[Elecraft] KPA100/KAT100 SWR Fault

[Don Wilhelm]

Doug,

I suspect that one or both of  the wattmeter diodes in the KAT100 are 
fried.  It would be a good idea to check those in the KPA100 as well.
KAT100 D1 and D2 and KPA100 D16 and D17.

73,
Don W3FPR

Douglas Furton wrote:
> Dear Reflector,
>
> Hello again.  I wish I wrote more often to say how good my K2 and KPA100 with KAT100 are working, but I don't.  They have been working great.
>
> I built a KPA100 and KAT100 into an EC2 enclosure.  Everything has worked well for quite some time now (~1 yr.).
>
> Today, I write with a problem: I fired up my rig and find that the SWR indication on the KAT100 is faulty.  Here are the symptoms, transmitting into a dummy load:
>
> First, something that works properly: when I dial up the output power without transmitting, the PWR range LED switches from low to high at ~9 watts.
>
> Then -- with the ATU in CAL mode -- when I hit TUNE with the power set to the low end of either the low- or high-power ranges none of the SWR LEDs light.  With the K2 still in TUNE mode, as I slowly dial up the power, suddenly all of the SWR LEDs light.  This happens if I start at 1 watt and tune to about 5 watts; and if I start at 10 watts and dial up to about 50 watts.
>
> When I hit TUNE at about 1 watt and dial up the power past 9 watts, the SWR LEDS come on at about 5 watts, then I hear a relay click in the KAT100/KPA100 indicating it changed power range at about 9 watts, but the PWR range LED does not flip from low to high and all the SWR LEDs remain lit.
>
> I also get erratic HiRFL messages on the K2 display, but not reliably when all the SWR lights come on as I described above.
>
> The K2/KPA100/KAT100 currents are normal.
>
> Otherwise, the rig seems to perform as it did before this fault appeared.  Output power is good, and it all seems to transmit into an antenna that I know is resonant and good on 20 m.
>
> What should I check out first?
>
> It might help to know that between the time I noticed this problem and the last time I used the rig, there was a thunderstorm in my area.  While I normally set my antenna switch to ground the antenna and project my xmitters, I did not do so this time.  My coax is grounded with two levels of lightening protection at the house: "cheap" lightening-arrester connectors outdoors followed by an alpha-delta coax switch with the "arc-plug" indoors.  The arc-plug is not "popped", or however you describe it -- it works fine still.
>
> Perhaps a lightening pulse of some sort caught something in the SWR section of the KAT100???
>
> Thanks to the community for help with this problem.
>
> Doug
>
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