[Elecraft] K3 Heat

[David Woolley (E.L)]

David Wilburn wrote:
> The fail temperature of the PA's is going to be well known and
> documented. Then a safety factor is added. But I seem to recall that

Things aren't as simple as that.  Mean time between failure tends to 
have an inverse exponential relationship with temperature, so any 
temperature higher than the minimum possible will compromise lifetime.

Even in terms of the manufacturer's never exceed temperature, this is 
specified inside the device, at a point where the thermal time constant 
may be quite small, so if you operator too close to TjMax, it may not 
need much of a transient to exceed it.

TjMax is typically a round number so is probably significantly less than 
the temperature at which the device sustains a phase change (e.g melts), 
and exceeding it may simply compromise MTBF.  (It may represent a point 
where a lower activation energy failure mode becomes dominant, or may 
just represent the point where the manufacturer considers MTBF 
unacceptable.)

> early comments on heat design criteria was for 10m key down, 100%
> duty cycle, without damage. But that is just the memory talking. YMMV


-- 
David Woolley
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