[Elecraft] K2 Lo P

[Don Wilhelm]

Jay,

Don't tear into it too quickly.  Make some methodical tests first.

TRUISM:
If you successfully obtained a null while connected to a dummy load, and 
then left that same dummy load connected when you checked the SWR 
reading, the SWR will read 1.0 - if it does not, your null was not correct.
End of truism.

An SWR of 9.9 usually indicates either a short or an open circuit - 9.9 
is the highest SWR that is indicated by the K2.  Be certain the coax 
cable to your dummy load is good as a first step.
You could not have achieved a proper null if you have either an open 
circuit or a short condition, so you will have to do the null again.

Before doing anything else, make a couple of 'sanity' measurements.
Set the ATU menu to CALP and set to ANT1, then power off and remove the 
input coax to the KAT2 from the RF Board.
Measure the resistance from the input coax center conductor to the 
center conductor of the ANT1 jack - it should measure zero ohms.  Also 
measure resistance from the center conductor of the ANT1 jack to the 
shell - that should be very high (even infinite).  If these measurements 
do not check out properly, the path is not intact through the wattmeter 
and relays K17 and K18 and that problem must be found before proceeding.

If the above checks were good, then connect the dummy load to ANT1 and 
measure the resistance from the center conductor to the shield on the 
input coax (with the input coax still unplugged) - it should measure 50 
ohms.  If not, stop and find the problem.

If all is well down to here, then put the KAT2 input coax back in place 
and try the null again.  If it anywhere near normal, the slot on C55 
will be within 30 degrees of parallel with the long side of the KAT2 
board.  If it is perpendicular to the long side of the board, then the 
capacitor is either at its minimum or maximum capacity point and you 
have a problem with T1, R3, R4, C54 or C55.  As usual, T1 is the most 
likely suspect.

73,
Don W3FPR


Jay Sissom wrote:
> Oops, I sent this to Don by himself, but thought I should send it to
> the list just in case it helps someone.
>
>
>
> Thanks Don, just an update. I re-nulled C55 and it nulled fine.  When
> I checked the voltage at U4 pin 1, it was 2.8V which was a little low.
>  Then I set R1 & R2.  After doing that, the SWR into a dummy load is
> 1:9.9.  I'll take the antenna tuner apart and look to see what I can
> find.
>
> Thanks & 73
> Jay
> W9IUF
>
>   
>