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Re: [RFI] RF Quiet Laptop for Mobile Console?

To: RFI List <rfi@contesting.com>,tvi-rfi-emi <tvi-rfi-emi@mailman.qth.net>
Subject: Re: [RFI] RF Quiet Laptop for Mobile Console?
From: Cortland Richmond <ka5s@earthlink.net>
Reply-to: Cortland Richmond <ka5s@earthlink.net>
Date: Fri, 19 May 2006 04:44:27 -0400 (GMT-04:00)
List-post: <mailto:rfi@contesting.com>
Not long ago, I tried running digital modes using a KAM-XL hooked up to a 
Fujitsu P5020 "Lifebook" laptop. This actually worked well -- quieter than my 
e-Machines T2642 -- until I hooked up a power supply.  Both the DC and AC 
supplies are of course switchers, putting out 16 volts the computer needs.  I 
am considering tapping off 16 volts from the unregulated part of an analog PS 
for this application when at home. Meanwhile, carrying an extra battery gives 
me almost 8 hrs of computer life, and an optional extended-life battery can 
replace the CD-drive  for (IIRC) about 11 hours total, if that can be accepted. 

I have not gotten "a round tuit," but I suspect the computer might still work 
on 12 volts, if not charge the battery from it; the battery voltage is only 
10.8 volts.  Some years ago there was an article in a Ham magazine about one 
Amateur who modified a laptop's battery to accept 12 volts. Among other things, 
this required adding a voltage regulator inside a battery pack.  Alternatively, 
there is a Ham (name, call forgotten) who builds and sells RF-quiet switching 
power supplies for such applications.  Or you can yourself shield and filter 
one built by the computer manufacturer.

I am a member of the IEEE emc-pstc mailing list; very recently there was a 
posting to that list, which is EMI, EMC and Safety design and test 
professionals, about being unable to find *any* currently sold Class 
B-compliant computer to use testing other devices to FCC Class B limits.  This 
has been a real problem for some time, but with the FCC pretty much out of the 
Part 15 enforcement action (thanks, Congressman!) we are on our own.

When I bought my present laptop, I carried a Yaesu VR-500 receiver into the 
store and looked at interference the display models generated in the HF region. 
 The VR-500 in WFM mode has a spectrum display up to 6 MHz wide.  This Fujitsu 
is  pretty quiet. It is also no longer sold -- and who knows if another of the 
same model would be as quiet?  Still, I do recommend a portable receiver when 
shopping for a computer; it can help keep you from buying a real screamer.

Incidentally, energy efficiency regulations are beginning to force analog power 
supplies off the market.  


-----Original Message-----
>From: doc <kd4e@verizon.net>
>Sent: May 18, 2006 2:12 PM
>To: RFI List <rfi@contesting.com>, tvi-rfi-emi@mailman.qth.net
>Subject: [RFI] RF Quiet Laptop for Mobile Console?
>Can anyone recommend a laptop for this context?
>1.  Sitting on top of a metal box that will house
>     HF & VHF-UHF gear as well as a scanner.
>     (must not radiate tons of RF noise)
>2.  Mobile in a van that will be on some rough roads.
>     (needs to handle dust and vibration well)
>3.  Runs natively from 12vdc.
>Thanks! & 73, doc kd4e  http://bibleseven.com
>Ham Links: http://bibleseven.com/hl.html
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