Tune Pwb Assembly A2A6A5 Circuit Descriptions; System Tune Cycle; Ready Latch Function - Harris RF-131 Instruction Manual

CONTROL HEAD
When the system is in sideband mode, the
CW /RATT mode ground is high, causing Zl-10 to
go low and disabling the CW hold input (pin X)
control. The high CW /RA TT mode ground enables
gate Z2-8, allowing the auxiliary keyline to be acti-
vated by a ground from either the + 12V PTT key
input from the front panel microphone connector
A2J 19 (when microphone is switched into a
channel) or the PTT relay A2A6A3K3.
5 TUNE PWB ASSEMBLY
A2A6A5 CIRCUIT DESCRIPTIONS
Tune PWB A2A6A5 monitors frequency
changes, TUNE pushbutton (TUNE portion of
TUNE/READY pushbutton A2A6S5) closures,
local/remote control changes, and other situations
that require the retuning of the system transmitter.
Refer to Figure 13 during the following descrip-
tions.
5 .1 System Tune Cycle
The tune cycle is initiated by the operator, who
gives the tune command by either keying the
system when the Antenna Coupler is at home posi-
tion (systems without an antenna coupler bypass
the tune cycle), or by depressing TUNE/READY
pushbutton A2A6S5. When the Antenna Coupler
is at home position, keying the system will send the
Antenna Coupler through the active and end por-
tion of the tune cycle. When the TUNE/READY
pushbutton is depressed, the TGC Attenuator will
be at maximum attenuation, the Antenna Coupler
will be sent to home position, and the system will
be keyed. These conditions cause the system to go
through a complete and active tune cycle.
The active portion of the tune cycle starts with
the Antenna Coupler sending a
+
20V carrier insert
signal, and the system Power Amplifier sending a
+
28V Interlock signal, to Tune PWB A2A6A5.
These conditions cause unmuting of RF Output
Module A2A 7, lighting of the TUNE lamp in
TUNE/READY pushbutton A2A6S5, and the
grounding of the exciter tune line to Mode Select
PWB A2A6A2 (at A2A6A2P 1-20). Grounding the
exciter tune line causes the appropriate carrier
level, for the system to tune with, to be gated to the
exciter. At the end of the tune cycle, the sytem will
be evaluated to determine if it is ready to transmit.
8
RF-130 SYSTEM
If
the system is ready, the READY lamp of
TUNE/READY pushbutton A2A6S5 will go on.
Tune PWB has two latches that act as memories,
that is, retaining a previously set state. Referring to
Figure 13, these latches are identified as a tune
latch consisting of ZS-6 and Z2-ll, and a ready
latch, consisting' of Zl-11 and Z4-8. ZS-6, Z2-ll,
Z1-11, and Z4-8 are NAND gates.
INPUT A1
- - - - - - - 1
OUTPUT A
A2
82
INPUT 81
- - - - - - - 1
OUTPUT B
When two NAND gate outputs are connected
together, as shown above, a latch or memory cir-
cuit is formed.
A low at INPUT A will cause Gate A's output to
be high. (A low on either A, or
A2
will also cause
OUTPUT A to be high.) This high is routed to in-
put B2. If INPUT B, is not being held low, Gate B
will recognize all high inputs and OUTPUT B will
be low. The low OUTPUT B will hold input
A2
low. If the low at INPUT A, disappears, nothing
happens (that is, no change in state occurs), as in-
put A2 is still being held low. When a low at IN-
PUT B, occurs, the latch will be changed in some
manner. If both INPUT A, AND INPUT B, are
held low, both OUTPUT A and OUTPUT B will
be high. The input that goes high last will set the
latch.
5.2 Ready Latch Function
The ready latch circuit (Figure 13) causes the
READY lamp of TUNE/READY pushbutton
A2A6S5 to go on, and exciter ready information to
be sent to Mode Select PWB A2A6A2, thus enabl-
ing the appropriate channels and setting the correct
carrier level (when the latch is set to ready state and
the system is not tuning, as evidenced by the
absence of the
+
20V carrier insert signal).