[Elecraft] KXAT100 "Hunting"

[Bob McGraw K4TAX]

Candidly, I would be more concerned about exceeding the RF Exposure 
limits with this arrangement.  Perhaps the "Tuner issue" is an 
indication of such.  From your description, at 100 watts you will likely 
be way outside of the FCC limits of safe RF Exposure.

Now with that said, the amount of RF at the TUNE level is not such to 
confuse the tuner.  However at 40+ watts the RF back into the system is 
more than the system can accurately handle.  A bunch of #31 beads or #73 
beads, where "bunch" = 50 pcs or more, on the feed line at the antenna 
feed point and again a bunch at the radio. This may help the radio and 
antenna problem associated with the auto tune routine.  You may find the 
same treatment required on the DC power cable at the radio.

73
Bob, K4TAX


>>
>>
>> On 1/30/2016 12:54 PM, Dauer, Edward wrote:
>>> My KX-line tuner (the KXAT100 installed in the KXPA100 amp) recently
>>> started an odd behavior.  I wonder if anyone can help explain it.  When
>>> tuning into an indoor Buddipole set at resonance, the ATU finds a
>>> near-perfect solution when the power applied during tuning stays below
>>> about 40 watts.  With the ATU set in “auto” however, if the power out is
>>> higher than 40 watts the tuner hunts without stopping.  I have watched
>>> the
>>> SWR readings change, often going briefly to 1.0 or 1.1:1, but the tuner
>>> just keeps hunting, endlessly, even when the frequency is unchanged.
>>> Yet
>>> when it is first tuned at a lower power, either in Auto or Manual-tune,
>>> and the ATU is set to Manual, it stays at the solution perfectly well no
>>> matter how high the power goes.  I can live with this, just by tuning at
>>> low power and then switching to Manual, but I wonder why the Auto
>>> function
>>> works well up to a certain point but goes berserk at any power higher
>>> than
>>> that?  Is the higher ERP sneaking back into the control circuitry
>>> somehow?
>>>
>>> Ted, KN1CBR
>>> _