*******************************************************************************
                  Commoning TNCs when using BPQ software
*******************************************************************************

       25 WAY FEMALE TO PC

########     2  3  7   ############
2------------|  |  |
             |  |  |
3---->|------+--|  |
             |  |  |
20--c  e--|  |  |  |       TNC1
     b    |  |  |  |       WITH
     |    |  |  |  |      THENET
     r    |  |  |  |        ROM
5----+-|<-|  |  |  |     INSTALLED
          |  |  |  |
7---------+--+--+--|
########  |  |  |  |   ############
          |  |  |  |
2---------+--|  |  |
          |  |  |  |
3---->|---+--+--|  |      TNC2
          |  |  |  |
20--c  e--|  |  |  |
     b    |  |  |  |
     |    |  |  |  |
     r    |  |  |  |
5----+-|<-|  |  |  |
          |  |  |  |
7---------+--+--+--|
########  |  |  |  |   ############
          |  |  |  |
          A  B  C  D

Notes
Wire A is not connected to the PC, it is only used to prevent TNCs talking
together.

Wires B,C,D can go on to more TNCs with THENET installed.

The diodes  -|<-  or  ->|-  are 1N914 etc

The transistors  c  e  are 2N3904
                   b

The resistors are all 10k

The  +  is a cross over, and the  ---|  is a join

At the computer end you MUST run BPQ software. If BPQ is turned off, the TNCs
cannot talk to each other.

I have 4 TNCs connected in this way and it works well. The main reason I use
this is because my radios + the TNCs are in the loft and the PC that runs
GB7AAA is downstairs. This stops all the QRM I was getting on 6m + 4m from
the PC and I only have 3 wires to connect it all up...

73 de Paul G0HWC @ GB7AAA

With acknoledgements to Robin, G8VPQ for the technical information.



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