[Elecraft] KAT100 Tuning Failure

[Phil Wheeler]

Be sure to check all the cables or try changing 
them out one by one, Jeremy.

Phil W7OX

On 7/17/15 10:05 AM, JeremyJones wrote:
> After many months of flawless operation, my KAT100 is starting to have
> trouble tuning up, particularly on 40 and 80M.  It even has trouble tuning
> up a 50 ohm dummy load on these bands.
>
> My normal setup is a 10W K2 with a KAT2, connected on the ANT 1 port to the
> AUX RF port of the KAT100 (mounted in an EC2 case with the KPA100).  This is
> internally connected to the KPA100.  The RF out from the KPA100 is then
> connected to the RF IN on the KAT100.  ANT 1 is connected to a DX-CC and ANT
> 2 is connected to an 80M Carolina Windom.
>
> The first signs of trouble started when the SWR LEDs only lit
> intermittently.  The ANTENNA and PWR RANGE LEDs lit and operated correctly.
> Gradually I stared seeing higher and higher SWR readings.
>
> In order to narrow down the issue, I removed the KPA100 from the setup by
> connecting the KAT2 ANT 1 port directly to the KAT100 RF IN.  I disconnected
> the power from the KPA100 and independently powered the KAT100.  I removed
> the Windom from ANT 2 and connected a 50 ohm dummy load to see how the
> tuning compared with the antenna and the dummy load.  On 80M the dummy load
> gets 3:1 SWR with the DX-CC tuning up the same.  60M gets 2.3:1 for both.
> 40M gets 1.2 for the dummy load and 3:1 for the DX-CC.  30M and up seem to
> tune ok.
>
> I tried doing the troubleshooting steps in the manual, starting with ATU
> INIT.  I scrolled through L0-L8 and C0-C8 and N1-N2 and the relays
> functioned for each.  I tried doing the individual test for the inductors
> and relays, but there was no change in SWR with multiple components, so
> either I was doing it wrong, or the fault is bigger than a single component.
>
> I've tried to be as detailed as possible here, so any help is appreciated,
> and if there are any suggestions or any other info required please let me
> know.  I'd like to get this back on the air as its my only radio!