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Buying the Linux PC for Linrad use.

On 4 Jul 2003 at 18:50, Colburn wrote:

> I'd love to run a dc-dc power supply in an rf-tight tower case if
> possible, probably a Pentium 4 CPU  although a Pentium-M would save me
> fussing around the differences under Linux ... not to mention less
> heat and greater energy efficiency. ;-)
> My new laptop runs a Pentium-M 1.5GHz, it uses a good deal of
> magnesium alloy in the construction and is supposedly made by the
> "Rolls Royce" of laptop builders, Quanta.  It should arrive in a
> couple of weeks, will test it for rf leakage then.

Laptops can be pretty good because they are miniature and can be
well sheilded. My IBM Thinkpad 760 is a good example of this.
They can be difficult to add things to.

In my opinion, it is easy to RF bypass the AC power cord at RF.
This is likely much cheaper then a battery solution. Your solution will
depend on  frequency.

> My future location will be in a all-steel home (steel frame, roof, and
> outer wall covering with steel studs in the inner walls as well).  My
> plan is for all of the antennas to be located at least 50 feet from
> the radio room.  Am I likely to hear anything?  Cannot the RF leak
> from the PC to the receiver on power cables and from case to case even
> if the coax brings the desired signal from outside?

You did not mention what band you will be on or if it is EME or not.
In any case, most likely path will be radiation from the PC to the antenna.
Any other path is easily prevented. A mast mounted preamp will go a long
way to remedy more direct paths. I speak from experience on 2M EME.
Use well sheilded feedlines. Leakage test are easy. Start with a whip antenna
close to the PC to see what frequencies are present first. Most of the carriers
picked up by your array will be from your neighbors PC's and other electronic toys.

I have a few ideas for a Linrad PC now, but have not yet found any clear choices.
I may have to make some comprimises to hit the $250 price range.
It would be nice if someone took a look at the Walmart $200 Linux computer and
gave it thumbs up or thumbs down for Linrad use. It may not be real RF quiet, but
it would sidestep Linux installation and possibly help to resolve some compatibility issues.
Is there some resource that tells what has worked for others?
I see some terminology and labels mentioned for various hardware, but I have no
way to turn this information into a real PC that I can purchased at low cost.
Am I second only to Leif to try Linrad? A mistake here can be costly, so I 
am asking the group.

73, Jim Shaffer, WB9UWA.