Microlog SWL User manual

RADIO INTERFACE
CARTRIDGE FOR THE
COMMODORE ‘C-B4’
Complete terminal ith
soft are in permanent ROM
for Receiving RTTY and
MORSE Code.
MICROLOG
SWL
© MICROLOG CORPORATION 1986

INTRODUCTION
0.0 INTRODUCTION
Welcome to the world of digital communications. Your new
“SHORT-WA E-LISTENER” will turn your computer into a complete
listening post for those undecipherable coded signals you’ve heard.
Note, the cassette provided with the SWL is not a program — it is
to be played on a standard audio type recorder for demo purposes.
If you’re new to radioteletype and coded signals, the following in
formation will greatly aid in the enjoyment of your new receiving
capability.
0.1 As you know from listening on the short-wave bands, there is a
myriad of beeps, squeals and other mysterious sounding signals along
with normal voice broadcasts to be heard. A lot of these signals are not
MORSE or RTTY (RadioTeleTYpe), and are not copyable with the
“SWL.” Time code, fax, and navigation signals sound like RTTY, but
require specialized equipment designed to process that type of signal.
The good news is that the really interesting stuff is transmitted using
methods the “SWL” was designed to copy.
You’ve probably noticed that as you tune your radio in the
SSB/CW mode (or with the BFO on) the sound you hear varies in pitch
(frequency). The “SWL” detector circuits are listening for tones around
800 Hz (about 1 octave above middle C). By moving the tuning dial on
your radio, you can adjust the sound for exactly the right pitch. Simply
watch the on screen tuning indicators or use the pitch reference tone
heard through your video monitor’s audio channel. More on that in
Section 4 and 5.
Almost all forms of digital communications in use today involve
transmitting a binary pattern of “one’s” and “zero’s”, arranged in such
a way as to uniquely represent a number, letter or punctuation. The
simplest form of digital communications is of course, MORSE code.
Each character has its own pattern of long and short pulses, heard as a
dot or dash tone in the radio.
Radioteletype arranges the “one’s” and “zero’s” a little differently.
Instead of “tone/no-tone,” it uses two different tones (pitch). Tuning is
similar and just as easy. The trick is to tune the radio for the proper
pitch sound. As mentioned earlier, a lot of signals “sound” like radio
teletype but actually aren’t. If you just start tuning the shortwave
bands blind, you’ll probably be disappointed. Essentially, you have to
0-1

know where and when to tune and what to look for. Several good
publications are noted in Section 4 that show stations around the world
along with time and frequency. A few stations are also listed for you to
try. There are several parameters of a RTTY signal that must be known
in order to copy it. The information is sent using two tones. You must
know also:
1. The code or method of arranging the ‘T’s” and “0’s”
2. The speed or rate of information transmission
3. The shift, or separation between the tones
4. The sense, or which tone is the “1” and “0”
Although these look like a lot of variances, there are industry stan
dards for each parameter limiting the number of possibilities to only a
few. We’ll look at these individually.
0.1.1 Code
There is generally only one code in use on the shortwave bands;
the Baudot (pronounced “Baw Dough”) code. Occasionally you’ll find
some ASCII in the amateur radio bands, but even there, Baudot is most
prevalent. This is the code that the “SWL” will copy when first turned
on.
0.1.2 Speed
There are 5 standard speeds of Baudot (60-66-75-100 and 132
words per minute) only two of which are in common use. Amateur
operating is usually 60 wpm. Occasionally you’ll find a little 100 wpm.
Commercial RTTY is usually either 66 or 100 wpm.
0.1.3 Shift
There are three standard shifts or differences between the tones,
170, 425 and 850 Hz. Amateur operation is almost exclusively
“narrow” shift, 170 Hz (width switch on SWL in “narrow” position).
Commercial uses “wide” shift either 425 or 850 Hz, (switch in “wide”
position).
0.1.4 Sense
This parameter is described as being either “normal” or “inverted”
and refers to which tone is defined as the “0” or “1” of the code in use.
With your radio in the lower sideband, “normal” will put the tones in
the proper sense. If the transmitting station is listed as sending “in
verted” you can “invert” your copying logic by a simple keyboard com
mand. See Section 4 for more discussion.
0-2

0.2 RADIO FRE UENCY INTERFERENCE
Modern military computerized communications equipment is
housed in heavy metal enclosures. Mechanical durability is the primary
reason. A secondary but not so obvious reason is to keep radio frequency
energy from radiating from within or penetrating to the sensitive inter
nal circuits. With encrypted data, the main concern is radiation and
subsequent interception of the “clear” data from the box. Unfortunately,
home computer equipment must meet only minimal interference specs to
qualify for consumer sale. Simply put, home computers can generate
radio frequency signals from their circuitry that may be picked up on a
short-wave receiver. They’ll sound just like real radio signals and may
even have a buzzing “jammer” like quality. We have taken steps in the
design of the “SWL” to eliminate these “leakage” signals, but there are
certain conditions where you might have some interference. To verify
that it really is the computer making the noise, simply shut it off. If the
signal is still there, it’s not coming from the computer! Here’s a list of
some hints in setting up your listening post.
1. Don’t use the radio’s internal whip antenna or a short wire
(10-20') tied directly to the external antenna input. The close proximity
to the computer and relative inefficiency of the short antenna combine
to almost guarantee you’ll hear some computer noise. Use coaxial cable
(RG-58/U available at Radio Shack) to get the antenna out of the “near
field” of the computer. Make the antenna as long as is practical, 25' to
100' or more and orient it away from the computer/radio room. Use a
coaxial connector on the radio end and just snip the coaxial cable braid
(outer shield wires) up at the antenna feed point. Connect the center
conductor only to the antenna wire. Use of a “dipole” type antenna is
also quite acceptable.
2. Don’t use “amplified” antennas, short whips with integral high
gain pre-amps for the same reasons as above, unless the actual antenna
is at least 50' from the radio/computer.
3. It’s always helpful to provide a good ground for the radio. This
may well be accomplished by a 3-wire grounded line cord. If the radio
is battery operated, or uses a 2-wire ac line cord, you should run a
separate chassis ground wire to a cold water pipe or outside ground
rod.4. Sometimes physically changing the position of the radio, com
puter and video monitor can signficantly alter extraneous pick-up.
0-3

CHAPTER 1
‘SWL’ PRELIMINARY CHECKOUT
After unpacking your unit, make sure that power to the computer
is turned off, then plug the ‘SHORTWA E LISTENER’ cartridge into
the “expansion port” (The same one used for game and memory expan
sion modules), so that the label is on top, facing up. Turn on the com
puter and video monitor. The word “MICROLOG” will appear on the
screen for several seconds then the following “TOPLINE” display
should appear on the video screen.
R B 0 6 0 W PM NOR U 0 0 : 0 0 UTC
This indicates that the system is set to receive (R) Radio teletype,
using Baudot (B) code at 60 WPM, and that the built-in dual tone
demodulator is selected in the Normal (NOR) mode, with the “UN
SHIFT on SPACE” feature enabled (U). A four digit HH:MM clock
which should start advancing is displayed with flashing colon. UTC is
the time zone displayed until you change it.
The “Split Screen” cursor will be displayed in the left center of the
screen in white. The receive text cursor will be at the bottom left screen
in yellow. If using a monochrome (black and white) T /monitor, colors
will appear as shades of gray.
In the event that the above does not appear on your video
monitor’s screen, check the cable between the computer and the T
monitor to make sure that it is not shorted or open. You may also have
to adjust the T monitor’s various controls such as brightness, contrast,
etc. Some monitors provide a switch which selects a low or high im-
pedence input. You should select the low impedence (75 OHM) input.
Also, if your monitor has a “PICTURE-DATA” switch it should be in
the “DATA” position. Connections to a standard television are exactly
the same as when using the computer.
DEMO TAPE NOTES
A standard audio cassette is included with your “SWL” cartridge.
It is not a program — do not try to “load” this tape. It is a demo of the
SWL’s receiving capability and should be played on a normal audio
cassette player. Connect the earphone or external speaker output of the
1-1

recorder to the SWL’s “speaker/earphone” jack. Start the tape,
gradually increasing the volume until the SWL starts to copy the text
from the tape and display at the bottom of the video screen. Don’t turn
the volume up too high because it will overdrive the SWL’s tone detector
circuits and make mistakes in the copy. Make sure the nar. wide switch
on the SWL is in the wide position.
1-2

CHAPTER 2
‘SWL* SYSTEM
FAMILIARIZATION
2.1 KEYBOARD:
Your “64” keyboard has a total of 67 keys including all of the
familiar Alpha-Numeric keys. In addition there are special symbol
keys, and two keys, namely ‘SHIFT’ and ‘CTRL’ which are always us
ed in conjunction with another key. The SHIFT key(s) are located on
the bottom row and the CTRL key is located on the left side above the
RUN/STOP key.
Note that some of the key tops have two symbols. For example, the
4 and the $ symbols are engraved on the same key top. Much the same
as in a standard typewriter you must hold the SHIFT key down while
pressing the 4 key in order to type the $ symbol. The CTRL key is used
in a similar manner.
In the following description, references are made to various con
trol functions or commands. These commands are executed by
simultaneously pressing the CTRL (or SHIFT) key plus one other key.
For example, a request to press (or type) ‘CTRL X’ means that you
must hold down the CTRL key, and while holding it down, press the X
key, then release both keys. Similarly, to type or press ‘SHIFT X’ means
that you should hold down the SHIFT key, and while holding it press
X. As soon as the X key has been pressed you can release both keys.
After familiarizing yourself with the location of the various sym
bols on the keyboard, type some Alpha-Numeric text. Observe that the
characters you have typed are displayed on the upper part of the screen
above the split-line. The ‘INST/DEL’ key which is located on the right
side of the top row may be used to correct typing errors. Notice that
typing ‘INST/DEL’ erases the previously typed character.
You can go to the “BASIC” computer mode by typing ‘CTRL’ and
Commodore keys. Since you are then under the restraints of “BASIC”
language, to go back to SWL communication mode you must type: SYS
32777 then the ‘RETURN’ key (64 Basic memory shows 30719 bytes
free with ‘SWL’ installed. Some programs that need the full 38911
bytes of memory will require that you unplug the ‘SWL’. Be sure to
disconnect the cable to your radio first and always turn off the com
puter before unplugging the ‘SWL’.)
2-1

2.2 IDEO DISPLAY COMMANDS:
The split-screen option is user selectable. The ‘CTRL S’ command is
used to toggle the split-screen screen on and off. To remove the split
screen and use the entire video display for receive text,
TYPE: ‘CTRL S’ (HOLD ‘CTRL’ KEY AND PRESS ‘S’)
2.2.1 COLOR CHANGES:
The screen and text colors can be changed with a single control
command. “CTRL G” followed by a 4 digit number will change the
following:
screen background color
receive/data
textmode display
top line status display
The f s are the same as the 64’s color codes as shown on page 139 of the
64 manual with one exception. To utilize a single digit for all 16 colors,
you must enter it in “Hexadecimal” that is 0 through F instead of 0
through 15. The colors are as follows:
0 = Black
1 = White
2 = Red
3 = Cyan
4 = Purple
5 = Green
6 = Blue
7 = Yellow
8 = Orange
9 = Brown
A = Light Red
B = Dark Gray
C = Med Gray
D = Light Green
E = Light Blue
F = Light Gray
The colors will change upon typing the forth digit. Note: The default
colors are:
(6) Blue Top line
(1) White Text buffer
(7) Yellow Receive data
(E) Light Blue Screen
These colors were picked as the best compromise for both color and
monochrome display. You can experiment with different color patterns
to suit your individual requirements. Suggestions: 0657, 1AE0, 192A,
569D, 062C.
2-2

Note also, the tuning indicators and the RX buffer flags are always
displayed in red.
You can move the entire video display horizontally with the CTRL
H command. This should take care of monitors with limited horizontal
sync tracking range.
2.3 TEXT/RCV COMMANDS:
The text mode is useful for inserting your own notes in the printed
copy off the air and for familiarizing yourself with the sound of the
various codes. It also makes a great “letter writer” too, if you have a
printer connected.
Typing ‘SHIFT RUN/STOP’ or ‘SHIFT RETURN’ (hold ‘SHIFT’,
press ‘RUN/STOP’) places the system in the text mode. Observe that the
top line display has changed and is now displaying:
T B 060WPM NOR CHAR
indicating that the system is now in the Text Mode (T), and that each
character will be sent as it is being typed (CHARacter mode). Type some
Alpha-Numeric text and observe that the typed text is displayed above
the split-line and also below the split line. The text which is displayed
below the split-line represents the actual text as it is sent. The text which
is displayed above the line represents the entries into the system’s text
buffer.
Return the system to the receive mode with the RUN/STOP key by
itself or by typing ‘CTRL CLR/HOME’ (hold the ‘CTRL’ key and press
the key labled ‘CLR/HOME’). Observe that the top line display has
changed indicating that the system is in the Receive mode. Type in some
text and note that it is no longer displayed below the split line.
2.4 SPEED SELECTION COMMANDS:
NOTE: the right hand bracket ] is the symbol for a terminated com
mand sequence which required further keyboard input such as speed
select or memory store. When you first initiate these commands, you
should not see anything on the screen. If you see the ‘ ] ’ it means that
particular command has been terminated. Hitting ‘CTRL X’ twice for
example will only terminate the command without it taking affect.
The operating speed (RTTY and MORSE) is selected by means of
the ‘CTRL X’ command. The allowable RTTY BAUDOT speeds are
60, 66, 75, 100, and 132 WPM. ASCII code speeds are 110 and 300
baud. For MORSE, speeds from 5 to 99 WPM are permitted. To select
an RTTY (BAUDOT) speed of 66 WPM (SAME AS 50 BAUD), first
type ‘CTRL B’ if not in BAUDOT already, then:
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TYPE: ‘CTRL X’ (SPEED SELECT COMMAND
NOTHING SHOWS ON THE
SCREEN)
TYPE: 66 (DESIRED SPEED)
TYPE: ‘CLR/HOME’ (OR ANY NON-NUMERIC KEY
PRINTS ])
Observe that the top line displays
R B 066WPM NOR
To select an RTTY (BAUDOT) speed of 100 WPM (same as 75 baud),
TYPE
TYPE
TYPE ‘CTRL X’
100
‘CLR/HOME’
Observe the speed display on the top line is now 100 WPM.
To select an RTTY (ASCII) rate of 110 baud,
TYPE: ‘CTRL A’
System will automatically go to 110 BAUD when ASCII is selected.
Observe that the top line displays A-110 BD (BAUD) where the ‘A’ in
dicates that the selected code is ASCII.
To select an RTTY (ASCII) rate of 300 baud, (no need to type ‘CTRL A’
since you are already in ASCII)
TYPE
TYPE
TYPE ‘CTRL X’
300
‘CLR/HOME’
Note, if you are in 300 BAUD ASCII, to change to any other speed or
code, you must first go to 110 BAUD ASCII. The jump from 300 BAUD
ASCII to MORSE or BAUDOT directely is not allowed.
Go back to RTTY (BAUDOT) speed of 60 WPM (Same as 45 baud),
TYPE
TYPE
TYPE
TYPE
‘CTRL B’
‘CTRL X’
60
‘CLR/HOME’
(ASCII stands for American Standard Code for Information Inter-
2-4

change, whereas ‘BAUDOT’, pronounced ‘BAW DOUGH’ is a man’s
name.)
NOTE, you can omit the ‘CLR/HOME’ key if you enter the speed with
three digits, 110, 066, 075 etc., since the program automatically ter
minates the command on the third digit.
2.5 MORSE/TTY SELECT COMMANDS:
Enter the MORSE mode by typing ‘CTRL M’ (hold ‘CTRL’, press
M) and the top display line should read:
R M 020WPM NOR
indicating MORSE (CW) mode with speed set for 20 wpm. The system
will remember the previous MORSE and RTTY speed when changing
to and from modes. Go to the text mode by typing ‘SHIFT RUN/STOP’
and observe that the display has changed and the letter‘T’ has replaced
the ‘R’ on the left top display line. Turn up your audio channel volume,
and type in some letters and numbers. You will hear the MORSE code
as it is displayed below the split-line. To change the speed use the
‘CTRL X’ command. Also, when the text buffer is empty, if desired,
the MORSE equivalent of a “diddle”, BT, can be sent. Type ‘CTRL D’
to toggle the “diddle” mode on/off. To select a MORSE speed of 17
words per minute,
TYPE: ‘CTRL X’
TYPE: 17 (NEW SPEED)
TYPE: ‘CLR/HOME’ (OR ANY NON-NUMERIC KEY)
Observe that the newly entered MORSE speed is now displayed on
the top line. Any MORSE speed from 5 to 99 WPM may be selected.
NOTE: In the receive mode, the displayed MORSE speed will
usually be within plus or minus one digit of the speed you set since this
is an “averaging” parameter. As you receive some MORSE characters,
the receive speed readout will track the incoming speed, (assuming
speedlock is not enabled) but will not change the selected text mode
transmit speed.
Return the system to BAUDOT TTY mode by typing ‘CTRL B’.
The top line should display,
R B 060WPM NOR
2-5

2.6 CLOCK COMMANDS:
The SWL includes a real time clock with a 4 digit display of hours
and minutes, and a 3 character time zone. When the unit is first turned
on the clock is reset to 00:00. You can set the clock to start at any time
by means of the ‘CTRL K’ command. For example, initialize the clock
to start at 1758GMT,
TYPE: ‘CTRL K’ (CLOCK SET COMMAND—CLOCK
DISPLAY WILL FREEZE)
TYPE: 1758GMT (DESIRED TIME AND ZONE)
TYPE: ‘CLR/HOME’ (THIS STARTS THE CLOCK)
The clock will be restarted at 1758GMT as soon as you hit the
‘CLR/HOME’ key (or any non-numeric key) and the video line will
display: 17:58 GMT
The clock obtains its timing reference from the CPU Crystal fre
quency and should maintain good accuracy. The clock will have to be
reset if power is lost.
The system’s clock time can be inserted in the text buffer by means
of the ‘CTRL C’ command. Type ‘CTRL C’ and observe that the clock
time is displayed on the lower half of the screen if you are in the text
mode. If you turn up the monitor volume, you can hear the code being
sent.
2.7 MEMORY STORE/RETRIEVE COMMANDS:
The SWL includes a number of user programmable memories.
These are useful for storing phrases and comments that are used often.
There are 8 message memories of 512 characters each, 2 ID memories of
64 characters each and 2 Selective print memories of 11 characters each.
You can store messages at any time, even during a text print.
You can store your name or date into the ID memory by means of
the ‘CTRL £’ command. For example, to store the date, 19 Oct 85,
TYPE: ‘CTRL £’ (‘HOLD CTRL’ AND PRESS *£’ KEY
NOTHING SHOWS ON SCREEN)
TYPE: ‘SPACEBAR’ (PUTS A WORD SPACE)
TYPE: 19 OCT 84
TYPE: ‘CLR/HOME’ (EXITS MESSAGE STORE MODE
PRINTS ])
As you type the date in, it will be displayed above the split-line.
You can correct typing errors by means of the ‘INST/DEL’ key. To
2-6

retrieve and send the stored date simply press the £ ’ key. The date
previously stored will be inserted into the text buffer for transmission
and displayed above the split-line.
You can store a second short phrase or call sign by using the CTRL
I command. For example, to store the call sign K3ICH/4,
TYPE: ‘CTRL F
TYPE: ‘SPACEBAR’
TYPE: K3ICH/4
TYPE: ‘CLR/HOME’
This memory will be set by pressing ‘SHIFT £’ with a “space”
preceding it.
To store a message into any one of the 8 available message
memories you must first type ‘CTRL’, and memory number (1 to 8),
then enter the message text, and terminate by typing ‘CLR/HOME’.
For example, to enter: “RECEI ER — DRAKE R7” into memory
number 1,
TYPE: ‘CTRL l’(HOLD ‘CTRL’, PRESS ‘l’)(NO DISPLAY)
TYPE: RECEI ER — DRAKE R7 (TEXT DISPLAYS)
TYPE: ‘CLR/HOME’ (SHOWS “]’ ON SCREEN)
To send this stored message, simply press and release the ‘F-l’ key
(right hand function keys). In a similar fashion you can store and
retrieve messages from the other 7 memories.
If your message is longer than the selected number of characters it
will simply overflow into the next message memory location. For exam
ple, if you store a message that overflows into memory 2, it will be pro
perly retrieved in its entirety by typing ‘FI’. If you type ‘F2’, you will
retrieve the last remaining characters of the message, which over
flowed into ‘F2’.
You must use the ‘CLR/HOME’ key, or any ‘CTRL’ key to ter
minate and exit the message store mode. If you do not, you will con
tinue to store characters until you have filled the entire message buffer.
Normally, each of the user programmable memories in the SWL is
512 characters, which leaves about 28,000 characters for the text buf
fer. By typing CTRL ‘< >’ (up/down cursor) you can create a receive
buffer of 14,000 characters. Typing the same key ‘< >’ by itself will
send this new memory.
You can also recall and send two permanently programmed
messages. Pressing ‘CTRL’ followed by the “Q” key, will recall the
2-7

“QUICK BROWN FOX ...” message, and following the “CTRL” by
the “R” key, will recall the “RYRYRY ...” message.
The two selective print memories can store up to 11 characters
each. These are entered exactly as for the first 8 memories except that
you access these memories by typing ‘CTRL 9’ and ‘CTRL 0 ’ respect
ively.
When the system ‘hears’ the specific string stored into the “9”
memory, the printer port will be enabled, and when it ‘hears’ the string
corresponding to the one stored in “0 ” memory, the printer port will
j be disabled. Manually typing ‘CTRL P’ or ‘CTRL ’ also
enables/disables the printer port. See Chapter 6 for more info.
t To display the current contents of these memories press ‘CTRL>’
(period key). The contents of the “9” memory are shown next to PON:
(printer on), and the contents of the “0 ” memory are shown next to
POFF: (printer off).
The “ = ” memory contains the WRU (Who aRe yoU)
KEYWORD, shown next to WRU. This function is only used in the
transmit/receive version of this program.
See Section 7.2. for information on creating ‘OFF-THE-AIR’
Receive Memory.
2.8 TEXT MODE COMMANDS:
The program has a number of transmission modes. In the
CHARacter mode (this is the system default mode), each character is
sent as it is typed. In the WORD mode, an entire string of characters is
transmitted as soon as the spacebar key is pressed. In the LINE mode
the typed characters are transmitted as soon as the ‘RETURN’ key is
pressed. The WORD and LINE mode are only used in the transmit ver
sion of this program.
2.9 TEXT EDITING COMMANDS:
The SPLIT-SCREEN option lets you see what you type, and
allows you to correct typing errors before they are sent to the printer. If
you are in the text mode, you can enable the WORD or LINE mode as
explained above.
You can correct typing mistakes by pressing the ‘INST/DEL’ key.
Pressing this key will cause the previously entered character to be
erased and you can correct it. Each press of the ‘INST DEL’ key will
erase one character.
2-8

The entire text buffer may be cleared at any time by typing ‘CTRL
CLR /HOME’. This will also clear the screen and place the system in
the receive mode.
You can repeat a segment of text by means of the ‘—’ key. To
repeat the printing of a text segment first type ‘SHIFT — ’ (press the
‘SHIFT’ and ‘ —’ keys). This serves to point to the beginning of your
text. Now enter your text, which will be printing if you are in the text
mode. Press the ‘ —’ key and the text will be repeated. Press it again and
it will be repeated for the third time.
I
i
2-9

CHAPTER 3
‘SWL’ RADIO
CONNECTIONS
The SWL provides all of the interfaces required for direct hookup
to your receiver. For the following description refer to the rear connec
tion diagram below.
3.0 AUDIO INPUT:
Audio from your receiver is connected to the SPKR/EARPHONE
AUDIO jack on the SWL. Connect the shielded cable provided be
tween the EARPHONE or external speaker output of your receiver and
the SPKR EARPHONE input on the SWL. You will note that there are
two “SPKR EARPHONE” phono jacks on the SWL. These are con
nected internally on the board. This allows you to plug one cable from
your radio to the SWL, and one cable out to your external speaker or
headphone, eliminating the need for a “Y” connector. Refer to the
diagram showing the SWL rear connections.
CONNECT TO EITHER
EXTERNAL SPEAKER OR
EARPHONE OUTPUT OF
YOUR SHORT WAVE RADIO
3-1

CHAPTER 4
‘SWL’ RTTY OPERATION
The SWL contains a dual tone demodulator designed to receive
both amateur and commercial RTTY signals. The center frequency is
around 800 Hz which is compatible with all shortwave receivers in
common use.
The “WIDE-NARROW” switch selects between 170HZ “NAR
ROW” shift, and 425/850HZ “WIDE” shift.
At the present time the 170HZ shift is in almost exclusive use by
amateur RTTY operators. Whereas most commercial stations use wide
(425 or 850 Hz) SHIFT.
Selection of inverted RTTY reception is accomplished by means of
the ‘CTRL (minus) command. ‘CTRL + ’ (plus) selects normal
(noninverted) RTTY operation. The selected mode is always displayed
on the top video line as NOR or IN .
4.1 AMATEUR OPERATION:
Place your receiver in the lower sideband mode, or adjust your
BFO for lower sideband and tune in an amateur RTTY signal. A good
band to try is the 20 meter amateur band between 14080 and 14100
KHz. Try to locate a relatively strong RTTY signal, and listen to the
received audio. Your receiver should be tuned so as to produce tones
around 700 - 900 Hz.
When the signal is properly tuned, the on screen tuning indicator
will flash in synchronism with the incoming audio tones. The cross
hatch tuning aid simulates the pattern observed when using an
oscilloscope for tuning. Proper tuning is indicated when a cross is
displayed. The Mark displays a horizontal bar and Space displays a
vertical bar. You will also note that when properly tuned, the red dot
“signal acquisition indicator” is on constantly. If this dot blinks out, it
either means the signal is not tuned properly or the audio volume is not
high enough. As a further aid in tuning, the computer tone synthesizer is
used to generate an 800HZ switched reference tone. This tone is
available on your television (monitor’s) audio channel through the
speaker just as various sound effects are heard when using game pro
grams. Simply turn up the volume on the T to hear the tone. The tone
should sound clean and should be synchronized with the tuning in
dicator, such that it is “on” during “Mark” (horiz. bar) reception.
4-1

Set the system to 60 WPM RTTY operation as this is currently the
most popular speed used by amateurs. The mode and operating speed
are permanently displayed on the top line of your video screen. To
change the operating speed use the ‘CTRL X’ command to set it
directly.
If you are properly tuned, the tuning indicator will alternate be
tween a vertical and horizontal bar at the received bit rate which ap
pears as a cross. If you turn on the reference tone, it should sound clean
and be in sync with the received audio.
4.1.1 SELECTABLE OPTIONS:
RTTY reception is further enhanced by means of a number of
keyboard selectable options. For a full description of the available
RTTY commands see Chapter 7.
You can eliminate the display of most non RTTY signals such as
voice or CW by enabling the ANCW (ANTI-CW) option. This option is
commanded ON/OFF by means of ‘CTRL T’ command. When enabled,
this ANCW option will inhibit the display of voice and most CW
signals. It will also inhibit the display of inverted RTTY signals. There
will, however, be a slight delay when you first tune a new RTTY signal
before the display is presented on the screen. The letters ‘ANCW’ will
appear on the top line display when in RTTY receive mode.
The actual software (program) operation of the ‘ANCW’ is to in
hibit the video display until 10 properly timed stop bits are received in
a row. If two stop bits are missed, the “10” counter is reset and the
display is disabled until 10 more stop bits are received in order.
The mechanical teleprinter keyboards that use the Baudot code
have fewer keys than a standard typewriter. There are no “lower case”
letters in Baudot, only “upper case” caps. Actually the figures and
punctuation symbols are the shifted upper case with caps letters as the
lower case characters. Hence the terms LTR (letter) and FIG (figure)
shifts. The Unshift On Space function when enabled, will cause an
automatic shift to the LTR (lower case) mode upon the receipt of a
BAUDOT word space code. This option is useful in that it will not get
the system “hung-up” in the FIG (upper case) mode in the event of a
failure to detect a BAUDOT LTR (down shift) code. This option is
enabled and disabled by means of the ‘CTRL U’ toggle action com
mand. When receiving Weather Reports, turn the ‘UNSHIFT’ option
off, as they do not send a FIG shift after each group of numbers. When
not in “UNSHIFT” mode, the SWL will simply react like a mechanical
teleprinter. When enabled, the letter ‘U’ will appear near the right side
of the top line. It is initially on at power up, and not displayed during
text printing.
4-2

The reception of a CR (carriage return) code causes the display to
start a new line. The system may be inhibited from starting a new line
when the CR code is received. The CTRL F command is used to enable
and disable the start of a new display line when the CR code is received.
Many printers automatically insert a line feed after receiving a
carriage return. By utilizing the CTRL F command, double spacing
can be eliminated on these printers.
4.2 COMMERCIAL RTTY:
Your SWL can be used to copy many commercial RTTY stations
transmitting news bulletins and weather data. While the use of a
general coverage receiver is most useful, you will find some signals just
above the amateur HF bands, in the event you have a HAM-BAND
only receiver.
Most of these transmissions will be at 66 WPM (50 baud) with a
few, especially weather stations, at 100 WPM (75 baud). These speeds
are available to you by means of the ‘CTRL X’.
You may also encounter some stations which are utilizing a non
Latin alphabet, such as Russian, Arabic, etc. You will of course not be
able to decode such transmissions. You should however find numerous
stations using the standard Latin character set with transmissions in
various languages including English.
Commercial stations in general use a wider shift, with 425HZ as
the most typical. Your “NARROW-WIDE” switch should be in the
“WIDE” position.
Note that WEATHER bulletins appear in a fixed format. The start
of a bulletin is indicated by the 4 letter group ZCZC, and its end by the
letter group NNNN. The actual weather information consists mostly of
a number of 5 figure groups, interspaced with plain English and ab
breviations.
When receiving a Weather bulletin, turn off the unshift on space
option in order that you do not shift to letter mode when they send a
word space code. If the “UNSHIFT” is on, you will print letter groups
instead of figures. You can toggle the “UNSHIFT” option on/off by
means of the ‘CTRL U’ command. If you miss a “FIG” code, you can
force the unit to “FIGS” by typing “CTRL Y.” This has the same effect
as if you received the “FIG” code.
4-3