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Re: [TowerTalk] re; Whiskers growing where you cannot shave them

To: <Jamesnf@aol.com>, <N6TA@arrl.net>, <boblombardi@cfl.rr.com>,<towertalk@contesting.com>
Subject: Re: [TowerTalk] re; Whiskers growing where you cannot shave them
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Sun, 3 Apr 2005 11:54:42 -0400
List-post: <mailto:towertalk@contesting.com>
Thanks Jim,

> BTW, all this was going on in a plant manufacturing 2-way
radios and cell
> phones.  We were using fine pitch smt ic's and close
spacing on board traces.


Then that's almost certainly why I've never seen a whisker
problem (outside of vacuum caps and vacuum tubes) in all my
years of messing around with this stuff.

In a tube or vacuum cap the whisker will greatly reduce
voltage breakdown because it concentrates the electric field
at the sharp point. It's fairly easy to burn the whisker
off, but if an arc starts while high current is available
(like discharging filter caps in an amplifier, or running
kilowatts in a matching or phasing system) it can actually
destroy components. The least it does is make an annoying
pop or bang, depending on available energy and the impedance
of the discharge path.

It makes more sense to me now. Heck, I always have to watch
PC board suppliers because they try to charge a premium for
close trace spacing when the closest I normally get on
layouts is .035 inches. I live in a wide spaced trace world
for now.

Probably the only concern for Hams and Ham antennas is in
the cell phones we use to order beer and pizzas that
maintain our seat padding.

Thanks,
Tom




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