[TenTec] Is there a beefier 2N5301?

[Gary Hoffman]

A further comment is that many TEC coolers are used in fact as
dehumidifiers.  As such, they are available from the factory sealed against
water.  You must take further steps of course.  But it is not so difficult
as may at first appear.  You can easily arrange a radio that you can pour
water on the rear heat sink with no ill effects.

Gary


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
To: <tentec at contesting.com>
Sent: Tuesday, March 06, 2007 9:30 PM
Subject: Re: [TenTec] Is there a beefier 2N5301?


> On Tue, 2007-03-06 at 19:50 -0500, Gary Hoffman wrote:
> > It is interesting that most of us don't know how important the heat sink
> > goop is, and how much of the heat transfer takes place through it.
> >
> > The two metal surfaces (heat sink and transistor) even if machined quite
> > flat and smooth actually touch microscopically at a very few tiny
points.
> > That is the limit of the metal to metal transfer.  Even if you work
really
> > hard at it, that is the best you can do.
> >
> > The rest of the space is filled with air, and air is an excellent
insulator.
> >
> > To fix this problem, one approach is to use conventional heat sink
compound.
> > These common compounds use a passivated aluminum oxide extremely fine
powder
> > suspended in a petrochemical.  This compound fills the air gaps and the
> > aluminum oxide conducts the heat far better than the air would have.
> >
> > In extreme applications, a better heat sink compound uses extremely fine
> > silver in the place of the aluminum oxide, for many times better
results,
> > but at the expense of having the compound be electrically conductive
which
> > can cause many issues.
> >
> > So, generally we use the aluminum compound and it works really well.
> >
> > To go beyond that, you have to turn to the heat sink itself.  Make it
> > bigger.  Make it Copper.  Give it more and larger fins.  Blow air on it.
> >  Or - if you really want to do it right, use a TEC for active cooling
and
> > make that heat sink really really cold.  Just short of the dew point of
> > course.  And much more practical than liquid cooling.
>
> So today in Iowa that heat sink could be cooled to 15 F but on a warm
> summer day in Houston, the dew point might be 95 F so you would have to
> include a dew point sensor to pick the cooling point, or a moisture
> sensor on the heat sink to detect the dew...
> >
> > TECs really rock when used properly in this manner.
> >
> > 73 de Gary, AA2IZ
> >
>
> -- 
> 73, Jerry, K0CQ,
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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