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Some commercial, weather and utility RTTY services send groups of<br />
numbers separated by spaces. When receiving such non-amateur signals,<br />
USOS should be OFF to prevent displaying LETTERS-shifted characters<br />
when the originator may have intended the data to be FIGURES-shifted.<br />
6.5.9 <strong>Operating</strong> at Commercial or VHF Wide RTTY Shifts<br />
Most commercial stations found in the non amateur Short Wave bands<br />
operate with a wide Frequency Shift keying of either 425 or 850 Hz<br />
shift. To allow these stations to be received the WIDESHFT command<br />
must be turned ON. If your license permits, you can also transmit to<br />
these stations when WIDESHFT is ON.<br />
6.5.10 The CODE Command for International RTTY Compatibility<br />
The CODE command allows the <strong>PK</strong>-<strong>232</strong> to receive (and sometimes send)<br />
other RTTY character sets. Part 97.69 of the FCC rules specifies that<br />
the International Telegraph Alphabet Number 2 (ITA #2) must be used by<br />
U.S. stations when operating RTTY. This corresponds to the CODE 0<br />
command (default), but you may want to see the CODE command for more<br />
information on what your <strong>PK</strong>-<strong>232</strong> is capable of.<br />
6.5.11 Copying Encoded RTTY Transmissions<br />
In the Short Wave bands many RTTY stations can be found that are not<br />
transmitting in plain text. Most of these stations are using<br />
sophisticated encryption techniques that make receiving them almost<br />
impossible. There are a few stations however that use a relatively<br />
simple bit-inversion technique to make them hard to copy. For these<br />
stations, the <strong>PK</strong>-<strong>232</strong> has included the BITINV command to allow the SWL<br />
to decode these simple forms of encoded RTTY stations.<br />
6.6 ASCII RTTY Operation<br />
ASCII RTTY operation is almost identical to Baudot operation but there<br />
are a few differences you must know. Because the ASCII code uses<br />
seven bits to define a character (instead of the five bits used in the<br />
Baudot/Murray code), the probability of receiving errors is somewhat<br />
higher. For these reasons, ASCII is not used widely on the HF amateur<br />
bands. However, some commercial and military HF stations do use ASCII.<br />
6.6.1 Starting ASCII Operation<br />
First you must enter the ASCII mode of the <strong>PK</strong>-<strong>232</strong>.<br />
If you are using an AEA PAKRATT program, follow the instructions in<br />
the program manual to enter the ASCII mode.<br />
If you are using a terminal, simply type "ASCII" or "AS" from the<br />
Command Mode followed by the key to enter the ASCII mode.<br />
The <strong>PK</strong>-<strong>232</strong> responds by displaying the previous mode:<br />
Opmode<br />
Opmode<br />
was BAudot<br />
now AScii<br />
Your <strong>PK</strong>-<strong>232</strong>'s front panel will show the CMD and ASCII LEDs lit.<br />
4/91 6-7<br />
From The <strong>N3UJJ</strong>.COM Document Library