[TRLog] Parallel Port Paddle Interface

[Jimmy Weierich]

Hi all,

I am building an interface box to connect the PC to the rig (TS-850) via
the parallel port and provide switching for the SoundBlaster input and
outputs for using SBDVP. I also want to connect my Bencher paddle via the
parallel port. If I understand the suggested interface circuit in the
manual correctly I need to:

1. Connect a 10k ohm resister from pin 12 (Dit paddle contact input) to the
dot connection of the paddle cable.

2. Connect a 10k ohm resistor from pin 13 (Dah paddle contact input) to the
dash connection of the paddle cable.

3. Connect pin 14 (+5v pullup) to the common (ground) connection of the
paddle cable.

It looked straight forward until I noticed that pin 25 is labeled 'GROUND
for paddle'. Should pin 25 also be connected to the paddle common (ground)?
If so, it seems that I should isolate the jack for the paddle from the
interface box to prevent connecting the PC ground to the rig (via the mike
and cw input grounds) and station ground (the box will be tied to my single
point ground). I am using optoisolators on the PTT, CW and Record (for
SBDVP mike switching) parallel port lines, which also isolate the
associated pin 25 ground connections, to prevent RF problems in the PC. I
also have optoisolators in the existing serial interface for rig control.
The SoundBlaster connections will be isolated via transformers and jacks
that are isolated from the box. Maybe it would have been easier to use a
plastic box.

Or have I missed the boat completely here?

Call me cable confused,

Jimmy, KG2AU       <kg2au@earthlink.net>



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