> From: "Lee Williams" <[EMAIL PROTECTED]>
> >I on the other hand I run my fans 24/7,why switch
> them at all? 28 years with the same PA transistors,
> I guess GE had the right idea! 73,Lee
But not with the same fans... bearings wear out and
extra fast if you're not keeping them properly serviced.
When's the last time you lubricated your fan bearings
and what type of oil did you use? What would happen
if the fan stopped working and you had a constant
key down condition?
> "Chuck Kelsey" <[EMAIL PROTECTED]> wrote:
> To me that makes more sense than running them for
> XX minutes after PTT.
Not at 3 off grid sites I own. All that blowing can
really suck the current (energy).
> > Chuck Kelsey wrote:
> > Maybe I'm missing something here, but I've never
> > subscribed to the theory of having fans run beyond
> > PTT. What purpose does it serve?
The heat transfer is not an instant event. Running the
fan past the tx off time allows the heat sink temp rise
to reverse (cool off) much faster. I have some very
smart Omega Temp Controllers, which are smart and learn
the heat transfer dynamics with an attached thermal probe
to calculate their best guess at on/off time values.
Takes about 3 days of operation for the controllers to
learn the thermal system. Much better to keep ahead of
the heat rise trouble curve.
> > While running the fans beyond the end of transmit
> > will cool the finals after the end of the QSO
> > quicker than without, why should it matter?
> >> Chuck
You try and keep the finals as cool as possible to
keep ahead of problematic thermal conditions. The duty
cycle of many rf solid state amplifiers is not 100%
unless you paid extra for it.
cheers,
skipp
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