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K2: KAT2 null adjustment

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Peter Wollan

K2: KAT2 null adjustment

According to the manual, it should be possible to adjust the null to
000, and it should be a broad null. On mine, it was extremely sharp,
and wouldn't get lower than 010, flickering to 011. Does this indicate
a problem? I went ahead and finished the installation -- the voltages
were fine, and the tuner seems to work just dandy.

I'm using a homemade dummy load, which seems to test out ok at least at
the lower frequencies, and I don't have a calibrated wattmeter (yet,
will borrow one soon).

Can/should the null be recalibrated, even though the resister has been
installed?

Peter N8MHD

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Don Wilhelm-4

Re: K2: KAT2 null adjustment

Peter,

Yes, the KAT2 can be nulled without removing R6, and yes, obtaining a
minimum reading of 10 or 11 is quite normal.

The reason for initially having R6 not installed has to do with checking
for shorts - but since the manual calls for a specific voltage range for
the check, the null procedure has to be completed first. There is no
need to remove R6 when rechecking the null.

If you have a good 50 ohm resistive dummy load and have an RF Probe, you
can calibrate the forward power with those tools, and they will be more
accurate than a run-of-the-mill wattmeter. P=V^2/R - Power equals (RMS
voltage squared) divided by the Resistance. Several trials should
result in a well calibrated wattmeter inside the KAT2.

73,
Don W3FPR

Peter Wollan wrote:

> According to the manual, it should be possible to adjust the null to
> 000, and it should be a broad null. On mine, it was extremely sharp,
> and wouldn't get lower than 010, flickering to 011. Does this indicate
> a problem? I went ahead and finished the installation -- the voltages
> were fine, and the tuner seems to work just dandy.
>
> I'm using a homemade dummy load, which seems to test out ok at least at
> the lower frequencies, and I don't have a calibrated wattmeter (yet,
> will borrow one soon).
>
> Can/should the null be recalibrated, even though the resister has been
> installed?
>
> Peter N8MHD
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>

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Leigh L. Klotz Jr WA5ZNU

Re: K2: KAT2 null adjustment

Administrator

In reply to this post by Peter Wollan

Peter,
One easy check is to make sure all relay pins are soldered. It is easy
to miss one, especially near one of the board vias (empty through-holes0
and a missed coil pin gives you a 50% chance of having the relay stuck
such that an extra L or C is on the at all times.
Others will respond with a more thorough checklist, but this is a really
easy visual check.
73,
Leigh/WA5ZNU
On Sat, 11 Aug 2007 6:27 am, Peter Wollan wrote: