[RFI] RF Quiet Laptop for Mobile Console?
ka5s at earthlink.net
Fri May 19 04:44:27 EDT 2006
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.
>From: doc <kd4e at verizon.net>
>Sent: May 18, 2006 2:12 PM
>To: RFI List <rfi at contesting.com>, tvi-rfi-emi at 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
More information about the RFI