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

[Don Wilhelm]

Rick and all,

Look for something in the antenna system that is arcing over above the 
80 watt level (or whatever level the problem starts).  Check every 
junction in your antenna system.  Your workaround may be OK, but the 
real fix may increase your antenna efficiency.

The other situation that will cause "bad behavior" above a certain power 
level (and on a particular band) is common mode RF coming in from the 
antenna and its feedline.  The SWR sensing circuits may "go crazy" in 
the presence of too much RF voltage.  In this case, the use of common 
mode chokes at the antenna, and possibly at other points along the 
feedline may be what it takes to "tame the beast".

73,
Don W3FPR

On 2/18/2012 5:14 PM, Rick Prather wrote:
> Ken,
>
> Yes, I have the same problem.
>
> Using a 102' doublet, open wire to a 4:1 outside the shack.
>
> Works great everywhere above 160M but on 80 the SWR goes nuts over about 75 Watts.
>
> My workaround has been to not run over 75 Watts  :-)
>
> Rick
> K6LE
>
> On 2/18/2012, at 1:40 , Ken<wa8jxm at gmail.com>  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,
>>
>>