[Elecraft] Re: [Questions for KAT100 Gurus

[Wayne Burdick]

Hi Lee,

Lee Buller wrote:

>    ...noise when it tries to make the match....

Very large, conservatively-rated relays are used in the KAT100, and they make
noise. Tuners with similar ratings that are relay-switched sound about the same.
Some damping could be used, but we haven't tried this yet. Fortunately, the
KAT100 saves all of the L/C settings on each band, so you should only rarely
need to go through a full re-tune.


>    ...C of 2.10.  I am assuming that means 2100 pf?

Yes.


>    Anything on the E for Error above 200 to 256 is OK?  Under 199 is a real error?

200-255 are algorithm tracing numbers. Report anything under 200. Both are for
our use if we ever need to change the firmware.


>    And if it says T168...it actually went through 168 different tries at getting the SWR down? 

Yes.


>    What happens if it cannot find a match?  

The LEDs will all stay lit (indicating SWR > 5). But it will still select the
best possible L/C combination, and this will be reflected in the SWR reported
back to the K2's LCD. 


>    I have been looking at the manual and it talks about a manual operation.  

There's no way to adjust the tuner manually. I searched the manual and didn't
find any references to this, so I'm not sure what you're referring to. If you
want to use a separate, manually-tuned antenna tuner but still have the KAT100
in line, you can put the KAT100 into CAL mode (L and C = 0). It will then still
report power and SWR during tune up and show SWR on its LEDs, which could be
useful with a separate tuner that lacks metering.


>    Does it remember the settings for each mode and each VFO?

It remembers the L/C settings for both antennas, on every band. But it doesn't
save settings on a per-VFO basis or based on the part of the band you're tuned
to. This is usually not a problem because it can quickly re-tune between
different parts of the band, and on higher bands it would rarely need to do this.


>    I have a SignalCrafters SWR bridge.... match is not quite there...

If the KAT100 says the SWR is 1.0:1, it's probably quite close to this, although
like most SWR bridges, the KAT100's measurement accuracy is reduced as reflected
power decreases to nearly zero. This is due to nonlinearity of the detector at
low RF voltages. But a small mismatch will have a completely negligible effect
on radiated power anyway, which is why some auto-tuners stop trying at 1.5:1.
The KAT100 always shoots for 1.0:1.

That said, you may not have the bridge nulled perfectly. It's best to perform
the nulling operation using an analog voltmeter. The two pots generally have
little effect on SWR measurement accuracy and can be simply matched in their
setting by measuring the resistance from wiper to ground (with power turned off).


>    Also, when I nulled at the cap in the SWR bridge, I could not get it to ZERO.

As long as you got it to its lowest point, it doesn't matter if it was all the
way to zero--unless you have an assembly error in the bridge. But I doubt it.
Residual RF detection (at either the bridge itself or the meter) often makes a
zero reading impossible to achieve..


> Other wise, its working fine....

Great!

73,
Wayne
N6KR