[Elecraft] Sudden jump in SWR when power above 80 watts

[Don Wilhelm]

Ken,

A typical question when something like this arises is: "What does it do 
if you drive a dummy load?".

While another transceiver handling your antenna situation may also be 
good to know, it does not satisfy the question of "What does the K3 do 
when driving a 50 ohm resistive load."

The question of the difference in SWR readings between your Palstar 
tuner and the K3 cannot be answered without additional measurements 
driving a "dummy load" that produces a known SWR.

One thing you could do if you have an antenna analyzer is to tune the 
antenna tuner so the K3 indicates a 1:1 SWR - then remove the coax from 
the K3 and read the impedance on the analyzer.  Is it 50 + j0 or 
somewhat close?  If so, the K3 reading is correct, but if the SWR 
reading is 2:1. then your Palstar reading is correct.  If you have a 
substantial length of feedline between the K3 and the Palstar tuner, 
that might explain the difference in readings.

73,
Don W3FPR

On 2/18/2012 4:40 PM, Ken wrote:
> I am having trouble with my K3 tuner, the SWR jumps high when I turn it above 80 watts on 80m.
>
> At first I thought it was something outside but after replacing open wire feedline, balun, coax, I have come to the conclusion that the problem must be internal to the K3.
>
> The antenna is a 130' center fed dipole, fed with 45' of open wire to a 4:1 balun and then to the K3.   It tunes easily and works okay on all the bands but on 80m, when I up the power above about 80 watts, the SWR jumps up and the K3 shuts down with "HI SWR.
>
> The problem does not happen with my old TS-440, nor does it happen when I bypass the internal K3 tuner and use an external Palstar AT2K tuner.
>
> I don't believe I had this problem when I bought the K3 last December but then I might not have run the power up all the way either.
>
> Thoughts?  Am I missing something?    Has anyone else had this same problem?
>
> Another thing I noticed (is it related?) is that when I tune the Palstar to 1:1 SWR, the K3 shows a 2+:1 SWR.  If I use the K3 meter to tune the Palstar tuner, then the Palstar meter indicates a 2:1 SWR.
>
> Thanks,
>
> Ken WA8JXM
>