Through personal experiences with the PK-232, I have found that a somewhat
strange problem seems to have been isolated. I had recently had some difficulty
with the PTT not holding solidly on transmit. It seemed almost attributable to
the buffer/data flow into the unit, as the problem seemed to lessen in severity
when the threshold adjustment was increased so the unit could not transmit;
then by backing it off, it would send a packet stream without incident.
By accident almost, I finally decided to drop the input voltage to the tnc
(which had been fed by 14.5 volts – sharing a common power supply as the
transceiver). This immediately cleared the "chatter" problem. Apparently, the
232 uses the input voltage in a number of places, one of which is in the PTT
control circuit. Unlike the 5 volt stages, the 13 volt supply is NOT regulated
and thus whatever the input voltage is, that's what the "13+ volt" bus would

If anyone has similar problems with the PK232, it would seem that you have 3
  1. Buy an AEA or similar transformer to supply fixed 12.6 volts to the unit.
  2. Drop your power supply voltage to this point and sacrifice a little bit
     of power/performance from your transceiver
  3. Put in a separate 12 volt regulator circuit for the 232 separately.

I hope this has been of help for anyone who may have incurred similar diffi-

–Gary, WH6C

GW1NGL NA7KR Kevin Roberts Ham Radio

Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information