PK-88 OPERATING MANUAL
INSTALLATION
2 - 10
PK-88 - 26
o
Set VOX to OFF.
o
Set speech compression to OFF.
o
Set AGC to FAST (if available).
o
Disconnect the ALC cables between your SSB radio and any external RF amplifier
you wish to use in Packet-Radio service.
NOTE:
Make all connections with power off.
If your radio has a phone patch input and external PTT connections, the PK-88 AFSK out-
put can be connected to those input jacks, leaving the microphone jack for normal serv-
ice. However, some microphones are connected at all times (regardless of the PTT line's
state. In this case, disconnect the microphone to prevent inadvertent loading of the audio
input circuit. If the phone patch jack has a series isolating resistor, your microphone can
remain connected.
1.
Connect the PK-88 and SSB radio as shown in Figure 2-1.
2.
Apply power to the PK-88 and your computer and start the terminal program.
3.
Connect your SSB radio to a dummy load.
4.
If your SSB radio has a 'monitor' facility, i.e., an audio output that lets you listen to
the audio signals entering the microphone or phone patch jacks, turn that monitor
circuit on.
5.
Set the radio MODE selector to either USB (upper sideband) or LSB (lower side-
band). Because Packet-Radio uses NRZI data on the radio link, the sideband used
does not affect the data sense or polarity. However, the radio's tuning calibration or
frequency display will vary depending on which sideband is selected.
6.
Set the radio's meter switch to the 'ALC' position. If the radio doesn't have an 'ALC'
indication, set the meter switch to 'IP' to read output device or plate current. If an
output device or plate current reading isn't available, set the meter to indicate
power output.
7.
Set the PK-88's TONE value to either TONE 0 for the low tone pair or TONE 1 for the
high tone pair.
8.
Set
HBAUD
to
300
.
9.
Enter the Calibrate mode by typing
CAL [RETURN]
.
Ignore the 'zeros' scrolling down the left side of your screen. The self-contained
7910 modem chip does not require calibration or tone adjustments. The 'zeros' ap-
pear only to show that the PK-88 is in the 'Calibrate' mode for the purpose of keying
the transmitter and applying steady-state tone modulation for transmitter adjust-
ment.
NOTE:
In the Calibrate mode only the 'K' key toggles the transmitter PTT line on
and off. The 'SPACE BAR' toggles the PK-88's AFSK tone generator from
'Mark' (Stop Polarity, the lower-pitched tone) to 'Space' (Start Polarity, the
higher-pitched tone). The PK-88's transmit watchdog timer circuit unkeys
