[Elecraft] Digital mode power handling for KAT3

[Rick NK7I]

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 <ab7echo at 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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