[Elecraft] Cantankerous KAT-100-1

[Don Wilhelm]

Roy,

There are 2 possibilities that occur to me.  First, yes, RF in the shack 
is a good possibility with an OCF antenna.  If you can add a 1:1 current 
balun (actually a line isolator) at the shack entry AND ground the coax 
shield at the point where the isolator is placed, that will go a long 
way toward minimizing RF in the shack.  If you have a W2DU type balun, 
use that, otherwise a coil of coax (about 7 turns 4 to 6 inches in 
diameter) will serve the purpose.  Run a short ground from the coax 
shield on the antenna side of the balun.  If you can create a zero 
length path to ground that is best.

The second possibility is that your KPA100 is suffering from the 40 
meter parasitic - that parasitic was the incentive for the KPA100UPKT, 
and if you do not have this latest change installed, I strongly 
recommend it.

73,
Don W3FPR

Roy Morris wrote:
> A little background info-- my KAT100-1 is grounded, it is connected to a Carolina Windom 80.  It will tune all bands from 80 through 10 meters and give a 1:1 SWR on all bands except for the phone band on 40 meters.  If I go from the CW portion (7040 Khz for example) straight to the the phone segment, the K2/100 will click, the KAT ANTENNA LED and POWER RANGE LED will flash brightly momentarily and the KAT becomes unresponsive.  The SWR is high when this happens, and VFO #2 reverts to VFO#1.  If, however, I sneak up the frequency in approx 20 Khz increments and tune the KAT at each increment, I can tune the KAT all the way to 7300Khz with a 1:1 SWR.
> I have run all the L and C menu parameters, and all the relays click as they should.  The parameters were checked starting on 10 meters and working down the bands.  There were no components that showed a too large or small change in relation to the others tested.  These were my readings on 40 meters:
> 
> I am beginning to think that stray RF is created by the off-center fed antenna, and the KAT MCU becomes RF saturated and cannot tolerate it on the higher portion of 40 meters.  If I tune the KAT into a 50 ohm dummy load, it seeks and attains a 1:1 SWR on all bands (including 40 meters).  Any comments appreciated.  Roy Morris  W4WFB  
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