Re: KX3 antenna tuner intermittent operation

Posted by Dave KW4M on Nov 27, 2016; 4:15pm
URL: http://elecraft.85.s1.nabble.com/KX3-antenna-tuner-intermittend-operation-tp7573335p7624286.html

I experienced a related issue with the KX2 ATU during the CQ WW contest this weekend.

After a frequency change during search-and-pounce, I would send my call, KW4M.  What was actually transmitted was KM4M.  The first dit in the second letter was chopped off.  I could hear what sounded like a relay click when this happened.

This happened on multiple occasions.  Subsequent transmissions were fine until another significant QSY.

The CW keying was computer-generated at 25 WPM.

-Dave


KW4M

wayne burdick wrote

Ralf,

Like the K3's ATU, the KX3's ATU stores up to 32 segments of LC data on each band. On 160 m the segments are 10 kHz wide (1800-1810, 1810-1820, etc.). Anytime you move the VFO into a new segment, then transmit, the ATU will reload the last-used LC data for that segment (or the closest segment for which data has been stored). If the data is the same as for the previous segment, nothing will change. If it's different, the LC data will be sent to the ATU's relays, and the "ATU" icon will flash.

Note that this will not happen until after you pause 1/2 second in your transmission. This way we don't mess up the timing on your first transmission if you were in CW mode.

My guess is that you moved the VFO into a new segment where you had previously tuned up into a different load, so that the LC data was a little different.

There are a couple of things you might want to do. If you changed antennas, you can optionally go into the ATU MD menu entry and hold CLR to erase all of the ATU LC data for the current band. Then retune the ATU in the part of the band you use, as needed (when SWR is high).

A more exhaustive approach might be useful if the antenna's SWR varies widely across the band (often the case on 160 m): Tune up the ATU ahead of time on every segment. That is, set the VFO to about 1805, tune the ATU, then move to 1815 and tune the ATU, etc. This is usually overkill, but it would optimize the LC settings ahead of time for a narrowband antenna.

You might try the above and let me know what happens.

Another possibility is that you simply have very high SWR resulting in RFI. If that were the case, reducing power to a couple of watts would reduce RFI and the symptoms would go away (or at least be different). My guess is that this is not what's happening; you're just seeing the ATU retune in new segments.

I'll also send you our latest field-test firmware which is likely to be released as beta later today (rev 1.47). It has significant stability improvements that could have some bearing on ATU-related problems.

73,
Wayne
N6KR


On May 2, 2013, at 1:16 AM, DL6OAP <[hidden email]> wrote:

> Hi,
>
> I received my KX3 one week ago and had some fun yesterday with it and an
> end-fed wire antenna roughly 20 mtrs long. The ATU worked great on getting
> the SWR down to 1:1 (not on 160) but there was an issue that concerns me:
> while transmitting, the ATU icon in the display went flashing and the SWR
> changed….


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