K2 output @ 2 W

[Robert C.Abell]

Steve,
Re; your post to the reflector of Feb. 04.
I too am having difficulty getting my KAT2 tuner to work properly in
being unable to adjust C55 to move the reading from HI in CALn.
If you figure out what is wrong please advise me what you find.
I'm baffled, I built a KAT2 a year ago and had no problem. This one
built by a ham in Seattle, who is SK, is driving me nuts!
His assembly and soldering is above reproch, and the K2 &  KSB2 are
perfect except for the KAT2 which he never quite finished.
Any help you can offer would be appreciated.
Regards, Bob  VE3XM
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[Don Wilhelm-3]

Bob,

Did you follow all the instructions in the KAT2 manual for setting C55,
including the initial settings for the fwd and refl pots?  Are you using a
good 50 ohm non-reactive dummy load?

If the answer to those questions is YES, then you can try presetting C55 by
monitoring the voltage at the top end of the reflected pot - adjust C55 for
a minimum voltage and then see if you can complete the C55 calibration as
stated in the manual.

Another way to set C55 (actually more accurately than the manual method) is
to use two SWR=2 dummy loads - they must be pure resistances and you will
need one at 25 ohms and another at 100 ohms (use a very short length of coax
or just a double ended connector on these loads).  Set to CALS and set the
reflected pot to about mid-rotation - read the SWR value for both loads, if
they are not the same, adjust C55 a slight bit and try again until the SWR
reading is the same for both loads.  Once you obtain equal SWR readings for
both loads, set the SWR pot to read SWR = 2.  Then adjust the forward power
pot as indicated in the manual (but do not change the reflected pot.

BTW, this same method works great for not only the KAT2, but for the KPA100
wattmeter and the KAT100 wattmeter, although the method in the manual for
the KAT100 seems to work just as well for me and produces good results.

The dummy loads that I use:
I use 1% thick film power resistors for this purpose - Caddock MP930-50, I
have 4 of them, 2 in series for 100 ohms and 2 in parallel for 25 ohms, with
very short length leads to the connector - I mount them on a heat sink too
so mine can be used at powers up to 60 watts - YMMV.  One can use the 4
resistors later in series-parallel connection for a 120 watt dummy load when
you are finished.  The Caddock 50 ohm resistors are suposed to be
non-reactive up to 500 MHz, but be careful, I have found other values to be
capacitive, which is just as bad as being inductive.  The Ohmite TCH35P
series that I have checked seem to be truly non-reactive for all values, and
I use 3 of the TCH35P-150 resistors in parallel for a 105 watt 50 ohm dummy
load (I have put 150 watts into it for short periods), and my MFJ259
measures it as 50 ohms non-reactive through 70 MHz.

73,
Don W3FPR

> -----Original Message-----
>
> Steve,
> Re; your post to the reflector of Feb. 04.
> I too am having difficulty getting my KAT2 tuner to work properly in
> being unable to adjust C55 to move the reading from HI in CALn.
> If you figure out what is wrong please advise me what you find.
> I'm baffled, I built a KAT2 a year ago and had no problem. This one
> built by a ham in Seattle, who is SK, is driving me nuts!
> His assembly and soldering is above reproch, and the K2 &  KSB2 are
> perfect except for the KAT2 which he never quite finished.
> Any help you can offer would be appreciated.
> Regards, Bob  VE3XM

>

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