Path: utzoo!attcan!uunet!timbuk!cs.umn.edu!ub.d.umn.edu!rutgers!sun-barr!cs.utexas.edu!samsung!rex!wuarchive!usc!ucsd!ucbvax!hplabs!hpfcso!rrd
From: rrd@hpfcso.HP.COM (Ray Depew)
Newsgroups: comp.sys.handhelds
Subject: Re: HP48sx Transfers
Message-ID: <7360010@hpfcso.HP.COM>
Date: 19 Oct 90 18:31:19 GMT
References: <1990Oct17.003101.10274@nmt.edu>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 19

It sounds to me like the problem is your unshielded cable.  When you're 
downloading to the 48, your Coco is putting somewhere between 5 and 12
volts on the line, so your signal-to-noise ratio is pretty good.  Going
the other way, though, your 48 is only putting out about 4.2 volts, so
the S/N ratio is somewhat worse.  Considering the possible sources for EMI/
RFI in the vicinity (monitor, power supplies, flourescent lights, disk
drive?), I'm not surprised that you're having trouble.

A lot of people ignore the shielding and get away with it, but you're just
one of the lucky ones who needs it.  Try wrapping your homebrew cable in
aluminum foil, or even window screen.  Connect it to both the Coco and the
48.  I know it seems like a pain in the wazoo, expecially since you've
already made the cable.  but it should do the trick for you.

Good luck.

Ray Depew
IC's by Bill and Dave   
rrd@hpfitst1.hp.com