Cantankerous KAT-100-1

[Roy Morris-6]

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:
L0    1.0
L1    1.0
L2    1.1
L3    1.2
L4    1.7
L5    4.5
L6    9.9
L7    9.9
L8    9.9

C0   1.0
C1   1.0
C2   1.0
C3   1.0
C4   1.1
C5   1.3
C6   2.0
C7   5.0
C8   8.7

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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[Don Wilhelm-3]

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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