[Elecraft] K2 ATU alignment: stumped

[Tom Hammond NØSS]

Andy:

>Hope everyone had a great Christmas! I am building the ATU for the K2, and
>all has gone well up to page 16, where we start the alignment. I set the Pwr
>for 5.0, VFO for 7100.00, and have rotated the resistors and C55 several
>times to "loosen them up". However, when I go to CalN (null) adjustment for
>the ATU, the reading is jumping all over the place. It may settle for a
>short time on say 011, but the slightest touch on C55 drives it wild -- and
>some positions never settle down: the reading may jump from 028 to 000 to
>042, ...

Sure does... I just helped a friend last week and saw the same thing...

1) Use 1W...! Easier to get at the null.

2) Hang an ANALOG (e.g. real METER) meter across the REFL line and do the 
(at least gross) NULL adjustment using the needle indication from the 
meter. Then go back and do some fine tweaking with the digital display, IF 
you feel it's necessary.

>Am I missing something somewhere? I have the Errata where it says you may
>get 001 or 002 instead of 000, but when I get near the 000 with say 098, it
>will not stay there. It doesn't seem as if it can be adjusted. The solder
>joints on the FWD/REV pots and C55 look good, and everything has checked out
>to this point. One note: the plug P8/J8 connection is VERY tight, but it
>also passed all checks, as did all the Lx and Cx stuff.

If you have one of the newer KAT2 kits, you will probably NEVER come CLOSE 
to seeing 000, 001 OR 002... about the VERY BEST you can hope for is 
something in the range of 006 to 012, with 010 or 011 being the NORM 
(emphasis added here!).

This does NOT mean you have anything 'out of adjustment' and is mostly the 
result of a capacitor value change at C50 and C51 (they were changes from 
.01uF to .001uF).