[Elecraft] KAT2 problem.

[John Webster]

Final Report on KAT2 Problem.

Thanks to all those who replied to my query.
Your assistance helped solve the problem.
Here is what I learned.

1. I had made no construction errors, and there
was no faulty component.

2. To try to adjust C55 for null using the K2's
 LCD display (as per manual) is almost an
impossible task.  There are timing delays in the K2
that make it a tough task.

3. You CANNOT use an antenna in place of a 
dummy load.  Even if you use a tuner & adjust
the match to read 50 ohms resistive with an
antenna analyzer (MFJ 259B) at the point the
K2 would be looking at.

4.  Don't think you can slip down to Radio Shack
on the week-end and get a couple of 100ohm 
Carbon Film 2 watt resisters and make-up a dummy 
load.  They don't have them. Buy a decent dummy
load.  No self-respecting ham ought to be without
one. [Blush]

What I did that worked.

1. Radio Shack did come to the rescue in the end, in
an unforseen way.  On a whim, I noticed they had
over in the computer section, a neat shiny, stubby
BNC connector they call "50 ohm BNC terminator"
Used for terminating network connections, the thing
is obviously a miniature "dummy load".  But how 
much power can it handle?  Well, it turns out that
you can use it as a sort of "emergency low power
dummy load" if you are very careful.  I checked it,
and it shows a resistive load of 50 ohms across the
whole frequency range we are interested in.  If you
keep your TUNE's to just a few seconds at a time
and stay at 2 watts, it will not even get warm.  I tried
it for short bursts at 5w and could begin to feel it 
getting warm.

Again, this was an EMERGENCY solution that
worked for me.  Cost $3.

2. Use an analogue meter (VOM) and connect
it between ground and the non-ground side of 
R2 (not the wiper)--that is the junction of R2 and
D2.  Simply use an alligator clip to the leg of the pot.
Now C55 can be nulled without problem.  Mine
came as close to 0 as I can read on the .25 volt
scale!  When done, the K2 LCD read 004.  So I'm
very satisfied with this method.
[Thanks to Tom, N0SS and others, for this VERY
helpful suggestion]

I finally got hold of a local ham who very kindly
allowed me to come over and set up the power
settings with an accurate watt meter and REAL
dummy load.

When done, both REAL dummy load and RS $3
special showed 1:1 across all ham bands (actually
slightly higher 1.1 or 1.2 on the highest bands, due
to stray capacitance, as the manual indicates).  

And my random length long wire "enemy of all
switching power supplies" special can be tuned on
all bands to close to 1:1, except for 30 and 17 where 
it is about 2:1.

I'm satisfied.  Another fine piece of engineering
from Elecraft, and another case of outstanding
support from the list.

Thank you.

John, N6JW