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Re: [RFI] Car laptop adaptors

To: <rfi@contesting.com>
Subject: Re: [RFI] Car laptop adaptors
From: "Jim P" <jvpoll@dallas.net>
Date: Sun, 11 Nov 2007 10:50:07 -0600
List-post: <mailto:rfi@contesting.com>
Just looked at the service info for an:

      IBM Thinkpad 380ED (updated w/Win98)

Reviewing the service manual the expected voltage
range out of the AC mains/DC power supply itself
(not necessarily the laptop's requirement) shows to
be in the range of +14.5 to +17 VDC with 'tip'

I'm going to try Vbatt straight straight into this laptop
because the inverter I've got is just too noisy on ten
Meters even!

The "+12V" line I will use runs directly to the battery
through a breaker nearer the battery - past experience
shows that in the neighborhood of 14 V can be seen
on a car electical system with engine running, which
is how I'll be using this laptop (moving map program
w/GPS rcvr). Ground will be to the frame in the
passenger area (GM B-body RWD car circa mid 90's)

I'm also going to disconnect the input Vbatt during
engine cranking.

JimP // WB5WPA//

----- Original Message -----
From: "Mel Crichton" <kj9c@iquest.net>
To: <rfi@contesting.com>
Sent: Saturday, November 10, 2007 11:08 AM
Subject: Re: [RFI] Car laptop adaptors

> I can tell you one to avoid: the universal adapter with numerous plugs,
the one I bought off Internet is Espow brand... about 20-25 bucks on
E-Bay... RFI even with ignition off. I tried the small TrippLite inverter
and managed to get it failrly quiet, but its noise increased ith ignition
> NN9K tells me that the really expensive one (about 150 bucks) made by Lind
Electronics is quiet, but I chose to buy a "12 volt" laptop instead.
> Just for fun, did you try your laptop on a 12 volt DC supply? Many WILL
work, even though the battery and AC supply are over 14 volts. I soldered a
cigarette lighter plug in parallel with the 19volt DC from the AC supply,
for a temporary fix. Will have a dedicated 12 volt AROUND the ignition
switch in the future.
> Mel KJ9C
> I suppose this is as good a place as any to ask whether anyone knows of a
> particular model of adaptor that will allow my 18V laptop to run off of 12
> VDC without creating RFI.

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