PK-232 MBX – OPERATING MANUAL PACTOR OPERATION
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11.11 Pactor Switching-Time Considerations
For operation in Pactor ARQ, your transceiver or transmitter-receiver combination must be
able to change between transmit and receive within 130 milliseconds. Most modern solid
state radios can easily meet this specification. Many older tube-type radios that use electro-
mechanical relays also operate very well in Pactor ARQ.
If the changeover from transmit to receive is too long, the minimum working distance is ex-
tended; the signal to the distant station will arrive before the station has switched back to
receive. However, if the transmitting station is further away, the transmission time over the
propagation path will delay the arrival of the signal until after the station has switched to re-
ceive. For this reason, you may be able to 'Link with' stations across the country, but not
across town.
If the receiving station's changeover from transmit to receive is too slow, the transmitting
station delay between "PTT" and "data send" can be extended. See the ADELAY command
in the Command Summary to adjust the PK-232's Pactor timing characteristics to compen-
sate for this.
11.11.1 Suggested Pactor operating Settings
If you have trouble synchronizing with another Pactor ARQ station, try some of the follow-
ing operating tips before calling Timewave or deciding that your radio equipment needs
modifications:
o Try to work the distant station on the unproto mode to establish that the other sta-
tion's system is fully functional.
o Don't use VOX control – use the PTT line from your interface.
o Turn off the AGC circuit – use the RF gain control to prevent receiver blocking on
stronger signals.
o Turn off all compression or other audio processing.
o Keep the AFSK audio input level to the microphone circuit as low as possible – avoid
over-driving the audio input stages.
o Disable the ALC circuit or reduce excessive ALC action; use more effective RF anten-
na loading to adjust output power levels.
11.11.2 Possible Areas for Pactor Performance Improvement
If switching-time problems persist, you may have to make changes in the radio to elimi-
nate excessive time delays:
o Remove large decoupling capacitors from the Push-To-Talk line to allow faster PTT
(transmitter) activation;
o Improve power supply decoupling, especially in audio stages.
o Do not use the squelch control.
In case you can't solve your radio’s switching-time problems, please call Timewave's Cus-
tomer Service Department (see the front of this manual).
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