[Elecraft] K2/100 and KAT100 odd behavior

[Jack Brindle]

On Jan 24, 2004, at 11:17 AM, Floyd Sense wrote:

> Here's an odd one I ran into last evening while operating in the 160 CW
> contest.  The problem I observed was that if everything was tuned  
> properly
> for the bottom end of the band (say, 1805) then moving higher up in the
> band, around 1845, resulted in a temporary high output situation.   
> While
> trying to pin this down this morning, I removed the amp from the  
> system and
> fed the K2/100 through the KAT100 to the dummy load.  With the K2 set  
> at 50
> watts on 1805, I hit the TUNE button and the KAT100 quickly showed a  
> 1.0
> SWR.  I then moved the VFO to 1845 and hit the key.  The output was 120
> watts!  Sending a string of dits, the output slowly stepped down  
> (discrete
> steps, not a gradual decay) until it again read 50 watts after maybe 15
> seconds.  If I repeat the test and first press TUNE at the new  
> frequency,
> the KAT100 doesn't cycle since the 50 ohm load hasn't changed, and it  
> shows
> a 1.0 SWR.  Hitting the key for a string of dits at that point results  
> in an
> output of 50 watts, as it should be.
>
> The KAT100 works properly in every other way, and there is no problem  
> with
> stray RF getting into cables.  The problem doesn't exist on any other  
> band.
> Any ideas as to what is happening?

Sounds like it is working normally. Antennas tend to tune rather  
tightly on 160m since a small change in frequency results in a large  
change in reactance. Your antenna is showing that change between 1805  
and 1845 KHz. So when you move the KAT up to the higher frequency, it  
will try to retune the antenna (in AUTO mode) when it sees RF.
When the SWR is something other than 1:1, the power reading will not be  
accurate. So after the KAT retuned the load, you again saw a correct  
reading.

Sounds normal to me...

- Jack Brindle, WA4FIB
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