The answer is in the results of simple questions:
Who, if any, has had their KAT3 fail and for what cause? What was
actual (r,x,c) antenna load, that was being attempted?
I suspect the failures are low, it's smart enough to quit trying if the
match is too extreme. The same components (mostly) are used in the
KAT500 (just larger sizes) which also has a low failure rate.
Instead of guessing, answers of actual failures would provide data points.
73,
Rick nk7i
On 10/13/2023 11:56 AM, David Gilbert wrote:
I am reasonably certain that the KAT3 can handle 100 watts for a
lengthy period to time (enough for normal FT8 purposes) if the SWR it
is trying to match is low enough. But the original query didn't say
how high an SWR he was trying to match. The KAT3 is certainly capable
of matching some pretty high SWRs (well over 10:1), but the question
is how long can it push 100 watts into an SWR that it could otherwise
normally handle at lower SWR.
Another factor is the phase of the impedance the KAT3 is trying to
match. A high SWR could present either a capacitive load or an
inductive load to the KAT3. In one case it could result in high
currents within the KAT3 ... in another it could mean high internal
voltages.
So the real question is ... can the KAT3 survive for X amount of time
when pushing 100 watts into a high SWR at most any phase? I can
pretty much guarantee that nobody knows the answer to that question.
I wouldn't be at all surprised if the KAT3 could handle 100 watts into
a high SWR for periods of time that were comfortable for FT8 if the
phase of the load impedance resulted in higher currents. I'm not so
confident about that if the phase gave high voltages. Heating takes a
bit of time to be destructive ... voltage breakdowns and arc overs
happen very quickly.
73,
Dave AB7E
On 10/13/2023 8:03 AM, Bill Frantz wrote:
I have frequently used my K3 at 100 watts with FT8 and RTTY. I
haven’t had anything which would indicate that components are getting
overstressed (e.g. bad smells).
Now, I don’t think I have given a full 100 watts when something isn’t
connected in the antenna system, although the KAT3 does “match” an
open antenna line. Since in that situation, it clicks for a long time
before coming to a “match”, I tend to notice that there is a problem
before applying full power.
73 Bill AE6JV
On Oct 12, 2023, at 23:42, David Gilbert <ab7e...@gmail.com> wrote:
I thought I was clear, but apparently not. It is 100% duty cycle
for 13 seconds, and zero for 2 + 15 seconds. "Duty cycle" is all a
function of what period of time you choose to integrate over. Lots
of components if heavily over stressed can go south in 13 seconds.
Whether that is the case with the KAT3 is unspecified as far as I
can tell.
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