by Robert Kirsch
This article describes the Decoder needed to demodulate the APT (Automatic Picture Transmission) signals trans mitted from most of the orbiting and geostationary weather satellites. These signals can be received using the Receiver described in Part 1 of this series.
The Decoder accepts audio signals either from tape or directly from the receiver and converts them into an 8-bit digital format with necessary synchronizing pulses for connection to a suitable computer or frame store for display on a television or monitor. Controls are pro vided to enable the contrast of the picture to be adjusted and various types of synchronization may be selected to suit different satellites. Power for the decoder comes from an internal power unit which will also supply the receiver.
The APT Format Pictures transmitted by most VHF American and Russian orbiting weather satellites, as well as WEFAX transmissions from the GOES series satellites (e.g. ESA METEOSAT 2), use the APT format.
The radio frequency carrier is frequency modulated by a 2.4kHz subcarrier whose amplitude is modulated by the picture information and synchronizing signals.
Figure 1 shows the subcarrier envelope for a typical line of APT information.
Peak white, it will be noted, corresponds to maximum subcarrier level, and black to the minimum. Picture lines are transmitted either 2 or 4 times a second, each line having 600 cycles of subcarrier, thus the maximum horizontal definition is 600 pixels. The TIROS satellites send alternate lines of infra-red and visible information (when viewing the Earth in daylight) each line being preceded by synchronizing pulses.
Channel 1 (visible) sends 7 pulses at 1040 pulses per second and channel 2 (infrared) sends 7 pulses at 832 pulses per second. Meteosat sends 7 pulses at 840 pulses per second at the start of every line, as well as a 300 pulses per second start and a 450 pulses per second stop signal for frame synchronization.
Decoder with the Receiver
The Russian Meteor satellites send approximately 2 lines per second with a synchronizing tone of 300Hz for every line. The decoder described in this article produces line synchronizing pulses by dividing the 2.4kHz subcarrier digitally, using a programmable divider to obtain the correct periods for various types of satellites. These pulses may be manually adjusted to correctly position the picture on the screen. (When using the optional sync tone decoder card this is achieved automatically.)
Circuit Description
Figure 2 shows a block diagram of the decoder, synchronizing unit and power supply. Figure 3 shows the circuit diagram for the main circuit board. Live or recorded signals, selected by the receiver, enter via the 6-pin DIN socket and are first fed to a master level control.
The signal at this point splits into three paths; the first goes to the A/D converter, the second to the Level Meter and AM detector circuit, and the third to the Phase Locked Loop carrier regeneration circuit.
Figure 1. Typical APT information.
Figure 2. Decoder Block Schematic.
The conversion from the analogue subcarrier level to a digital code is accomplished by IC2, an 8-bit A/D converter. This device requires two inputs, one is the analog information, and the other is a 'start conversion pulse'.
The analog input range of IC2 is from 0 to 2.5 volts to give codes from black to peak white. It is therefore important to adjust the level of the incoming signal in order to obtain correct contrast on the displayed picture. This function is provided by the opamp ICla. The gain of this device is adjusted by RV5 in the feedback circuit, this sets the white level.
The output from IC la is about ±2.5 volts but only the positive half cycle is fed to the A/D converter. RV4 sets the DC reference of the op-amp, and this offset is used to adjust the black level of the picture. Note, there is always a small amount of carrier at black level for synchronizing purposes, so this circuit enables this level to produce true black on the display. The black and white level controls may also be used to enhance pictures particularly when only a few grey levels are available from the computer or frame store used.
The two light emitting diodes LED1 and LED2 are used to obtain the correct setting for the black and white level controls. The most significant bit from the output of the A/D converter is monitored and, when this bit goes high, TR2 turns on and causes LED2 to light, this indicates a level approaching peak white. All 8 bits are fed to the NOR gate IC5. When all 8-bits are low the output of this gate turns TR1 on, causing LED1 to light and indicate black level.
The second op-amp, IC lb, is fed with the incoming signal via the input level control. The output from IC lb is rectified by D3 and D4 to drive the level meter which should read full scale on a peak white signal. The AM detector formed by D1 and D2 is also fed from the output of IC lb and this audio signal is fed to the sync tone decoder card.
The phase locked loop, IC3, is fed with the incoming modulated signal and locks to the 2.4kHz subcarrier. The clean square wave output produced is used to generate the 'start conversion' pulse for the A/D converter and it is also fed to the programmable divider to produce line synchronizing pulses.
Figure 4. Diode Card Circuit.
Figure 5.
The three counters IC6, 7 and 8 form the programmable divider whose division ratio is set by the data on pins 3, 4, 5 and 6 of each IC. The rotary switch S2 selects one of two preset ratios (1200 for 2 lines per second and 600 for 4 lines per second) and also two ratios that may be set by programming the optional diode cards, the circuit of which is shown in Figure 4. The SLIP control, S3, temporarily raises or lowers the division ratio to enable the picture to be moved in relation to the line sync pulse thus shifting the display left or right in relation to the television screen. The phase locked loop will produce an output even when no input is present, and therefore line sync pulses will also occur. For this reason the HOLD switch is provided to stop the counter, thus preventing the current picture from being lost.
Four audio monitor points in the decoder are connected back to the receiver in order to help in setting up and testing. One of these is connected to the 2.4kHz output from the phase locked loop and another to the output of the AM detector. The remaining two monitor points coming from the optional sync tone card.
The preset RV I, along with the TEST LINK are provided to help in testing and setting up the A/D converter, computer hardware and software. This potentiometer provides an adjustable source of voltage to the input of IC la which will simulate signal levels from black to peak white.
Sync Tone Card
This card is used to detect the line synchronizing tone at the beginning of each picture line. Figure 5 shows its circuit, and it will be noted that a MF10 switched capacity filter (IC2) is used to select the tones. The frequency of this type of filter is determined by the frequency of the oscillator fed into pins 10 and 11 of the IC, in this case it is 100 times the required filter frequency. The two separate halves of IC2 have different bandwidths for optimum reception of different types of sync tones. The frequency of the voltage controlled oscillator, IC1, is controlled by the three multi -turn potentiometers RV3, 4 and 5 which are selected by S4 on the front panel.
The input level of IC2 is preset by RV1 and RV2, and the filtered output is buffered by TR1 and TR2. TR3 with DI, 2 and 3 form a threshold switching circuit whose output is used to reset the divider on the main board when the LINE SYNC switch is operated.
--------- Decoder Board
Figure 5. Sync Tone Circuit.
Construction
Referring to the Parts list and component overlay on the three circuit boards, Figure 6 shows the legend of the main decoder board, Figure 7 gives the tracks and overlay of the Sync tone card, as does Figure 8 for the Diode board;
insert and solder all components in the following order: fixed resistors, capacitors, diodes and bridge rectifier, SIL resistors, IC holders, transistors and regulator IC's; vero-pins, preset resistors and finally plugs, sockets and edge connectors. NOTE - observe the correct polarity of transistors, regulators, diodes, LED's, meter, electrolytic capacitors and the bridge rectifier. The white dot marked at one end of the SIL resistor package should correspond to the white dot on the board overlay. The tags of the Minicon plugs should be to the rear of the circuit board. The white rings on the overlays indicate where the boards should be soldered on both sides; in addition TR1 on the sync card should be soldered on both sides also.
Insert the keys into the edge connectors, referring to the wiring dia gram Figure 9. Carefully insert all integrated circuits into their correct holders ensuring that pin 1 marked on the board aligns with pin 1 of the IC.
Carefully fit the clip-on heatsink to REG2.
Use the stick-on front panel as a template to mark out the front plate of the box, before drilling and cutting out, see Figure 11. Remove the protective backing from the front panel and carefully position it on the prepared front plate, pressing down evenly all over, making sure there are no air bubbles trapped underneath. Mount all controls and switches on the front panel. Referring to the wiring diagram Figure 9, connect all level controls, toggle and rotary switches, LED's and the meter to their appropriate Minicon housings via the ribbon cable provided, allowing approximately 5 inches of cable from each housing to the front panel. Note that the Minicon housings will have their lugs towards the rear of the circuit board when installed. (Refer to the Receiver article for details of how to make terminations to the Minicon connectors, Maplin Magazine Issue 18.)
Figure 6. Decoder PCB Overlay
Figure 7. Sync Tone Tracks and Overlay.
Figure 8. Diode Board Tracks and Overlay.
Figure 9.
Figure 10. Power Supply Circuit.
Mount the toroidal transformer with the rubber washers provided on either side and place a solder tag under the fixing screw, the PSU circuit is shown in Figure 10. Insert the rubber grommet into the hole in the transformer bracket and pass the red, blue, grey, and yellow wires from the transformer through the grommet. Referring to Figure 11, mark and drill the base plate and mount the transformer bracket, placing the mains label in a visible position on this bracket.
You can make your own bracket if you wish according to the dimensions shown in Figure 12. Drill and cut out the rear plate of the box and mount the fuse-holder. (Check that when the case is finally assembled, the fuseholder tags will be clear of any obstructions.) Pass the mains cable through the strain relief grommet and then through its hole in the rear plate and secure grommet in position, then referring to Figure 9, connect the brown wire via the fuseholder to the mains switch. The blue wire connects straight to the mains switch and the green/yellow wire to the earth tag under the transformer mounting screw. Terminate the two orange primary wires from the transformer at the mains switch. Insulate all exposed mains connections. Fix the main circuit board to the base plate, and solder the trans former secondary wires onto their respective pins.
The case may now finally be assembled and the front panel connectors plugged onto the circuit board.
The decoder is now ready for testing.
Setting -Up and Testing WARNING - Take care when working on the decoder with the mains supply connected. NOTE - Do not connect the computer, frame-store or receiver until the following tests have been carried out.
--------------above: Sync Tone Card; Diode Board
Figure 11. Case Cst-ost Details.
Figure 12. Transformer Bracket.
Figure 13. Sync Card Frequency Settings.
----------- 14
Set all three front panel level controls anticlockwise. Insert the 1 Amp fuse and connect the Decoder to the mains supply. Switch on. The mains indicator light in the power switch should glow and the red 'Peak Black' LED should be illuminated. Using a suitable multi-meter check the power supply outputs at the test points provided to obtain the following readings (to within ±0.5 volts).
All readings are relative to 0 volts (TP4) or chassis. TP1: +12 volts, TP2: +5 volts, TP3: - 12 volts.
If these readings are correct, connect the Decoder to the parallel 110 port of the computer/frame-store and run the appropriate software. (When using the Amstrad or BBC software provided in this article, set the horizontal resolution to 4.) Set the TEST preset (RV1) fully clockwise and the sync switch to SCAN. The lines per second switch should be set to 2. Join the two TEST LINK pins (PL1) together and note that the ' Black Peak' LED remains alight.
Slowly rotate the TEST preset anti clockwise whilst observing the monitor screen. The brightness of the scan lines moving up the screen should be seen to progressively increase as the control is rotated. Repeat this test and note that the 'Black Peak' LED goes out before the first grey level appears on the screen and that the ' White Peak' LED comes on as the maximum white is approached. When the full number of grey levels appear on the screen move the scan switch to `HOLD' (this should stop the picture being scanned) and check that the correct number of levels appear on the screen depending upon the type of display system in use. (The Amstrad and the frame-store should produce 16 levels including black and white, and the BBC 8 levels including black and white). The 'TEST' link pins may now be disconnected.
The following tests should be carried out by using a good quality recording of the NOAA 6 or NOAA 9 satellites. Connect the Decoder to the Receiver via the 6 -way audio DIN lead and the power lead. Connect the tape recorder to the Receiver, referring to the previous article (Issue 18). Play the recording of the satellite. Select TAPE OUT on the MONITOR switch of the Receiver and adjust the VOLUME to a comfortable level. Set the Decoder INPUT LEVEL control to minimum.
Switch between TAPE OUT and PLL on the MONITOR switch, and adjust the preset RV2 on the Decoder board until the tone from the PLL is the same as that of the satellite's subcarrier.
To check this setting, the INPUT LEVEL may now be increased and the 'Black Level' LED should now flash or go out. Check that the LEVEL meter responds as the INPUT LEVEL control is increased.
The basic Decoder is now ready for use but if the sync tone card has been installed the following setting-up is required. The three multi-turn presets on the tone card are best adjusted using a frequency counter, with reference to Figure 13. Where no frequency counter is available, this adjustment may be carried out by using the audio monitor test points provided in the Receiver unit in the following manner.
When playing a recording of the NOAA satellites, the characteristic 'clip-clop' of the synchronizing tones will be noted. The first two positions of the LINE SYNC switch (TIROS') select one or other of these two tones, the third position is for the Russian Meteor satellites.
Play the recording as before and adjust the INPUT LEVEL to give about half scale on the LEVEL meter. Select the first position of the sync detector on the MONITOR switch. Switch the LINE SYNC switch to TWOS 1, and set the two presets RV1 and RV2 on the sync card to their mid -position, and adjust RV3 to obtain the loudest output for the higher tone.
Repeat this procedure with the LINE SYNC switch set to TIROS 2, and adjust RV4 to obtain the maximum output for the lower tone (RV5 may be adjusted in the same way when playing a recording of a Meteor satellite with the SYNC switch in the METEOR position).
Switch to the second sync detector position on the MONITOR switch and adjust RV2 on the sync card to obtain a short burst of noise that corresponds to every second sync tone of the recording.
Check this setting in the other (TIROS) position of the SYNC switch. For the METEOR position of the SYNC switch, adjust RV1 to obtain the noise burst for every sync tone when playing a recording of the satellite.
Decoder in Use
The following information refers to the use of the decoder with the BBC B and Amstrad computers. (Information for using the Frame Store will be published later).
Figure 14. Settings for Russian Satellites.
Program 1 is for the BBC model B, Program 2 is the machine code created by the GENA 3 assembly program from Amsoft. From Program 2 you can create your object file which can then be loaded by Program 3. When loaded and run, these will ask for the Horizontal Resolution to be entered; this value determines not only the definition of the displayed picture, but also the proportion of the total picture width displayed across the screen. The first time a recording is run, select full width (4), and then any interesting parts may be re-run with a lower setting to obtain greater detail. The SHIFT switch may be used to move the picture to the desired position at the beginning of the run, and if required, the full scan may be re-started by holding the space bar. (The sync when set is not lost until the tape is stopped or the signal fails.) Synchronization to the start of a line is provided by the Sync Tone Card. The LINE SYNC switch selects the type of satellite and channel to be synchronized.
With the recording running and the appropriate position of the LINE SYNC switch set, synchronization is achieved by a short operation of the non-locking SYNC toggle switch.
The INPUT LEVEL control should be set to give an average reading of about half scale on the LEVEL meter. (Note that if a known peak white signal is being received, the level should be adjusted to give a full scale reading on the meter.) Advance the 'White Level' control until the peak white LED just starts to flash, then adjust the 'Black Level' until the black LED is just flashing. This setting should give a fairly good picture, but some experimentation with the settings of these controls is required to achieve the best results.
The LINES PER SECOND switch should be set to 2 lines per second for NOAA pictures, as channel A and channel B are sent alternately. The 4 lines per second position is used for satellites such as Meteosat when part lines are displayed to improve the aspect ratio and increase the vertical resolution.
The two preset positions of this switch are used for satellites with other line rates, and are programmed by using the diode cards. The Diode Card may either be fitted with DIL switches, or with diodes in a pre-selected matrix. When the DIL switches are fitted, cut the shorting tracks under the switches, and fit all diodes. The correct setting for a satellite is found by switching the LINES PER SECOND switch to the A position, inserting a diode card, with DIL switches installed, in position (nearest to the sync card) and trying different settings of the switches until a synchronized picture is obtained. Figure 14 shows some settings for Russian satellites that have been found to synchronize correctly. When the setting has been determined, the code may be 'copied' onto a blank diode card by inserting diodes only in positions that correspond to the positions of those diodes that connect to the switches that are in the ON position on the original (DIL switch) Diode Card. The shorting tracks are left intact. The connections to the SLIP switch also appear on the Diode Card, and these are made by inserting wire links below the diodes. The method of setting these links is as follows: Find the correct setting for the DIL switches as before, connect a short length of wire to the 'left' track and connect the other end to one of higher numbered pads marked X that does not have its associated switch in the ON (up) position. Run the tape and operate the SLIP switch to the LEFT position and note the effect on the picture. The correct setting is where the picture moves left at a controllable rate.
Once this connection point has been found, determine the position to the left of this connection where there is a switch in the ON position. Connect the RIGHT track to the 'X' connection of this position, and turn the switch OFF. Try running the recording again and check that when the SLIP switch is held in the RIGHT position, the picture moves to the right at a comfortable rate.
When the correct positions for the two connections have been found, perm anent wire links may be fitted.
The picture scanning may be stopped at any time by using the HOLD switch. (This does not lose synchronization if the incoming signal is uninterrupted.)
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DECODER DIODE BOARD--PARTS LIST
SEMICONDUCTORS
D1-12 1N4146
12 (QL8OB)
MISCELLANEOUS
S1,2 DIL
Switch SPST 6-Way 2 (FV44X)
Diode
PCB 1 (GD24B)
A complete kit of all parts is available for this project:
Order As LMO9K (Decoder Diode Board Kit)
Price £5.95
The following item in the above kit list is also available separately, but is not shown in the 1986 catalog:
Decoder
Diode
PCB
Order
As GD24B
Price £3.25
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Program 1.
Program 2.
Program 3.
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SATELLITE DECODER PARTS LIST
RESISTORS:
All 0.6W 1% Metal Film R1 27k 1 (M2TK) R2,4,25 470k 3 (M470K) R3,37,38,39,40 1k 5 (M1K) R5,9,20,27 10k 4 (M10K) R6,7,I2,24 100k 4 (M100K) R8 820f2 1 (M820R) R10 R11,17,26 R13 R14,41 R15 R16,21,22,23,28, 30,31,34,35,36 R18 R19 R29 R32,33 220k 2k2 160k 47k 6k6 4k7 180k 39011 33011 27011 1 3 1 2 1 10 1 1 2 (M220K) (M2K2) (M18OK) (M47K) (M5K6) (M4K7) (M180K) (M390R) (M330R) (M270R) SIL 1,2 SIL 4k7 2 (RA29G) RV1 10k Cermet 1 (WR42V) RV2 lk Hor. S -Min Preset 1 (WR55K) RV3 10k Pot Lin 1 (FWO2C) RV4 lk Pot Lin 1 (FWOOA) RV5 IM Pot Lin 1 (FWO8J)
CAPACITORS
C1-3 C4,5 C6,11 220nF Poly Layer 101/F 16V Minelect 47nF Poly Layer 3 2 2 (WW45Y) (YY34M) (WW37S) C7 100µF 25V P.C. Electrolytic 1 (FFI1M) C8,26,27 4µ7F 35V Minelect 3 (YY33L) C9 2/42F 63V Minelect (YY32K) CIO 2n2F Poly Layer 1 (WW24B) C12 4n7F Poly Layer 1 (WW26D) C13-18,28 100nF Minidisc (YR75S) C19-22 22004' 35V Axial Electrolytic 4 (FB90X) C23 10p.F 16V Tantalum 1 (WW68Y) C24,25 100nF Polyester 2 (BX76H) SEMICONDUCTORS D1,2 0A91 2 (QH72P) D3-14 1N4148 12 (QL80B) 2:0 I BZY88C3V3 1 (QH02C) LED 1 Red LED Chrome large 1 (YY60Q) LED 2 Green LED Chrome large (QY47B) TR1-3 BC548 3 (QB73Q) BR1 VV005 1 (QL37S) REG I pA7912UC 1 (WQ93B) REG2 pA7812UC 1 (41,32/C) REG3 pA7805UC 1 (QL31J) ICI LF353 1 (WQ31D IC2 ZN427E 1 (UF40T) IC3 NE565 1 (WQ56L) IC4 741.5132 1 (YF51F) ICS 4078 1 (QX28F) IC6-8 74HC163 3 (UB42V) IC9 74LS03 1 (YFO3D)
MISCELLANEOUS
M1 Signal Meter
T1 Transformer Toroidal 30VA 15V 1 1 (LB80B) (YK11M) S1 Switch Sub. Mm. Toggle SPDT (C)1 (FHO2C) S2,4 Switch Rotary 3-pole 4-way 2 (FF75S)
S3 Switch Sub -Min Toggle SPDT (D) 1 (FHO3D) S5 Switch Dual Rocker Neon (YR70M) FSI FUse IA A/S 1 (WR I9V) PL1,3 Minicon latch Pig 2 -Way 2 (RK65V) PL2 Minicon latch Plg 12 -Way (YW 14Q) PL4 Minicon latch Pig 6 -Way 1 (YW 12N) PL5,6 Minicon latch Plg 8 -Way 3 (YVV13P) PL7 R.A. 'D' Range 25 -Way PCB Pig 1 (FG68Y) SK1,3 Minicon latch Housing 2 -Way 2 (H1159P) SK2 Mincon latch Housing 12 -Way 1 (YW24B) SK4 Minicon latch Housing 6 -Way 1 (BH65V) SK5,6 Minicon latch Housing 8 -Way 3 (YW23A) Minicon Terminal 46 (YW25C) SK8 6 -Pin PCB DIN Socket 1 (FA90X) SK9 Power Socket D.C. 2.5mm 1 (FX06G) SK10-12 2x12 -Way P.C. Edgeconn 3 (BK74R) Polarising Key 0.156in 3 (FDO8J) Boh 6BA x lin 1 Pict (3F07H) 6BA x Viin Threaded Spacer 1 Pkt (FD1OL) Nut 6BA 1 Pkt (BF18U) Tag 2BA 1 Pkt (BF27E) Bolt 6BA x Vzin I Pkt (BFO6G) Mains Warning I-MPI 1 (WH48C) Cable Min Mains White 1 mtr (X1102C) Ribbon Cable 20 -Way 1 rat (XRO7H) Grommet Small 1 (FVV59P) S.R. Grommet 6W-1 (LR49D) Sleeving Heatshrink CP95 1 mtr (YR17T) Clip -on TO220 Heatsink 1 (FG62G) Decoder PCB 1 (GD22Y) Veropin 2141 1 Pkt (FI21X) DIL Socket B -pin 1 (BL ITT) DIL Socket 14 -pin 4 (BL18U) DIL Socket 16 -pin 3 (BL 19V) DIL Socket 18 -pin 1 (HQ76H) Safuseholder 20 1 (R)(96E) Knob KlOB 5 (RK90X) Transformer Mounting Bracket 1 (FDO9K) Constructor's Guide 1 ()(1179L)
OPTIONAL
Instrument Case NM2H 1 (YM51F) Decoder Front Panel 1 (FDO5F) Araldite 1 (FL44X) DIN Plug 6 -pin 2 (1-1H29G) Standard Power Plug 2.5 2 (HH62S) Cable Single Core Screened Greyl mtr (XR13P) Multi -Core 6 -Way 1 mtr (XR26D) Decoder Interface Cable 1 (FDITT)
A complete kit of all pans, excluding optional items, is available for this project:
Order
As LMOTH (MAPSAT Decoder Kit)
Price £79.95
The following items included in the above kit list are also available separately, but are not shown in the 1986 catalogue:
Sub-Min Toggle SPDT
Order As FH02C
Price £1.20
6-Pin PCB DIN Socket
Order As FA9OX
Price 50p
0.156in Edgeconn Polarizing Key Order As FDO8J Price 12p Vain x 6BA Threaded Spacer Order As FD1OL Price 88p Decoder PCB Order As GD22Y Price £12.95 MAPSAT Decoder Front Panel Order As FDO5F Price £3.95 Transformer Mounting Bracket Order As FDO9K Price £1.20 Instrument Case NM2H Order As YPII51F Price £14.95 Decoder Interface Cable Order As FD17T Price £6.85 Constructor's Guide Order As XHT9L Price 25p NV
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DECODER SYNC TONE BOARD--PARTS LIST
RESISTORS:
All 0.6W 1% Metal Film
R1 2k2 (M2K2) R2,10,11,13,22 47k S (M47K) R3 100k 1 (M100K) R4-7 33k 4 (M33K) R8,9 470k 2 (M470K) R12 68k 1 (M68K) R14 82k 1 (M82K) R15 18k 1 (M I 8K) R16,19 22011 2 (M220R) R17,18,20,21 R23 4k7 220k 4 1 (M4K7) (M220K) R24 RV1,2 RV3-5 CAPACITORS 2k7 47k Vert S. Preset 10k 23 -Turn Cermet 1 2 3 (M2K7) (WR70Q) (WR49D) C1,2,5,6 100nF
Poly Layer 4 (WW4IU) C3 2n2F Poly Layer 1 (WW24B) 16
Constructor's Guide
Order As XHT9L Price 25p NV C4 10nF Poly Layer 1 (WW29G) C7 100µF 16V Minelect 1 (RASSK) C8 10p.F 16V Minelect 1 (YY34M) C9,10 220nF Poly Layer 2 (WW45Y)
SEMICONDUCTORS
D1-3 1N4148 3 (QL80B) TRI-3 BC548 3 (QB73Q) IC1 4046BE 1 (QW32K) IC2 MF1OCN 1 (QY3SQ) MISCELLANEOUS Veropin 2145 1 Pkt (FL24B) Sync 1 PCB 1 (GD23A) Track pin 1 Pkt (FL82D) DIL seleket 20 -Pin 1 (HQ771)
A complete ldt of all parts is available for this project:
Order As LMO8J (Decoder Sync Tone Kit)
Price £12.95
The following item in the above kit list is also available separately, but is not shown in the 1986 catalog:
Sync 1 PCB Order As GD23A
Price £3.95
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