[Elecraft] Digital mode power handling for KAT3

[David Gilbert]

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.
>