Hal Communications CWR6850, Instruction Manual

Page: 31 / 64

CHAPTER 4 PAGE 31
FREQUENCY RANGE MAXIMUM DATA RATE EMISSION
3.5 to 21.25 MHz
28.0 to 225 MHz
420 MHz and higher 300 baud
1200 baud
19,600 baud
F1
F1, F2, A2
F1, F2, A2
Although there are many data rates available for use, 110 baud is used almost exclusively on fre-
quencies below 30 MHz due to popular use, commercially available mechanical machines, and the
poor noise performance of higher data rates. On the VHF bands, 110, and 300 baud have proven
popular. The internal demodulators of the CWR6850 will not provide optimum signal performance if
300 baud is used; the low-pass filter is set for a narrow bandwidth to give optimum performance
at the more common, slower data rates. Use an external modem for 300 baud, such as a "BELL
103 - Compatible" modem.
However, there is a big advantage to use of the slower data rates (45 or 50 baud for example)
with the ASCII code in the 3–30 MHz frequency range. The slower data rates are considerably
more effective when faced with the noise, interference, and varying signal conditions common on
these frequency bands. Also, the ASCII code offers a considerably larger character set than the
Baudot code normally used at these slow rates.
The CWR6850 will transmit and receive a full ASCII character set, including upper and lower case
letters, all punctuation and symbols, and all control codes with the exception of the "US" (Unit
Separator) code (001 1111). Each ASCII character and control code has a unique symbol that is
displayed on the CWR6850 screen. These symbols are shown in Table 3. The key combinations
used to produce the ASCII control codes are also shown in Table 3. Note that it is necessary to
press the "ESC" key before typing the "CTRL-
n " combination since many of the "CTRL- n " keys are
used for CWR6850 control. A complete listing of the ASCII codes is shown in Table 4.
Often, it is desirable to be able to transmit an abridged form of the ASCII code, using only upper
case (capital) letters. This feature, called CAPS LK, is turned on with the LOCK / UOS ON switch. In
ASCII, this switch selects CAP LK when it is depressed. This feature effects both the transmit and
receive sections of the CWR6850 - only upper case ASCII characters may be received and trans-
mitted when the LOCK switch button is in.