Manual / Guide · 1974
ST-6 RTTY Demodulator Instruction Manual HAL Communications Corp Urbana IL 1974
ST-6 RTTY Demodulator Instruction Manual
Manual / Guide · 1974
ST-6 RTTY Demodulator Instruction Manual
5T.6 RTTY DE]UlODULATOR INSTRUCTION MANUAL HAL COMMUNICATIONS CORP. BOX 365 URBANA, ILLINOIS 61801 QUALITY COM M U NICAilONS EQ UIPM ENT sr-6 RTTV DE]UlODULATOR Copyright O 1974 by HAL Communications Corp., Urbana, lllinois. Printed in the U.S.A. All rights reserved. Contents of this publication may not be reproduced in any form without the written permission of the copyright owner. January , 1983 Printing July 25, L975 5T-6 I',IANUAL CHANGES rMPoRrANr: with either the ST-5 kit or Hr::trHI- before making these changes ! The following changes in the 'ST-5 manuaL apply to wired units with sertal number 7 57 and higher and 5T-6 kits shipped afrer July 25 , Lg7 5. These changes are: 1. The 2500 ohm loop pot is no longer avallable. A fixed, 2750 ohm, 20 watt resistor is supplied that replaces both the loop pot (R6i and its series 500 ohm, 5 watt resistor (R5). These changes are reflected in the ne!il pages supplied. , Improved toroid mounting hardware is now furnlshed with all wlred and kit ST-5 demodulators. The proper assembly with these retainers is shown in the nerf, Fi-gure 3A attached. The "Slngle Toroid" detail should be used when attachlng torolds to the 1-170 and the I-850 eircuit boards. The "Stacked Torold" detalL should be used, in the constructl-on of the 2-L70, 2-425, and 2-850 clrcuit boards. Note that the black retainers are threaded and the white retainers are not. The whlte retainers are only used to secure one of the two toroids on the No. 2 circuit boards. The black retalners are used for the other toroid on the No. 2 boards as well as for all toroids on the No. 1 boards. A1so, to mlnimize confuslon, the wirtng of the toroids ls detailed ln the new Flgure 38 attached. The "series Connection" detaiL shoul-d be used in constructlon of all but the 1-170 circuit board. Use the "Parallel Connectlon" detail when constructing the L-170 circuit board. Make the folJ-owing changes in the manual text: Page 16: Delete paragraph 6 and replace it wlth: "Refer to Flgure 3A for the proper technique to use in mounting the torolds to the circult boards. The wirtng Ls shown Ln Flgure 38. " Page L7 Delete the flrst two sentences of paragraph 1 and replace them with: "Refer to Figure 3A ("stacked Torold" detail) for the proper mounting technlque for the two toroids. The wiring is shown ln Figure 38 ("serles connection" z detail) . Additional changes are reflected in the new pages supplied. 3. The rear panel connections for the LooP, KEy, FsK, REMorE, and SCOPE functions have been changed from the phone jacks formerly used to multiple contact connectors. This change has been made to eliminate the possibility of exposed hlgh voltages that could result if a connector is removed from the 5T-6 before an external device is turned off. The change also assures compatibility of the 5T-6 with other HAL RTTY equipment. The use of the multiple contact connector for the loop connection also allows more than one RTTY device to be connected to the 3T-6. The new pages supplied reflect these changes. 4. There are some errors in Figure 13, Circuit Board No. 3 Pictorial (page 36). Refer to the Figure and note the following corrections: B. Near the top of the circuit board are two 47 ohm resistors, both labeled "R314". The resistor on the 1eft is R314 while the resistor on the right should be labeled "R315". b. The polarity marking for diode D302 (1N270) has been omitted. Proper orientation of this diode is anode to the left and cathode (bar) to the right; the arror^r of the diode symbol should point TOI^IARDS 0A302. connector f ingers ttyrt and tr11tt is interc. The labeling of edge tt11tt is the bottom f inger and ttytt is next to changed. Finger the bottom. DO NOT START ASSEMBLY OF THE KIT OR ATTEMPT CONNECTION OF THE WIRED UNITS BEFORE TTTESE MANUAL CHANGES HAVE BEEN MADE. Enclosures, July 25, 1975 5T-6 Manual Up-date: . Page 10 (7 175) New Text Page lL (7 llS) Figure 1 Plug Connectl-ons for Printer, Scope, and AF Input Page LZ (7175) Figure 2 Plug Connections for Key, FSK, and Remote Page L2A (7/75) Flgure 2A Preparation of Plugs Page 13 (7 /75) New Text Page L4 (7 175) Figure 3 Interconnectlons from the 5T-6 to Other Equipment (7 Figure Page 16A / 7 5) 3A Page 168 (7 175) Figure 38 Page 18 (7 175) New Text Figure 3C Connector Orientation on Rear Panel Page 18A (7llS) (7 Page 27 /75) Figure 5 5T-6 Circuit Boards 1 and 2 (7175) Figure 6 5T-6 Circuit Boards 3, 4, and 6 Page 28 Figure 7 5T-6 Circuit Board 5 Page 29 (7 llS) Page 30 (7 175) Figure 8 5T-6 Wiring Diagram Page 44 (7 175) Revised Parts List Page 45 (7 175) Revised ParEs List Revised Parts List Page 46 (7 llS) These pages have been inserted in the manual. ADDENDUII T0 5T-6 OI^INER"S I'IANUAL LZl79 5T-6 Oi^JNER: PLEASE NOTE THE FOLLOWING CHANGES IN YOUR OWNERf S I'IANUAL. (l) On page 22, section 3 under'rAlignment of the 5T-6r" the third sentence states that you should check to see that the AC pilot light and space lamp glow. This should be changed to indicate that only the pilot l-ight should glow at this point in the test procedure. Accordingly, delete the words 'rand the space lamp.tr (2) Refer to the large circuit diagram, drawing No. B9158, dated August 8, L972. Note that the installation of terminal strip C on the front panel will require that the mounting tab (foot) attached to terminal lug seven (7) be cut off. Failure to cut off this mounting tab may result in an equipment failurer or a shock hazard if the tab were to ground out the meter switch. (3) Also in the drawing referred to above, note the two 0.001 uF disc capacitors (C8,C9) shown mounted between each of t.he scope outputs and ground (between pin one and ground and between pin three and ground). THESE CAPACITORS SHOULD BE DELETED. CONTENTS INTRODUCTION 1 SPEC IF ICAT IONS 2 OPERATION 6 15 5T-6 KIT CONSTRUCTION ALIGNMENT AI{D TESTING SCHEI'{ATICS AI{D CABINET WIRING DIAGRAI'{S CABINET AI.ID CIRCUIT BOARD PHOTOGRAPHS PARTS LIST 20 26 31 43 ILLUSTRATIONS Figure 1. Plug Connections for Printer, Scope, and Ar' Input . . . . Figure 2. Plug Connections for Key, FSK, and Remote Jacks . . . . . F igure 3. Interconnections from 5T-6 to Other Equipment . . . . . . Figure 4. Toroid Atignment Techniques . . . . . . . . . . . . . . . Figure 5. 5T-6 St Circuit Boards 1 and 2 (schematic) '. . . . . . . Figure 6. 5T-6 32 Circuit Boards 3, 4 and 6 (schematic) . . . . . . Figure 7. ST-6 53 Circuit Board 5 (schematic) . . . . . . . . . . Figure 8. 5T-6 I^I1 Cabinet Wiring Diagram Figure 9. Circuit Board No. 1 850 Pictorial Figure 10. Circuit Board No. 1 170 Pictorial Figure 11. Circuit Board No, 2 850 Pictorial Figure 12. Circuit Board No, 2 170 Pictorial Figure 13. Circuit Board No. 3 Pictorial Figure L4. Circuit Board No. 4 Pictorial Figure 15. Circuit Board No. 5 Pictorial Figure L6. Circuit Board No. 6 Pictorial Figure L7. Cabinet Pictorial Figure 18. Cabinet Pictorial F igure 19. Cabinet Pictorial aaaoaaaaaa 11 L2 L4 20 27 28 29 30 32 33 34 35 36 37 38 39 40 4L 42 INTRODUCTION The model 5T-6 RTTY Demodulator is a high-performance, all solid-state demodulator for the reception of radio teleprinter RTTY signals. The ST-6 features separate pre-limiter bandpass filters and linear discriminators for reception of the standard 170 Hz and 850 Hz frequency shifts. The input Limiter stage is capable of a dynamic range exceeding 80dB with negtigible zero-leve1 cross-over distortion. An automatic control holds the ST-6 in the mark condition when non-RTfY signals (such as voicer cw, or noise) are received. An anti-space control protects against continuous signals on the space frequency. The motor-controt circuit switches the teleprinter motor on automatically when RTTY signals are detected, allowing fu11 unattended autostart control of the teteprinter for monitoring net frequencies. The low-voltage supplies of the 5T-6 are electronicatty regulated and a L75 vo1t, 60 ma loop supply is incLuded in the demodulator. Normally supplied for use with 120VAC, 50-60 Hz power sources, the 5T-6 can be modified for use with 240 vac power systems by rewiring connections to the por^rer transformer. The complete demodulator is housed in a 3 3/4 x L7 x L2 cabinet and weighs LZ lbs (18 tbs shipping weight). Complete specifications are Listed in the following section. The manual contains compLete operating instructions and a guide to servicing your 5T-6. The construction procedure for 5T-6 kits is also included. Whether your 5T-6 comes in kit form or factory assembled, it will be worth your time to read this manual carefully before operatlng your demodulator. 2. SPECIFICATIONS Input Frequencv Range: 2000 3000 Hz Input Impedance: 500 ohms, unbal-anced Input Bandpass Fllter Bandwldth (-3dB): 1100 Hz (850 Hz shlft) 260 Hz (L70 Hz shlft) Input Llmlter Stage Performance: (Measured wlth a 2L25 Hz slgnal on lnput of denodulator) Llmltlng threshold: L.0 mV peak-to-peak (llnlter switch ln "oN(trtM)t' pos.) L50 nV peak-to-peak Maxlmum Slgnal Input: 10V Peak-to-peak (llnlter swltch ln "oFF (AlI) " pos . ) (elther llmlter swltch pos. ) Dlscrlmlnator Performance : Nomlnal Ftlter Center Frequencles: 850 Hz Shlft: Mark Space 2L25 s. L 5 Hz 2975 Hz : 5 Hz 170 Hz Shlft: Mark Space 2L25 Hz I 3 Hz 2295 Hz : 3 Hz Dlscrlmlnator Fllter Bandwldth (alL fllters 3dB): L40 Hz (850 shlft) 70 Hz (1ZO shlft) Mlnlmum DetectabLe Frequency Shlf t: 850 Hz L70 Ez 50 IIz 10 Hz Maxlmr.rm Detectable Frequency Shlf t: 850 Hz l-70 Hz 1100 Hz 350 Hz N"e' :iri'ifi:":I:::T::iit.:il.;?:"r::hH,i:fi;:l[].1::.i;;;*: between L1,00 Ez and 200 Hz, the tones selected; 1. e. , for shlf ts shoul-d be centered on 2550 Hz; for shlfts between 200 Hz and 10 Hz, the tones should be eentered on 22L0 Hz. Autoprlnt or autostart operatlon ls restrlcted to shlfts wlthln the autostart bandwldth glven below. Autoprlnt Perfoqmance Autostart Response Time: SLow - 3.5 sec Fast 1.5 sec Motor Control Delay Tlme: 30 sec. nomlnal Aurostarr Bandwldth: 850 Hz 140 Hz 170 Hz 70 Hz Autoprint Operation When no RTTY signals are recognized the autostart system ptaces the demodulator in a standby mode with the printer motor and toop current defeated. Within 3.5 sec. (or 1.5 sec. in ttp"sgtt mode) after recognition of a valid RTTY signal, the autostart system energizes both the motor and loop supply and a11ows the demodulator to key Ehe loop. WiEhin 3.5 sec. (or 1.5 sec. ) af ter loss of s ignal, the system is placed in a "mark-holdf condition with loop supply and printer motor energized but with Ehe loop keying stage defeated. If a signal is not recognized within a nominal 30 seconds, the printer motor is shut off and the loop current is interrupted to minimize standby power consumption. The autostart activation is sensed from the discriminator stage and is therefore frequency sensitive. As noted above, the autostart system is designed to work primarily with signals of standard frequency shifts (850 and 170 Hz) and should be defeated when print of non-standard shifts is desired. r Lowpass Filter Stage: Cut-off Frequency: 27 Hz (60 wpm, 45 baud) 45 Hz (100 wprr 75 baud) The low-pass cut-off frequency is normally set at the factory for 75 baud to permit use of the 5T-6 at speeds of 100 wpm. Automatic Threshold Control : This system allows copying of signals on a mark-on1y or space-only basis by providing automatic zero threshold correction. This circuitry functions best when the demodulator is used in the I'FM| mode (limiter on) and offers outstanding performance with a relativety simpte and economical circuit. Outputs: LOOP: Internal L75 vo1t, 60 ma loop supply; Printer selector magnets and transmitter contacts wired in standard series toop, connected to 5T-6 with a L", Z-ci-rcuit ("stereo'r) phone jack. When the ttfiugstr ttStandbytt switch is in the Itstandbyrr position, the keyer stage of the 5T-6 is defeated and teleprinters can be used in rtlocal-looprt configuration. Grounding the trremoterr jack also places the demodutator in ttstandbyrr condition for loca1 loop operat ion. FSK: A low-voltage keying source is provided at the FSK jack for driving FSK or AFSK keyer stages for transmission of RTTY signals. This feature is normally used in 1ocal-1oop mode when transmitting (5T-6 in 'rstandby" mode), but the keying voltages are available at all times allowing the 5T-6 to be used in repeater operations, This output is EIA (RS-232) comparible and is used to drive the HAL RVD-1002 Visual Display system. Nominal Voltages: Mark: -15 V (into a lK load) Space: *15 V (into a lK toad) I(EY : sc'PE' A te legraph key may be connected to the key j ack to provide narrow-shift cw identification when transmitting. When used to key a FSK system, the amount of cw frequency shift is controlled by the I'CW Shift'r potentiometer. :,:fi ;:::il:''ro1",J:"1"': iilH:"i"i::"::::" ":i::.': ::,;I:";:::. is normally furnished with the 5T-6, use of an oscilloscope is optional. ApproximateLy 4 volts peak-to-peak (at the center frequency of each discriminator filter) is furnished to a 1 meg ohm osciltoscope input. Printer: A three-wire, U-ground AC receptacle is furnished on the rear panel to supply po\^7er to tel-eprinter motors. This output is controlled by the autostart circuitry. Total load should not exceed 10 amperes. Note: Fuse protection for this putput is not provided in the 5T-6 each teleprinter should be fused. Miscellaneous Data: Fuse Protection: AC Power Input 0.5 amp. panel mounted fuse holder + L2 v supply 0.25 amp, mounted on power supply circuit card L2 V Supply 0.25 arp, mounted on pornrer supply circuit card Loop Supply 0.1 amp time detay, mounted on power supply circuit card Power Requirement: L201240 VAC, 60 Hz (norma11y provided for LzO VAC unless otherwise specified 240 V plug to be supplied by user) Power Consumption: 7 watts maximum "Standbyrt configuration (Loop off) LZ watts maximum ttReceivett mode, Loop or1. Voltage Tolerance: * L0% Mechanical: Size : 3 3/4,, high X LZn deep X L7,, wide style: Table-top cabinet or standard 19tt relay-rack mounting. Weight: 18 1bs., shippirg; L2 lbs. net. color: Light gray front and rear panels with dark gray wrinkle finish top, bottom, and side panels. 3. OPERATION The 5T-6 is one of the most elaborate RTTY terminal units offered to amateur radio operators. It incorporates many features which when properly understood and applied, can add much to your enjoyment of RTTY operation. The following discussion is a general guide to the use of these features and should be partlcularly helpful if you have not had experience with the advanced autostart circuitry first introduced in the TTlt and TT/1,-tf RTTY terminal units. As you gain familiarity with the 5T-6, you will probably develop your own preferred techniques for operation. Tuning a Radio Teleprinter Signal for Optimum Performaqge forms of tuning indicator are provided for in the HAL 5T-6: the familiar crossed-e11ipse oscilLoscope display and a tuning meter. The reter is included in the 5T-6; a jack on the rear panel is provided for connection to an external oscilloscope. Both techniques provide retiable indications and are considerably easier to use than describe! Two different I{hen using the oscilloscope as a tuning indicator, a portion of the signat at the mark filter of the discriminator is coupled to one of the inputs of the scope (usually the horizontal input) and the signal at the space filter hlhen the receiver is is coupled to the other scope input (vertical). properly tuned, the mark signal witl produce a line or ellipse in the horizontal plane, and the space signal a tine or ellipse in the vertical p1ane, If the received signal has the sarrn shift as the TU discriminator, the two displays will be maximum amplitude at the same frequency on the receiver. The receiver is therefore tuned for a maximum in both lines. The discriminator in the 5T-6 uses fairly broad bandwidth tuned circuits to achieve a linear response and therefore the scope patterns will be elllpses instead of lines. trIhen tuning, adjust for maximum amplitude of the major axis of each ellipse and ignore the minor axis or width of the ellipse. The ellipses for the L70 Hz filters wilt be wider than those for 850 Hz shift. straightforruard, although it will require some time for RTTY enthusiasts familiar with the scope display to adapt to this. The signals from both the mark and space filters of the discriminator are detected and combined to produce a DC voltage that is positive for either tone (the I'plus-plust' voltage). The voltage on the rrplus-p1us" line is therefore a direct indication of how close the received signat is to center This voltage will be a maximum when the received frequency of each filter. mark tone is correctly centered on the mark filter in the discriminator; the sarre applies to the space tone. Use of the tuning meter is The discriminators of the 5T-6 are preadjusted so that the maximum voltages from the space and mark filters are equal. Therefore, if a signal is tuned in so that both its mark and space signals are centered on the 5T-6 discriminator filters, the voltage on the 'rplus-plus" line wilL be a maximum for either tone, and in fact, will not change as the signal goes from mark to space and back. Thisttplus-ptusttvoltage is indicated on the tuning meter, Correct tuning on the meter is therefore indicated by maximum deflection that does not vary as the incoming signal switches back and forth between mark and space. will be if the signal is not tuned correctly; if tuning is set so that more output occurs from one fitter than the other, the tuning meter may not read maximum deflection and wilt definitely flicker when the signal goes from mark to space. If no RTTY signal is present, the tuning meter will not read as high and wilt flicker widely on the incoming noise (for the present discussion, any interference such as CW or SSB is also considered to be noise). Now consider what the meter indication If the received signal is transmitted with a frequency shift sonewhat different from the standard 850 or L70 Hz shifts provided for in the 5T-6, it will be impossibte to adjust the receiver for maximum deflection of the meter with no flicker, since it is impossible to get both tones centered on both filters at the same time. However, the 5T-6 will very reliably copy shifts considerably narrohTer than the design center by straddle-tuning the signal. This is the primary reason for use of the linear discriminator. adjust receiver tuning for minimum flicker of the tuning meter. This receiver setting will not produce ma>timum deflection, but the demodulator will sti11 perform properly (except for the autostart circuitr ds will be discussed later). The tuning meter driver circuit is adjusted so that a RTTY signal with proper shift and correctly tuned will produce a meter deflection of 0.7 ma in the 850 Hz shift mode and 0.6 or higher in the L70 Hz mode. hlhen straddle-tuning a signal, With either type of indicator it, is best to defeat the autostart circuitry when tuning by placing the "AUTO - AUTO OFF'i switch in the "AUTO OFF'| position. Although the 5T-6 will reliably print very narrow shifts, the autostart imposes rather tight tolerances on the shift to minimize unwanted turn-onts. It is also best to tune in stations with the limiter set to "ON(FI"I)'i and then go to limiterless operation "OFF(AI"1)" if necessafy to copy through interference The ST-6 Autostart System The autostart system in the 5T-6 is considerably more complex than those circuits normalty added to terminal units to simply turn the printer motor on and off. Two independent functions are controlled in the 5T-6 the keyer stage operation and the power to the printer motor. Controt of the keyer stage provides a fairly rapid means of placing the printer in mark-hold condition while keeping the motor on for a predetermined length of time. This feature is particularly convenient when in QSO, since the machine prints littte garble between the end of one stationrs transmission and the beginning of anotherrs. Properly adjusted, the autostart is even immune to the stationr s CW identification (if narrovr-shift CW ID is used). If a RTTY signal is not received within 25 to 50 seconds (the exact time may vary between units because of electrotytic capacitor tolerances) after a station ceases transmitting, the printer motor is shut off. The keyer and printer motor are re-activated automatically whenever a signal is received (within 3-4 seconds in 'rSLOWr mode, and approximately 1 second in "fASTrr mode). is triggered from the sanre rrplus-plus'r line used to drive the tunlng meter. A threshold level adjustment (the trim-pot on circuit board 4) presets the voltage required to trigger the autostart. Since the amplitude of the I'p1us-plus" voltage is proportional to frequency, this adjustment also sets the shift-frequency tolerance of the autostart trigger point. If the trigger threshotd is adjusted close to the maximum voltage available from the plus-plus line, the autostart will trigger only on strong signals with exactly 850 Hz shift. If it is adjusted too far the other waY, the autostart will never deactivate. The autostart circuit The autostart trigger threshold is normally adjusted to trigger on any signal that gives a tuning meter indication of 0.6 ma or higher, but you may wish to experiment with this adjustment to determine the trigger level you prefer. Set at the 0.6 ma leveI, the autostart will respond to signals within approximately +100 Hz of 850 Hz shift and *45 Hz of L7O Hz. This tolerance becomes considerably tighter for weak signals. is that when power is remotor, the loop current of the 5T-6 is removed by shorting the base of the keyer transistor to ground. This reduces the power consumption and heat generated during stand-by periods. An additional feature of the motor control circuit moved from the printer There are four toggle switches and two pilot lamps which control and monitor the operation of the ST-6 autostart circuits: SLOW FAST: This switch controls the turn-on time of the autostart system. In the "SLOW' position a RTTY signal must be present for approximately 3 to 5 seconds (5 or 6 characters) before the autostart witl actuate. This delay provides fairly good protection against false turn-onrs. The rrFASTtt position allows the TU to activate in less than a second, particularly conveni-ent for fastbreak operation. The motor relay and therefore the printer motor are held on whenever the switch is in the trFASTrr position. AUTO - AUTO OFF: This switch defeats the ]utostart circuitry for tuning or for ful1 manual operation. AIITO STANDBY: In the "STANDBY'i position, the 5T-6 is tocked in a mark-hold condition with the printer motor or1. Received signals will not be printed but the tuning indicators wilt stitl function. This control is quite convenient for use when transmitting. It is paralLeled by the remote jack on the rear panel so that it may be connected to station transmit-receive control circuitry. AUTO MOTOR: In the I'MOTOR" position, the printer motor control feature is locked out and the printer motor is held on. RECEI\IE: This pilot tamp will f.ight whenever the autostart has activated the TU for reception of RTTY signals. STBY: This pilot lamp lights whenever the autostart is not active and the printer is belng hetd in the rnark-hold condition or when the motor has been turned off. Note: Both the "RECEIVE" and rrSTBYrt lamps will be lit whenever the '|AUTO'' "STAI.ID-BY'r switch is in or when the remote jack is shorted. This provides a positive indication that the TU is in the standby mode and serves as a warning that the TU will not receive signats. ITSTAI{D-BY!! position As discussed previously it is usually easiest to tune the receiver with the autostart defeated until you have become familiar with autostart operati.on. The time delay generated by the autostart, particularly in the "SLOW" mode, can be particularly disconcerting if you expect to get print-out immediately upon achieving correct tuning. Autostart operation is most useful for monitoring net frequencies and during QSOrs, particularly in round-table discussions. The ST-6 Anti-space Circuit The 5T-6 includes a circuit that prevents the printer from 'rrunning open" if a continuous space tone is received, The circuit senses the length of time that a space signal is present at the output of the slicer stage. If it exceeds the maximum possible time permitted by the Baudot (RTTY) code (L32 ms for a btank k"y), the keyer stage is placed in mark-hold condition, 3S in autostart operation. Also, the output of the anti-space circuit is coupled to the autostart circuit so that the motor is shut-off if the space condition persists. The anti-space mark-hold feature is always active in the 5T-6. Other Controls The functions of the remaining controls on the 5T-6 are as follows: SHIFT (170 850): Either of the two standard RTTY shifts is selected with this switch. It connects the correcE input filter, limiter, discriminator, and low-pass filter section for the shift to be demodulated. It also switches the plus-plus line from one discriminator to the other, and the AK-1 AFSK osciltator, if used. On demodulators with the 3-Shift dptionr- a third switch position setects 425 Hz shift. LIMITER (OFF(AI,I) - ON(nq)): The input amplifier can be switched from limiting operation to a linear amplification mode with this switch to a1low limitertess reception, sometimes useful in copying weak signals through interference. The switch controls the limiter stages for both 170 and 850 Hz shifts. The autostart circuitry is automatically defeated when the switch is in the ''OFF(AM)" posit ion. NORMAL - REVERSE: This switch reverses the input to the slicer stage for copying signals wi th reversed shift. For reception of tm FSK signals in the "NORiu111'' position, the receiver should be used in the lower sideband mode. VHF AFSK signals should copy in the "Noniq1tr" position lf the convention of low-tone mark is followed, In rhe "TUNING" position, the meEer functions as a tuning meter, BS discussed previously. In the "LOOP" scale of 0-100 fta, it monitors the loop currenE. METER (TUNING LOOP (100 ma)): MARK SPACE: These two neon pllot lamps indicate the conditlon of the They normally flash when receiving RTTY slgnals. loop circuit. good for impresslng visitors to the shack, particularly They are people used them for tuning indicators. have although some ON OFF: This switch controls all poe/er supplies, lncluding the loop supply. The printer motor potrer is not directly conErolled by this switch but cannot be activated with the 5T-6 off, since Ehe motor relay controls the Printer motor. 0.5 AMP: Thls is the AC fuse for all power supplies ln the 5T-6. It does not protect the printer motor since the motors are usually fused in the printer housLng itself. CW SHIFT: When using the Malnline FSK keyer system, thls potentlometer adjusts the shift for CW identlfication. External Connections The followlng rear-panel connections are provlded on the 5T-6: The audio ouEput from the statlon receiver should be connected to this jack. Use the receiver's 500 ohm audio output tf at all possible. A 1ow impedance output will work, but will reduce the porenrial limiting by some 30 dB. Volce-coil to 500 ohm llne transformers are available at reasonable cost and are a worthwhlle investment. The receiver volume need not set very hlgh' partlcularly if the 500 ohm ouEput is used. See Flgure 1 for connectlon detalls. AF IN: SCOPE: An external oscilloscope can be used as a tunlng lndlcator by connectlng the vertical and horizontal scoPe inputs to the three pin connector on the rear panel of the 5T-6 . Usually, the !'lark signal (pin 1) is conneeted to the horizontal input and the Space signal (pln 3) is connected to the vertical input of the scope. Use a length of two conductor shielded cable to make thls connectlon with the shield connected to pin 2 of the scope connector and to the ground of the scope. Preparation of the connector pins ls shown ln Figures 1 and 2A. Be sure that the pins are installed ln the ProPer location in the conitector shell. REMOTE: An exterrral switch or set of relay contacts can be connected between pins 5 (ground) and 6 of the Control connector to provlde renrote standby control. The 5T-6 will demodulate slgnals and drlve the printer when there is an open circuit beEween plns 5 and 6. When the pins are shorted together, the 5T-6 output ls held ln mark-hold condition. This feature allows automatlc control of the 5T-6 by the transmit-recelve circuitry of Ehe statlon. Preparatlon of Ehe connector pins is shown in Figures 2 and 2A. 10 (7 l7 s) 2.WIRE CABLE (ANY LENGTH ) -l I I PRINTER I SELECTO R LOOP TYPICAL MAGN E TS rrY MACHTNE JUMPER OR ADDITIONAL TTY EQUIPMENT I I llm jErYg.rrr^.r: I L MARK MARK I I I -J TO HORIZONTAL INPUT GND SPACE SFACE 2-CONDUCTOR SH I ELDED CABLE (4f MAXIM UM LENGTH ) OSCILLOSCOPE CONNECTIONS t SCOP E TO VERTICAL TNPUT ourPl? Ul'f.38,r.* SHTELDED CABLE : (AtlY LENGTH ) AUDIO IN PUT 500 n To 4n TRANSFORMER ll _ E ll ! II ro 4n AF ourPUT oN RECETVER (SPEAKER TERM rNAL) I: Figure I Plug Connections for Printer , Scope , ond AF Input 11 (7 I 15\ bJ^ i< oilg Ll-, o ?r 3v () . J Fp =T;o (J=- >o a2p lrJ 11 E= i=Y l-(, l-t//(JL lrj < zZ,E, oo >o ()LL (l) o E o lrJx YI PA E. FY o (r) lr- trJ 65 oo tduJ Jn (Dt.t trt E c(, 3E f z. (i) IJ- :< O(r J l! =o fi,2' )< CJ) UJF (l) o o C o rF J o E, lr, ? F o F ..(, llj zo lrJ - G xdq E< ()o=- ?o5 o-x ?E= Gl- () F - (l) c c o () (J !l trt E ol f :E o- frf b J- rq o- A+$ -= ts= Jy t-r i lrJ < U)+ == \t [r v 9ro 2 r-o >Xo hJ v: Yr-A v5> A <:E L1C eo{ F- r L2 (7 /7 s) N ' (l) :f .9 tL INSERT PIN CONNECTOR BLOCK LOCKED Figure ?o Preporotion of Plugs 12A (7 li 5) KEY: A key can be connected to the Control jack for CW ldentlflcation with either narrow-shlft AFSK (wirh rhe AK-l or XTK-100) or with a Mainline FSK system. The key should be normally open. For AFSK cw identification, connect the key between pins 4 and 5 (ground). For FSK cw identification, connect the key between pins 1 and 2 (ground). See Figure 2 for connection details and Flgure 2A for preparation of the connector pins. FSK: The keying voltages provided at this pin on the Control connector are fu11y compatible with the Mainline FSK keying system. For a full dlscussion of a FSK system, see Hoff's article in May, 1965 QST, page 16. The FSK output can also be connected to the Voltage (or EIA) Input on the HAL RVD-1005. See the RVD-1005 manual and Figures 2, 2L, and 3 for further details. LOOP: Connect the RTTY printer and other RTTY equipment to this connector. Normally, the printer and keyboard of a machine are series connected at the machine and the two wires then connected to the plug. If only one piece of equipment is to be connected to the 5T-6, connect it to pins 1 and 3 of the loop connector and place a jumper wire between pins 4 and 6. An additi.onal machj-ne can be connected to pins 4 and 6 in place of the jumper. Cables from the printer and keyboard should be wired as shown ln Flgure 1. No portion of the loop should be connected to ground. PreparatLon of the vartous connectors is shown in Figures J-, 2, and 2A, Typical interconnec t ions between the 5T-6 and other RTTY equlpment are shown in Fi-gure 3. . NOTE: The plns cannot be eaally removed from the plug shells after they have been Lnserted. Refer to Flgures 3C (page 18A) and 8 (page 8) as well as to the markings on the exterLor of the rear panel to make sure that connectlon ls made to the proper plns BEFORE lnserting them lnto the plug. MOTOR: If the power cord of the prlnter ls'plugged into thls connector, the 5T-6 autostart clrcultry rr111 automatlcally'turn the printer motor on and off. Note.that a three-conduetor grounding socket is provlded. It ls strongl-y recomnended that the prlnter motor be equipped irith a groundlng power cord and that the frame of the prlnter be flrmly attached to a good electrlcal ground. AC POWER CORD: A standard three-wlre grounding power cord is furnished rf ith the 5T-6 for connection to 115 / 120 V, 60 Hz power mains. ALWAYS OPERATE THE ST-5 WITH AN ADEQUATE GROUND. FAILURE TO GROUND THE UNIT OR DETEAT OF THE POWER CORD CROUND VOIDS THE WARMNTY. When operatlng the ST-5 from a 230 V power 1ine, be sure that the transformer primaries are properly connected and that the proper plug is installed on the power cord. Agaln, the 5T-6 nust be properly grounded. 13 (7 /7s) lrJ o lr) (I) I (9 C) (E o o lrJ OF tr, i rA c (D lrJ oE t5 o (E E .g = 5 (n t lrJ X> o Eik Io.rI, -c >=2.lrJ - (D E L o) o(/,:uJ o (ts lrl E(9 tI^ CE, 5 cd l-o- ldF !,r P2 =F. >D 6O Ef = o o<F F3 @ figi F I a o ?: H: E o o l! Qd i= lr.l oFaO zoo E,J o-t F l oF D o Y o lL 5 (J L U' z uS ffio >F (ts o F o(J -o r 9 o @1 tJ $I irr (D I B = o Y o ---l o c .9 o o c c o o L (l) c rO lrj (l) L o- o o ct, = .9 l.t. FY Itl r FJ t?o *J -2, r.o U)t =fl pE L- (9 :) oa r- oo EF pl =p oo -a f fiH o- O-J o o J (E UJ F ' (r) o- 9E oh 2u zo =c) Sa 14 (7 /7s) 4. ST-6 KIT CONSTRUCTION The HAL Communications Corp. ST-6 parts kit furnishes the experienced RTTY enthusiast with quality parts at a reasonable price for the construction of the 5T-6 RTTY Terminal Unit described by Hoff in September and October, L970, RTTY Journal, and January and February, L971, HAM Radio. To provide for all features of the terminal unit, a set of seven printed circuit boards and associated components are furnished. This is not a kit in the usual sense; step-by-step instructions are not furnished, It is assumed that the builder has experience in electronic construction and can build from schematics and pictorial layouts with a limiEed amount of suggestions. This is NOT a kit for beginners to undertake: A few hetpful hints regarding circuifEoard construction in particular are included, but a number of details are left to the inventive mind of the builder. The parts for the 5T-6 have been packaged with all resistors in one sack, all capacitors in another, etc. Upon receipt of the parts kit, the builder should unpack ALL components and separate them according to the individual parts lists .for each circuit board. Notify HAL Communications Corp. immediately of any shortages so that we may promptly rectify the problem. A11 components are covered by the standard HAL Communications Corp. one-year warranty. If a failure occurs, please write giving full details. DO NOT ship any item back without prior notice to HAL Communications Corp. The following pages of construction techniques are a collection of hints for the construction of the circuit boards and placement of parts and boards in the cabinetry. Please read the entire manual before starting construction. Construction of. Circuit Boards The pictorial layouts show the placement of the components on the boards. The Molex Soldercon terminals for the integrated circuits should be inserted and soldered to the board first. The Soldercons are supplied in 7 pin strips, two per integrated circuit. DO NOT remove the individual pins before soldering the strip in p1ace. Insert all Soldercon strips at the appropriate positions and solder them in p1ace. Use great care in sotdering to prevent solder from flowing inside the pins and from bridging across the closely spaced pads on the circuit board. After all the Soldercons for a given board have been soldered in place, the ftcarrierrrstrips are removed from between the pins by gripping the carrier strip firmly with longnose pliers and bending gently in a dornmward direction away from the pins. There is a pre-formed indentation along the carrier at each pin so that the carrier will snap off without too much force. Be careful not to bend any of the terminals when removing the carriers. The integrated circuits can now be inserted in the Soldercon terminals - be sure to position the rrurr-shaped indentation on the top of the IC at the proper end as indicated in the pictorials. The resistors should be inserted next. are inserted vertically. When installing 15 Unless otherwise noted all resistors vertically mounted components, place the component body as shornm in the pictorial. Solder the resistors as they are installed. The capacitors should be installed next. Be sure to observe polarities on electrolytics, It is good construction practice to orient components so that their labels can be read easily after the board is constructed Semiconductors (other than the ICs) can now be mounted; avoid overheating the germanium diodes. A11 diodes are mounted verticalty. Make sure that transistor orientation agrees with the pictoriaL drawing, and observe diode polarities. Larger components, such as toroids, trim-pots, and the electroLytics on boards 4 and 5 are mounted last. It is much easier to adjust the tuned circuits before they are mounted on the circuit boards. A good procedure is to construct aL1 other portions of the circuit boards and then tune all ten toroids as a final step. Tuning procedures are discussed later in the manual. A few specific hints for the construction of each board are listed belor^r. circuit Board No. 1 - Filter/Limiter (Figures 5, 9 and 10) The layout shown in Figure 9 applies to the 850 Hz shift filter-limiter board; that shown in Figure 10 applies to the 170 Hz shift board. Five extra pads are provided on the circuit board for use in trinming the tuning capaciiors to the correct values (C102A, C104A, C106A, C107A, C108A on board t-aSO and cL52A, ct54A, c156A, cL57A, c15gA on board 1-170). The 22 mHy inductors required for the L7O Hz shift filter are derived by paral1el-connecting the two windings of the toroids in paraLlel-aiding (rtLoose-endstt tied together and ff tailsrtt or sleeved ends, together). -The 88 mHy toroids for 850 Hz shift are derived by series-aiding connection of the toroi.ds. The toroids are mounted to the board with the 1t6 hardware and large washers supplied. Assemble the hardware as foLlows (from top-to-bottom): screr^r-head, 116 f latwasher, nylon washer, toroid, circuit board , lt6 loclcr.rasi"r, tf6-32 nut. The complete assembly should have the toroid and screw-head on the component side of the board and the nut and lockwasher on the. copper side of the board. An extra ground pad connection is provided for each toroid for greater convenience in connecting the toroids to the boards, particularly when the parallel connection is used. Wtren the series connection is used, a spare, isolated pad (marked rrCTrr) is provided for each toroid center tap. Circuit Board No. . ? - Qiscriminator/Detector/Active Lowpass Filter (Figures 5, Ll and LZ) The board pictorial shovrn in Figure lt is used for 850 Hz shift and that shovrn in Figure LZ is used for 170 Hz shift. Extra pads are provided to aid in tuning the toroids. 16 SINGLE TOROID -r I <--TOROID RETAINER (rHnEaoe o) I tt tt ,t COMPONENT TOROID 1---- .<..-clRcUlTBoARD ---- #6 LOCK WASHER I COPPER SIDE -<EI EI EI EI F-l l-l a E STACKED TOROIDS :=_- 6_J2 x \tt- -r I +- #, scREw TOROID RETAINER (THNEADED) I \ t I I , COMPONENT SIDE TOROID t CIRCU coPPER srDE TOROID --// NYLON WASHER r/ tt ,i RETAINER IT BOARD \ I :-.---_ roRotD rrrr (NON-THREADE D ) -------------,-/t il\ z]-r\ #6 LOCK WASHER 6- 32 r r *" scREw Figure 3o Toroid Mounting 16A (7 /7s) STAN DARD -oa MULTICOLOR rl(-i ' -\ ":iiL_. OUTER WRAP -\ I .rr\llllrf7, INNER WRAP --, SERIES CONNECTION , 88 rnH h, L=88 ,nX il ll I CT (CENTER TAP) 1l tl L, A 4. PARALLEL CONNECTION , 22mH L=22rrI 1il t //r 7ffiffi