Hal Communications ST-6000 User manual

STI6OOO
FSK
DEMODULATOR
INSTRUCTION
MANUAL
HAL COMMUNICATIONS CORP.
BOX 365
URBANA, ILLINOIS 61801
QUALITY CO M M U NICANONS EQ U I PM ENT

STI6000
FSK
DEMODULATOR

HAL 5T-6000 FSK DE|VIODULATOR / KEYER
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Copyright @ 1976 by HAL Communications Corp., Urbana, I I I inois.
Printed in the United States of America. All rights reserved.
Contents of this publ ication rnay not be reproduced in any form
wi thout the wr i tten permi ss ion of the copyr i ght owner.
February, 1982 Printing

2. SPEC IF ICAT IONS
CONTENTS
}. INTRODUCTION
3. I NSTALLATI ON
3.1 lnitial
3.2 Use of
3 .2.1
3.2.2
) .2.3
) .2.\
3 .2.5
3.3
4.4
4.5
l+.6
t+.7
I{.8
[.9
4. l0
4.lt
\.12
I{. 13
HAL ST.5OOO DEMODULATOR
lnspection . . . . : . . . . o , . . . . .
Factory Supplied Cables . . . . . . o . .
Audio lnput Connection. . . . . . . . . . .
l-l
2-l
3-l
3-l
3-2
3-2
3-2
3-2
3-4
3-4
3-7
3-7
3-7
3-7
3-B
3-8
3-9
3-9
3-9
3-l I
3-l I
3- 13
Audio 0utput Connection
t-oop I Cable Connection
Motor Power Connection.
KOS Cable Connection.
Separate Keyboard Connection. . . . . . . .
RS-232CCableConnection...... . o
CW lD Key Cable Connection.
AC Power Cord Connection.
Ground Connection r . . . . . . . . . . . .
Connection to the ST-6000.
Use of External Loop Suppl ies and
Mul tiple Loop Ci rcui ts.
Separate Printer and Keyboard Connections
Full Duplex 0peration of the 5T-6000. .
External Data Prpcessing Equipment. . .
External 0scilloscope Connections . . . .
Tone Keyer Control Connections. . . . . .
a.a.a.ara.
a.a.a.a.a.
q. I{.1 Front Panel Control s and lndicators.
3.2.6
3 .2.7
3 .2.8
3 .2.9
3.2-lo
Al ternate
3.3.1
3 .3.2
3 .3.3
3.3.\
3 .3.5
3.3.6
4.3, I
\.j.2
\.3.3
Use of the DTH C i rc
Use of t he L im i ter.
Use of the SENSE Sw
Use of the PRINT Sw
The KOS Circuitry.
Use of the Autostar
Ant i space Ci rcu i t.
Switch
i tch.
i tch.
FM vs Al4
I.a.a.a-.a.a.a.a.a
tCircuitry.......o..
\.2 Simplified Operating Procedure. . . . . . o . . . .
4.3 Reception of Radio Teleprinter Signals. . . . . . .
Receiver for FSK Reception. . i G . . . . .
Receiver for AFSK Reception . . . . . . . .
Tuning a RTTY. Signal. . . . . . . . . . . .
4-l
\-2
\-3
\-3
4-5
4-5
4-7
4-8
4-8
4-9
4-9
4- r0
4-t r
Use of the ATC Circuit . . . . .-. . o . . . . . . .
| - . . . \-7
Tone Keyer Clrcuit . . . . . . . . . . . . . . . r 4-ll
Transmitting Radio Teleprinter Signals . . r . . . . 4-12
4.13.1 Transmitting FSK Signals. . . . . . . o . ; 4-lZ
\.13.2 Transmitting AFSK Signals . . . r . , . . 4-ll{
4.13.3 Adjustment of the 5T-6000 Tone Keyero . . . 4-14
tt

5. ST-5OOO CIRCUIT DESCRIPTION . . . . . . . . . . . .
5.1 ST-5000 Arralog Processing Circuits lnput Circuit
Board. . . . . . . . . . . . . . . . .
5.1.1 lnput AGC Circuit . . . . . . . . o . . . .
5.1.2 lnput Bandpass Filters. . . . . . . . . . .
5.1.3 Limiter Amplifier . . . . . . . . . . . . .
5.1.4 Discriminator Filters. o.... ....
5.1.5 Discriminator Detectors . . r . . . . . . .
5.1.6 A/S Amplifier and Detectors . . . . . . . .
5.1.7 Active Lowpass Filter . . . . . . . . . .
5.1.8 ATC Circuit . . o . . . . . . . . . . o
5.1.9 Tone Keyer. . . . . . . . . . . . . . . . .
5T-6000 Control Circuit Board. . . . . . . . . . . .
5.2.1 Slicer and DTH Circuits . . . . . . . . . .
5.2.2 Ant ispace C i rcu i t
5.2.3 Pre-autostart Data
5.2.\ Autostart Circuit . . . . . . . . . . . . .
5.2.5 Standby Circuit . . . . . . . . . . . . . .
5.2.6 Post-autostart Data 0utput. . . . . . .
5.2.7 Loop Keyer Stages o . . . . . . . . . . . .
5.2.8 RS-23z/MlL-l88 tnterfaces . . . . . . . .
5.2.9 KOS Circuit . . . . . o . . . . . . . . . .
5.3 Front Panel lndicators . . . . . . . . . . . . . .
5.\ Power Supply . . . . . . . . . . . . . . o . . . . .
5.5 Oscilloscope . . . .
5.6 CabinetWiring . . . . . . . . . . . . . . . . .
5.7 User Servicing
5.8 TroubleshootingGuide.. ... ....
APPENDIX A: RF-lnduced Problems . .
WARRANTY
5-l
5-l
5-l
5-r
5-r
5-2
5-z
5-z
5-2
5-3
5-3
5-\
5-t1
5-l{
5-\
5-5
5-5
5-6
5-6
5-7
5-7
5-8
5-B
5-9
5-9
5-10
5-l1
6-t
7-1
5.2
0utput.........
tll

HAL ST-5OOO DEMODULATOR
ST-5000 Front Panel Controls . c . . 4-l
ST-5000 Front Panel lndicators . . . . . . \-2
Figure IST-5000 Demodulato. (photo)
TAA LE S
Table 4.1
Table \.2
I LLUSTRAT I ONS
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.\
Figure 3.5
F i gure 3.6
Figure 3.7
F i gure 5.1
Figure 5.2
Figure 5.3
Figure 5.\
Figure 5.5
Figure 5.6
Figure 5.7
Figure 5.8
Figure 5.9
Figure 5.10
Figure 5. I I
Fi gure 5.lZ
Fiqure 5. I3
Figure 5.1\
Figure 5.15
Figure 5.15
Figure 5.17
Figure 5. lB
ilstandard" Cabl e Connect ions to the ST-5000
Loop Connections to the ST-5000 . . . . . . . . . . . o
RS-232 l/0 Connections to the ST-5000. . . . . . o . . .
Preparation of the 5T-6000 Connectors . . . . .
Alternate Loop Connections . . . . . . . . . . . . . .
Connections for Full-Duplex Operation ! . . . . . . . . .
Connect ions to Externa I Data Process i ng Dev i ces . . . .
5T-6000 BlockDiagram . . . . . . . . . . . o . .
ST-5000SchematicDiagramConventions.......
lnput AGC Circuit . . . . . . . . . . . . o . . .
lnput Bandpass Filter . . . . . .
Limiter Amplifier . . . . o . .
Discriminator Filters . . .
Discriminator, Meter Amp., Lowpass Filter, Atc . . .
ToneKeyer................o
Slicer, Antispace, Autostart . . . . o . o .
LoopDrivers, LoopSense ... o.. ..
RS-23?/lllL-lBB lnterface . . . . . . . . . . . .
KOS Circuit . . . . . . . .
PowerSupply..........
0sci I Ioscope.
lnput Circuit Board Layout . . . . . . . . o . o . .
Control Circuit Board Layout . . . .-. . . . . . .
Oscilloscope Circuit Board Layouts . o . . . . . .
Ci rcuit Board lnterconnections
IV
3-3
3-5
3-6
3-9
3- I I
3- 13
3-15
5- 14
5-i5
5- 15
5-17
5-18
5- 19
5-20
5-21
5-22
5-23
5- 2\
5-25
5-25
5- 27
5-28
5-29
5-30
5-31

I, InrnoDUCTroN
The Hal Communications Model ST-5000 is a high performance FSK
demodu Iator and tone keyer des igned for use with rad io tel epr inter systerrs.
The ST-5000 incorporates the features and performance characteristics of
previous HAL demodulators as wel I as offering some features previously
not avai lable.
The ST-5000 is an audio tone type of demodulator and keyer. Audio
tones from the receiver, representing the "markrr and ilspace" teleprinter
code states, are converted into keying pulses by the demodulator section.
Active input and discrinrinator filters are used in the ST-5000 so that a
wide range of input f requenc ies can be accomodated . Turo standard aud io
tone sets are normal Iy stocked by the factory and special tone sets within
the 1200 3000 Hz frequency range are available on special order. The
standard tone sets are based on a mark frequency of 1275 Hz ("low-tone"
set) or a mark frequency of 2125 Hz ("high-tone" set) for frequency shifts
of l7O H2,425 Hz, and B5O Hz. The tone keyer section of the ST-5000
generates the same set of tones for transmitting in addition to a narrow-
shift tone for Morse code identification.
The demodulator uses a pre-filter agc system, oR active bandpass
filter, a high gain, wide bandwidth limiter, and active detector circuits.
This combination gives outstanding performance for a wide range of input
signal apl itudes even in the face of strong interfering signals. The
Iimiter stage gain can be reduced for non-limiting operation ("AM"). The
pre-f ilter agc and active detectors also assure improved non-limiting per-
formance when compared to previous demodulators. A three pole active lot',,pass
f ilter follows the detector stages to reduce the post-detection noise bandwidth.
An Automatic Threshold Correction (nfC) circuit can be switched into
the signal chain to provide correction for bias distortion generated by
the propagation path. This feature can also be defeated with a front
panel switch if desired. A Decision Threshold Hysteresis (0fH) circuit
can also be switch selected to provide correction for multi-path propagation
d i stort ion of the tel epr i nter s i gna I
CM0S digital circuitry is used to provide the Jutomatic printer and
motor control as wel I as the ant i space feature. The 5T-6000 autostart
circuit senses the presence (or absence) of a val id teleprinter signal.
lf the input signal is not recognized as a teleprinter signal, the printer
is held in the rrmark-hold'r cond it ion. I f more than twenty seconds pass
without recognition of a valid signal, the pc\{er to the printer motor is
removed. The response t ime of the autostart c i rcu it is srvi tch selectabl e
to allow "FASTT' (1.5 sec.) or "SL0W" (3.5 sec.) response. An antispace
circuit is also included in the digital control section that I imits the
duration of a space signal to 250 ms or Iess, preventing the "running-
open" mach i ne cond i t ion on cont i nuous space tones.
As mentioned earl ier, the tone keyer section generates the same tone
set as is used in the demodulator section to assure true "transceive"
conditions. The tone keyer will also generate an additional narro\^r-shift
tone that can be connected to an externa I keyer c i rcu it for Mc,,rse code
I-t

identif icatiorr. AII tones of the tone keyer are derived from high fre-
quency crystal controlled oscillators. The output signal is a low dis-
tortion sinewave generated in a digital-to-analog converter and then
f iltered in an active low-pass f ilter. A wide range of output ampl itude
(into 500 ohnrs) it available f rorl the ST-5000, adjustable with an internal
control. Unlike previous demodulators, the tone keyer data input circuit
is not internal Iy connected to the demodulator but is available on a rear
panel connector. Thus, separate transmit and receive circuits (full-duplex)
can be accomodated by the Sf-6000. Conversel y, wi th appropr i ate rear-panel
jumpers, the tone keyer can be connected to the demodulator for a common
transmit receive circu it (lralf -duplex) ut was the case for the ST-5
demodulator. However, the shift of the tone keyer is controlled by the
f ront panel SH IFT switches. Al so, the SEIISE switch (tlOnm REV) controls
both the tone keyer as well as the demodulator.
The 5T-6000 input and output circuits have been designed to allow a
maximum of user flexibility. Many signal and control lines have been
brought-out to rear panel connections. Both pre- and post-autostart data
signals are available on the rear panel as are the inputs and outputs of
two separate high-level loop switches. fhe internal 175 volt, 50 ma Ioop
supply is also connected to the rear panel. Thus, the demodulator output
can be used to directly key the loop or be first passed through additional
signal processing (such as the popular UART and digital control devices),
and then routed back through the ST-5000 keyer stages, with the option of
using or not using the internal loop supply of the 5T-6000. tn addition,
the ST-6000 has both output and input signal connections that are compatible
with both the ilA - RS-232C and MIL-STD-IBBC data signal Ievels.
The ST-6000 also includes a Keyboard Operated Switch (fOS) circuit
that can be used to automatically switch the transmit receive cont;-ol
circuitry of the station. fhe f..0S circuit senses teleprinter keyboard
and CW identification signal status. lf either the keyboard or the
CW-lD key is used, the K0S switching transistor turns "0|J" (low impedance to
groun,j). The KOS circuit also places the 5T-6000 demodulator circuits in a
"standby'r status to prevent feedback from the receiver whi le transmitting.
The NPN K0: switching transistor can be used to control a DC relay that is
supplied f rom a positive voltage source or a push-to-talk (PTT) control I ine
in a transn'ritter (providing the PTT Iine is derived from a positive DC source.)
Since the K0S sensing I ine is connected to the rear pan6l, it can also be
t r i ggered by externa I dev i ces .
The aud io input to the dt,modu lator and the aud io output f rom the
tone keyer are both 500 ohms balanced (o. unbalanced if jumpered) with
respect to gr,:u:,d and use aud io transformers to maintain DC isolation.
The oscilloscope signals for a crossed-ellipse oscilloscope display are
connected to a rear panel connection. The ST-5000 is furnished with
a front pane I tun i ng osc i I I oscope.
lnternal , e lectronical ly regulated + 12 volt power suppl ies provide
operating voltages for the demodulator, control, and tone keyer sections
of the 5T-6000. A 175 volt, 50 ma. loop power supply is also included
as a part of that option. fhe main power transformer of the ST-5000 can
l-2

be connected for operation with either 105 to 125 VAC or 210 to 25a VAC,
50 or 50 Hz power sources. Both the power line and the loop power supply
are fused with fuses accessable from the rear panel of the unit. The
5T-6000 requires approximately 20 watts of AC power and is housed in
an attractive brown and tan cabinet that matches the DS3100 ASR and
other HAL Communications Video Display Terminals. The cabinet can
be supplied for either table or relay-rack mounting.
A complete set of cables and connectors are furnished with the
5T-6000 ro simplify rhe initial instal Iation of the Sf-5000. lf you
are anxious to try your ST-5000, it is suggested that you skip to sections
3.1 and 3.2 of the instal lat ion chapte.r and then read sect ions 4.1 and
\.2 of the operation chapter before turning the equipment on. The balance
of this manual should then be studied before attempting any "custom"
connect ions.
la
!-_1

2, SpTctFICATIoNS
Demodulator Section:
lnput data: Ser ia I Data
Data rate: Up to ll0 baud
lnput lrrrpedance: 500 ohnrs, balanced and isolated f rom ground
I npu t frequenc i es:
"Low-tonerr set: Mark = 1275 Hz
Space = 1445 Hz (tZO Hz shift)
1700 Hz (\25 Hz shift)
2125 Hz (BSo Hz shift)
"H igh-tone'r set: Mark = 2125 Hz
2295 Hz (tZo Hz shift)
2550 Hz (\25 Hz shift)
2975 Hz (BSo Hz shift)
"Special" tone sets Audio frequencies between 1200 and 3000 Hz;
mark tone must be common to all shifts'
850 Hz- max imum recornmended sh if t.
lnput s ignal ampl itude: Full I imit ing (fm mode) for s ignal
Ievel s betvreen -50 dBm and +20 dBm
("pproximately I mV to 'l 0 V rms).
When lrAMrr mode (non-l imit ing) is used,
input signal should be in the range
-40 to +20 dBm (approx imarely l0 mV
to l0 V).
lnput Fi lter -3 dB Bandwidth: 850 Hz shift - lZ5O Hz
(all tonesets) \ZSHz shift- l75Hz
l7O Hz shift - 275 Hz
Discriminator filters -3 dB
Bandwidth (all rone sets): 850 Hz shift - lB0 Hz_
\25 Hz shi ft - 125 Hz
l7O Hz shift - 7A Hz
Low-pass f i I ter bandwidth: 82 Hz (min imum for I I0 baud)
Tone Keyer Sect ion:
I nput data:
Data rate:
lnput signals:
Serial Data
Up to ll0 baud
Can be external Iy connected for:
l. sensing of current Ioop
?. sens
3. sens
4. sens
ng of EIA-RS-232C signals
ng of MIL-STD-IBBC signals
ng of "drV'keyboard contacts
5. C'/-lD key
6. CMOS-compatible signal
mark = 0V
space = +12 V
Standard - sanre tones as derncdulator input
Special - any tones in the 1200 to 3000 Hz
frequency range, mark tone common to all
shifts. ln addition, a CW lD tone is
generated 100 Hz below the mark tone;
Ct^/ lD = l 17 5 Hz f or " lov;- tones", 2A25 Hz
for "high-tones".
0utput tones:
2-1