[Elecraft] KXPA100 + KX3 ATU High SWR

[Matt Maguire]

Make sure you are running the latest firmware. I observed similar symptoms some time back, and the root cause was resolved in a firmware update.

73, Matt VK2RQ




On Sun, Jun 28, 2015 at 3:16 PM -0700, "Don Wilhelm" <w3fpr at embarqmail.com> wrote:










Kyle,

I suspect you do not have a real problem.

It is much better to set the KXAT100 to MAN after having 'trained' the 
tuner in AUTO by tuning into each band segment (and band) that will be 
used with a particular antenna.
In MAN the KXAT100 does not automatically attempt to retune based of 
frequency and SWR.  It will remember the proper settings and switch to 
those if you change bands or band segments.  IMHO, it would have been 
better to label the AUTO position "TRAIN" instead, but we have what was 
decided when the labels were 'thought up'.

The condition is that there is a very short but finite time difference 
between when the forward power and the reflected power is measured.  If 
the forward power is measured when the power is low and the reflected 
power is then measured when the power is higher, the computed SWR will 
be higher than actual.  When the computed SWR is found to be high, the 
KXAT100 will try to retune (if in AUTO), or throw a fault condition (or 
both).

That usually happens more in SSB mode due to the difference in power 
created by the syllabic nature of speech, but it can occasionally happen 
during CW if the timing is such that the forward power is measured 
during an inter-element space and the reverse power is measured during a 
dit or DAH.

73,
Don W3FPR

On 6/28/2015 12:37 PM, Kyle Krieg wrote:
> All, hopefully someone can tell me what I'm seeing is expected behavior, as
> I've only had my KXPA100 attached to a end fed antenna at my house since I
> got it and it's work great.
>
> Yesterday I took the KXPA100 and KX3 out for field day.  We used two
> antennas, a Alpha Antenna vertical and a GR8V dipole, each attached to the
> KXPA100.  On the KX3, PA MODE is set to ON and TUN PWR is set to nor.  I
> have both an ATU in my KX3 and KXPA100.  The KXPA100 has always been in
> AUTO mode at home with no issues.
>
> When we tuned the AA vertical from the KX3, we had no issues, full power @
> 100W, low SWR readings.  Everything was great.  Again we are in AUTO mode
> since that's what it was last set to in my house.
>
> Out in the field, when hooking the dipole up, I used the same procedure as
> in my house, selecting a band/frequency, tapping the ATU TUNE button on the
> KX3 to allow the ATU in the KXPA100 to tune the antenna to an 1:1 or 1:1.2
> setting and then transmit.  Right after transmitting, 4 out of 5 times we
> would get a flashing SWR fault light on the KXPA100 that would last for 8
> seconds.  We switched coax and switched from ANT1 to ANT2 and received the
> same results with the dipole.
>
> Is this expected behavior?  I would think the KXPA100 would see that it has
> a tune setting in memory and setting it to Auto mode, it wouldn't throw up
> that SWR error?
>

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