[Elecraft] KAT100 Problem

[Don Wilhelm]

Dick,

Are you doing the component tests (C5 to C6 for example) into a dummy 
load or into your antenna.
Trying that test into an antenna just adds a lot of other unknowns into 
the formula - use a dummy load.
Not only that, check the dummy load and the coax going to it - if you 
have an antenna analyzer, put it on the end of the coax that you are 
connecting to the KAT100 and see what the impedance is - it should be 50 
ohms resistive and zero ohms reactive (or very close). Bad coax is a 
frequently overlooked problem spot as are PL-259 connectors that are not 
fully tightened.

In other words, reduce the system to its bare essentials when doing any 
tests.
With the known good dummy load and coax, now try the manual instructions 
again.
If you get the same results on 20 meters, drop down to 40 meters and try 
the same test.  Often the switch between one capacitor and another will 
cause the SWR to 'go offscale' on a higher frequency, but be just fine 
at a lower frequency.
The jump in capacity between C5 and C6 is quite large - C5 is 150 pF 
while C6 is 300 pF, and that is a LOT on 20 meters.  Your results when 
dropping down to 40 meters seem to be in line with reality.

There is an alternative test (not in the manual) that you can do if you 
have a capacity meter.  Connect the capacity meter between the center 
conductor and the shell of the input jack.  With C0 selected, zero the 
meter (or record the stray capacitance shown), then cycle through the C1 
thru C8.  The capacitance should approximately double with each step 
upward in Cx.  If you are not using a capacity meter that has a zero 
capability, subtract the capacitance measured at C0 from the reading at 
the other capacitors to arrive at the real capacitance value that the 
KAT100 is connecting.

Yes, your RF-in-the-shack can be confusing things a lot.

73,
Don W3FPR

On 7/7/2013 7:06 PM, richardjwiltgen at aol.com wrote:
> I have encountered difficulty with the KAT100.  I am pretty sure the problem resulted from RF feedback in the shack from a Zero-Five flagpole antenna with an unun at its base, an ugly balun with Polyphaser ground after 80 feet of coax prior to entry into the shack, and a Balun Designs isolation balun following the 20 feet or so of coax that enters the shack.  The isolation balun is inside the shack for stealth reasons because of a very intrusive HOA.  Thae KAT100 would not tune the antenna or a dry dummy load on 20 meters. It will indicate a high SWR and the K2 registers a hot power amplifier. If I run it for a while, the RF gets into the radio and the other bands may be affected.  As a consequence, I will eventually move the isolation balun between the KAT100 and the K2/100 and place another one on the line that leads into the shack.  I tested the components as stipulated in the manual.  When I switch from C5 to C6, the SWR jumps from 2.5 to off scale (9.9) on 20 meters and
>   1.4 to 7.0 on  40 meters.  Based on the knowledge and past experience of others,  does it seem reasonable to assume that C6 is defective and the cause of the problem?  Many thanks beforehand for any advice you folks have to offer.  Vy 73, Dick, K8RBW.
>