[Elecraft] Generic words on temperature

[C.A. Jones]

Ahh, well, a few comments clarifications, from a guy with 38 years of
experience (HVAC/mechanical and controls engineering) with Carrier air
conditioning.

Opening comment (not really my area of expertise, but I do have moderate
relevant experience), the heat pain threshold is quite variable (between
individuals, and depending on time of day and LOTS of other factors), and
the touch test is probably not a reliable predictor of whether the radio is
"too hot".  My perception is that the Elecraft radios are thermally well
protected, but if really concerned, I think measuring temp with an IR
sensor and comparing it against published limits might be a preferred
approach to assessing it.

As to atmospheric pressure and altitude, these are really separate
variables.  While there is a functional relationship between them, it's not
so strong that for most normal activities (i.e. unless the plan is to climb
K2, Everest or similar) it shouldn't be a significant factor in the
discussion. And FWIW, temp generally decreases with increasing altitude,
which then of course lessens an overheating problem by increasing the heat
transfer driving delta-T.

As to whether it's better to install fans in a blow-thru or a draw-thru
configuration, there's no clear winner for this type of electronics cooling
application.  If condensation was an issue (it's not), the distinction
between these might become significant. Given that, the decision between
these would generally be based on the mechanical layout and on related
testing meant to insure that specific components remain sufficiently cool
in worst case conditions.

(BTW, no way one could hold his finger on a smooth 100C surface for 10
seconds, and no way that same surface at 100F would rise above the heat
pain threshold in 10 sec.)

Chris Jones  -  K2CZ



On Wed, Jun 30, 2021 at 9:37 PM Geoffrey Feldman <geoffreyf at comcast.net>
wrote:

> My rule of thumb is that if you can keep your finger on it for a second or
> so without pain, it's not too hot.
>
>
>
> The ambient temperature is really not the issue as much as whether heat is
> carried off.  I know it's hot in the pacific northwest but I think you can
> still enjoy your gear.  The larger issue is RFI from air conditioners.
>
>
>
> The environmental consideration many people neglect is atmospheric
> pressure.
> As altitude increases, there is less air to carry the heat away.  People
> sometimes install fans with an idea to sucking out the heat. This is
> actually wrong. The fan should blow ambient air in and the venting for it
> to
> get out should intend that pressure inside the case be a bit higher than
> the
> ambient pressure.  More molecules against the hot part, the better.  If you
> read the fine print on electronic specifications you will often (and should
> always) see an atmospheric spec with the heat spec.
>
>
>
> All the above is just rule-of-thumb of course.  There is a lot more to
> cooling electronics than the above but I think these are worth considering.
>
>
>
> Elecraft gear is pretty good at protecting itself as well. If your radio
> cuts out, it's doing its job of living for more fun later.
>
>
>
> W1GCF
>
> Geoff
>
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