Date: Fri Apr 06, 1990 11:31 pm EST From: 31002_1650 EMS: INTERNET / MCI ID: 376-5414 MBX: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!watserv1 MBX: !ria!uwovax!31002_1650 MBX: @tut.cis.ohio-state.edu TO: * Scott Loftesness / MCI ID: 380-1143 TO: packet radio EMS: INTERNET / MCI ID: 376-5414 MBX: packet-radio@ucsd.edu Subject: The following is a relatively easy modification that allows reliable 19.2 K baud on the serial port and radio port of most TAPR TNC-2 boxes. ***** FIRST AND FOREMOST ***** Replace U3 (LM324 op amp) with a TL084CN or TL094 if no TL084CN or eqiv. This is a high speed JFET hi-Z op amp. Just that fix alone will allow you to run 9600 baud on the serial port to your computer. I found that the TAPR 1.1.6. code WITH the PMS ran without any serial port misbehaving BUT it was sluggish. The 1.1.6. code (or lower) without PMS is quite a bit quicker. ***** 19.2 K ***** Cut the PC trace that goes to pin 2 of divider U1 about 1/8" from U1. Run a short jumper from pin 10 of the divider U1 to the side of the trace you just cut that goes to the SW2 baud rate switch. This is the side of the cut opposite to pin 2 on U1. This supplies a 307.2 K clock to pin 1 and pin 6 of the SW2 which NO LONGER SELECTS 300 BAUD. The 307.2 K is 19.2K/16 which is fine and dandy. To run 19.2K on the serial port, turn SW2 switch 1 on. SW2 switch 6 selects 19.2 K to the MODEM port, switch 7 selects 1200 baud to the modem port and switch 8 selects 9600 baud to the modem port. ( keep in mind to leave switch 7 on unless you have installed a higher speed modem in your TNC ) We are running 19.2 K serial and 9600 baud radio with G3RUH modems and kantronics DVR 2-2 radios with excellent results. Next step is to up the G3RUH boards to 19.2 K by replacing a couple of capacitors. OHHH WHAT A FEELING....... de Anthony Varga VE3ZAV Kellogg Canada Inc London, Ontario, Canada 519 455 9660 Vmx 367 519 681 1650 Home