R26
R27
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TO M3
AFC
BIAS
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MAGNETIC AMPLF
r-D-Kl
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TO IF AMPLF
-20V
Fig. 19-Receiver Automatic Frequency Control Circuit-Schema tic Diagram
(3) Spur: The radio equipment at a repeater
station which accommodates transmission
to a radio spur or branch route.
(
Waveguide interconnectio ns between the
antenna and TR bays vary and depend upon
whether the system is diversity or nondiv:ersity,
whether the location is an indoor or outdoor
installation, and the number of channels in a system.
For example, when only one polarization is utilized
in an antenna, as with a 2-channel nondiversity
system, a transducer is used in place of the
polarizer. Also, the isolator between transmitters
and receivers is installed only after a system reaches
a certain size. Waveguide interconnections and bay
arrangements for all of the different cases are
illustrated schematically in Fig. 26 and 27.
3.03
Two baseband interconnectio ns are needed
from the transmitter and receiver to the
diversity switch panel or order-wire and alarm
panel. These connections are made directly from
the input and output jacks of the trasmitter and
receiver to a terminal strip on either of the other
two panels. In diversity systems, an AGC voltage
connection is made between the receivers and the
diversity switch panel. This connection is made
via TSA, a 48-terminal connector in the TR bay.
3.04
)
~-
-
1»-----t--- -,
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1.--------'---,
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'----r----'
1-------.
1m TRANSMITTER
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TO RECEIVER
L __
MXI
MX2
@CHANNEL DROPPING/COMBINING NETWORK
Fig. 20-Typical Terminal-Type Transmitter-Re ceiver
Bay Arrangement- Block Diagram
Page 23
SECTION ··419-300-102
The baseband signal and AGC voltage paths are
shown for a typical diversity system at a repeater
station as illustrated in Fig. 21.
Transmitters and receivers are connected to
the antenna waveguide runs by means of
channel dropping and combining networks (Fig.
23). The networks extract or insert one channel
while allowing others to pass through without
interference. The combining networks, utilized by
the transmitter, are located nearest the antenna
wliile the dropping networks appear in the latter
half of the waveguide run. The last receiver in a
run does not require a network because the only
signal in the guide at this point is the one intended
for this receiver. That is, other received signals
are droppped before this point, and the transmitted
signals do not travel backward, but travel only
toward the antenna.
will appear in D. A signal in the input ARM
incident on the junction will, therefore, be divided
into the side arms and trayel on to the two
band-reflection filters. These filters are designed
to reflect frequencies lying within a specific channel
band and pass all other frequencies. Frequencies
outside of the reflection band of the two filters
will pass through the filters to ARMS A and B of
the output hybrid. Here they will have equal phase
and amplitude, their vector difference will be zero,
and none of the power will enter D. The two
signals will combine and pass through C to the
succeeding receivers. The signal lying within the
band of the reflection filters will be reflected back
to ARMS A and B of the input hybrid. The two
signals arrive at these connections in opposite phase
since one of them has traveled twice over an extra
quarter wavelength of line. Their vector sum will
be zero, and no power appears in terminal C of
the input hybrid. All of the power appears at
terminal D as the dropped channel.
A network is composed of two hybrid
junctions, two identical band-reflection filters,
and a waveguide terminating section. Figure 22
is a block diagram that illustrates the action of a
channel dropping network. Each of the hybrids is
analogous to a low-frequency hybrid coil and
operates as follows. An input signal in line C,
incident on the hybrid, is divided equally and with
equal phase into side ARMS A and B, but does not
appear in D or reappear in C. Also, signals in
A and B are incident on the hybrid; a wave
proportional to their vector sum will appear in C
and a wave proportional to their vector difference
Conversely, this circuit inserts signals lying
within the band of the reflection filters in
the main line without interfering with any of the
signals pas!;ling though it at other frequencies. For
combining purposes, a transmitter output signal
would enter the upper hybrid, as illustrated in Fig.
22, through ARM D. It would then split into the
side ARMS A and B with a 180-degree phase shift
and travel down the arms to the filters. Here
the signals are reflected and arrive at ARM C in
phase and, therefore, add and pass into the main
waveguide to the antenna.
4.
CHANNiL DROPPING AND COMBINING NETWORKS
4.01
(
(
4.02
r-- ------.,
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AGC
r-------,
r---------,
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r-~~~~----~
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BB
I
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DIVERSITY
SWITCH
I
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IL ________
TR BAY
.JI
ORDER
WIRE
88
I
I
I
AND
ALARM
I
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IL ________
TR BAY
_jI
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.,
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TR BAY
I
L--------~
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TR BAY
I
L--------...J
Fig. 21-Automatic Gain Control and Baseband Signal Paths-Block Diagram
Page 24
I
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,-------..,
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1
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4.03
(
ISS 4, SECTION 409-300-102
c·
INPUT
SECTION
HYBRID
TITLE
JUNCTION
SD-97035-01
Tlr1 Radio-Applica tion Schematic
SD-81507-01
Tlr1 Radio-Power Supply Circuit
SD-97038-01
Tlr 1 Radio-Transmitter-Receiver
Circuit
SD-97039-01
TL-1 Radio-Rece iver IF and
Baseband Circuits
SD-97045-01
Station Grounding-A C Power
and Lightning Protection Circuit
SD-97042-01
Tlr1 Radio-Divers ity Switching
Circuit
SD-97056-01
ON Carrier Telephone-Application
Schematic for Combining Circuits
for Use with Tlr1 Radio
SD-:.95296-01
Tir 1 Carrier-Application Schematic
for Radio Applications
SD-95296-01
Tir 1 Carrier-Application Schematic
for Radio Applications
SD-97100-01
Tlr1 Radio Alarm Encoder Circuit
SD-97041-01
Tlr1 Radio Order-Wire and Alarm
Circuit
SD-81557-01
Power Service and Distribution
Circuit for Tlr1 Radio Stations
SD-81559-01
Air Navigation Obstruction lighting
Circuit for Tlr 1 Radio
A
L----.,....-+- ..;.._- DROPPED
CHANNEL
(
..
(
A
HYBRJO
JUNCTION
OTHER CHANNELS
•
Fig. 22-Channel Dropping Netwerk-Bioc k Diagram
Figure 23 is an illustration of the 1402-type
channel dropping and combining network.
The hybrid junctions, located at both ends, are
composed of an E ARM (C), two side arms (A
and B), and H ARM (D) which is conjugate to the
E ARM. The E ARM waveguide is split by a
wedge to form the two side arms. The H ARM
is coupled to the side arms by means of two coaxial
waveguide probes that are themselves coaxially
connected. Tuning studs are located within the
hybrid to minimize reflections caused by discontinuities
in the wedge, probe, etc. The channel-reflec tion
filters are located between the side arms of the
two hybrid junctions. Different filters are used
for different channels. There are 24 different
codes of reflection filters required for the 24 radio
channels.
4.04
5.
(
5.01
REFERENCE LIST
The following drawings are related to this
section:
SECTION
SD-3C250-01
TITLE
Tir 1 Radio Changes for 600-Circuit
Loading
Page 25
SECTION 409-300-1 02
Fig. 23-1402-Type Channel Dropping and Combining Network
Page 26
ISS 4, SECTION 409-300-102
PART OF
P7A AND P78
80 RPLR
NOTES:
I. M2 TIMER HAS BEEN MANUFACTURE
DISCONTINUED (MD) .
2. REFER TO LATEST ISSUE OF
SD- 97038-01 FOR COMPONENT
VALUES AND CODES.
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Fig . 24-Typical Meter and Control Panel
Circuit--Schematic Diagram
Page 27
ISS 4, SECTION 409-300-102
""AR-END TERMINAL STATIOI'I
TYPICAl Tl-1 RADIO SYSTEM
DJA(fRAM SHOWIN(i ORDER-WIRE
A/10 Mill TIPL EX FUN( TION!!.
~AI.-,
NCAR-E:NO TERMINAL STATION
INf"CRMCOMT£' STATION
JUNC T/ON iNTF:I<MCDIAT£ STA TfON
[;:;~~!<J SPUR
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LEG£ND
INTEJ<M£0/AT£ Ole
NEAR-END
JVNCriON INTERMEDIATE
TERMINAL
STATION
C'OMPOSt7C BASEBAND SiliHAL
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T/17 BAY
TIRBAY i
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Fig. 25-Typical TL-1 Radio System-Functional Block
Diagram
Page 28
ISS 4, SECTION 409-300-102
LEGEND
I.
~
2.
3
NEAR-END
TERMINAL
STATION I
AIR PATH
-z NO.2 s-
INTERMEDIATE
STATION
STATION 2
IS A CHANNE·L DROPPING/COMBINING NETWORK.
1----=ii
5.
TRANSMITTERS PAIRED FOR PROTECTION ARE COMBINED
AT A SPLIT PAD.
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A BASIC LETTER AND ITS PRIME LETTER CONSTITUTE AN
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BE CONNECTED TO A 2-WIRE LINE CIR<OUIT THROUGH
THE USE OF A HYBRID.
RECEIVERS PAIRED FOR PROTECTION ARE COMBINED AT A
DIVERSITY SWITCH.
INTERMEDIATE
STATION
STATION 4
v
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IS AN ISOLATOR.
4.
AIR PATH
NO.3
INTERMEDIATE
STATION
STATION 3
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6. H- HORIZONTAL SIGNAL POLARIZATION
7.
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8. T- TRANSMITTER RADIO EQUIPMENT
9. R- RECEIVER RADIO EQUIPMENT
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--
-c=~
) C = J - - - - (HIIi,orst9Al ----c::::JZ
/(=]- -
-
(V)I0,995(3A) -
-
-IH)I0,715(4A) - -
=:Y,T
·
1
T
-~
- - (H)I0,995(2A)
-
-(V)I0,875(6A)
(HJIIJ55(5A)
T
(V)II,075(9A)
T
(H)I0,995(3A)
T
- - (HJI0,795( 10 A ) - i T C : : J - - - IHII0,7551!Al - - - -c::Jr.;R
T
T
T
R
y'
z'
x : = J - - -(H)I0,915(7Al ---[=~
~:::J-- -(V)I0,795(IOA)-- -c=r.:
~RC::J--
-
- - (VJII,035(12A) - -
-{=~
(H)I1,285(12B)--
R
z
--
R
- - - !V)I0,715(4A)
--
- - (V)I0,915(7A)
x'
T
--
T
- - (V)I0,755(1A) - -
(HJIO,B35!11Al - -
Fig. 26-Transmitter .. Receiver Arrangement and
Frequency Plan-Block Diagram
Page 29
ISS 4, SECTION 409-300-102
IF CAB INETS ARE
USED IN SYSTEM
I DIV CHAN
OR
. [ 2 .NONDIV CHAN
I DIV CHAN
OR
2 NON DIV CHAN
IF NO CABINETS ARE[ l, 2 , OR 3 DIV CHAN
OR
USED IN SYSTEM
MORE THAN 3 NONDIV CHAN .
.
USED FOR I NONDIV CHAN
IF CABINETS ARE USED
IN SYSTEM
OR
I ,2, OR 3 NONDIV CHAN
IF NO CABINETS ARE
USED IN SYSTEM
a:
~
TRANSDUCER
N
a:
c:r
1ST
DIV
2ND
DIV
3RD
DIV
I, 2 ,OR 3 DIV CHAN
OR
MORE THAN 3 NONDIV CHAN
3RD
DIV
~---+~<,....-< · -.. ~>---+~<~-<·-·..)-+to.....-..,
J
J
IF CABINETS ARE
USED IN SYSTEM
%
IF NO CABINETS ARE
USED IN SYSTEM
2ND
DIV
---+wo"""""-c•-• .;>-~)l't--<
1ST
DIV
• - • .;>--hell+--~
a:
laJ
N
...J
a:
c:r
...J
0
0
a..
TRANSDUCER
a..
USED FOR I NONDIV CHAN
IF CABINETS ARE USED
IN SYSTEM
OR
1,2,0R 3 NONDIV CHAN
IF NO CABINETS ARE
USED IN SYSTEM
..
1ST
REG
t
2ND
REG
3RD
REG
3RD
REG
2ND
REG
FAR-END TERMINAL _ _ _ _ _,_,;__ ____.....14•. - - - - - - - - NEAR-END TERMINAL
INTERMEDIATE STATION
1ST
REG
j
LEGEND
I:
IS A CHANNEL DR 0 P PING/COMB IN I N G NETWORK
2. I =--+I IS AN ISOLATOR
®
3. RECEIVERS PAIRED FOR PROTECTION ARE COMBINED AT
A DIVERSITY SWITCH
4. TRANSMITTERS PAIRED FOR PROTECTION ARE COMBINED
AT A SPLIT PAD
5. T- TRANSMITTER RAD I 0 EQUIPMENT
6. R- RECEIVER RADIO EQUIPMENT
GROWTH PATTERN
FOR T/R BAYS I TO 6: TWO-WAY NONDIV CHANS AND
I TO 3 TWO -WAY D IV CHANS
Fig. 27-TransmiHer-Receiver Growth Pattern-Block
Diagram
Page 30
30 Pages