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[aprssig] RE: ICOM 706 MKii G Packet experience.

Dave Baxter dave at emv.co.uk
Mon Nov 26 09:30:04 UTC 2007


Hi..

I've just had a similar frustrating few hours over the last weekend,
trying to get PSK31 working on an old tosh laptop.

The same program (DigiPanV2) leads, radio etc (TS-870) worked fine with
another PC, but not the laptop I wanted to use (because it fits in the
space!)  Then, to my surprise it just started worked fine.  Shortly
after that (2 or 3 minutes) the laptop died with a dead battery.

The "Problem" was AC line and SMPS noise introduced by the lump-in-cable
PSU the laptop used, when it was actualy connected to and powered from
the mains.  The reason it all started working, was the AC lead fell out
of the PSU!  It would appear that despite the PSU having a "Ground"
connection to it's input filter, the DC out is fully isolated, but
poluted with all sorts of common mode noises.

Solution:  (as I have to use the AC supply with that PC) Run a separate
ground wire between the radio and laptop, connecting to one of the
exposed lugs of the (unused) printer port.   Guess an isolated interface
would do the job too.  For some reason, the audio I/O "Ground" is not
the same ground as the rest of the PC.  (There is about 100r between
them!)   There are no extra "noises" I can detect on the radio, so job
done perhaps...

At least now all the souncard based stuff I have seems to work OK on
that machine.  Pitty, as it's network port has just thrown a hissy fit
deciding it isn't going to work any more, and I cant use the built in
wifi cos' win2k doesn't support WPA.  Does it ever end?   (I want to use
HRD among other things remotely, hence the need for a working netowrk.
Plan B perhaps....)

If I ever get things sorted, I'll see if I can't put up a one way
i-gate, HF to APRS-IS.  Posibly lurking on 30m when nothing else is
going on.

Cheers.

Dave G0WBX.
This mail has been scanned by Palmer Cook Computer Services Limited.  www.palmercook.co.uk



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