ATU Question

[Bill Swindell - K1LED]

I have a K3/100 with the internal antenna tuner. The config is set to AUTO but it seems that I still have to press the ATU tune button to get the ATU to properly tune when I change bands. Is it supposed to be automatic or not?

[Don Wilhelm-4]

  Bill,

That is how it is supposed to work.  The "Auto" part of the tuner
function is that it remembers the tuning for 2 antennas for any band.  
To get it to remember that information, one must do a TUNE on each
antenna and on each band - after that, it is only necessary to change to
the band and the antenna, and the tuner will change accordingly.

The "automatic" tuner does not follow wherever you tune the VFO - you do
have to tell it which frequencies you wish it to tune to.

There are several variations on the meaning of "automatic".

73,
Don W3FPR

On 5/23/2011 10:23 PM, Bill Swindell - K1LED wrote:
> I have a K3/100 with the internal antenna tuner. The config is set to AUTO
> but it seems that I still have to press the ATU tune button to get the ATU
> to properly tune when I change bands. Is it supposed to be automatic or not?
>
>
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[Stan Gibbs, KR7C]

Bill,

From page 22 of the the K3 owners manual: "Up to 30 ATU settings are saved for both antennas on every band."  When you hit ATU TUNE, the K3 stores the tune settings for the KAT3 at the current frequency and for the current antenna.

In AUTO mode, if the K3 determines, on transmit, that the current KAT3 tuning parameters should be replaced, it will automatically load them when you key the transmitter.  You can tell this is happening because the ATU icon will flash briefly on transmit.

As to how the K3 determines whether to load new parameters, I would surmise that the K3 checks the ATU "map" each time you transmit, checking whether the current set of KAT3 parameters best match the current transmit frequency.  If it finds a better match, it loads them.

For example, if you have previously hit tune at both 14.020 and 14.170, have been operating at 14.150, and now try to transmit on 14.050, the K3 will automatically load the parameters stored for 14.020.  This is conjecture on my part, since I have not seen any documentation of the firmware algorithm.  But it seems reasonable and in line with what the K3 actually does.
 

Don Wilhelm-4 wrote

That is how it is supposed to work.  The "Auto" part of the tuner
function is that it remembers the tuning for 2 antennas for any band.  

[k6dgw]

I believe the KAT3 "remembers" for two antennas for each "segment" in
each band:

160: 10 KHz
80-12: 20 KHz
10: 100 KHz
6: 200 KHz

So, I ran through the bands, stopping in the middle of each of those
segments and did an ATU TUNE.  Mine now seems to know what to do without
the tuning algorithm running.  YMMV, I don't really understand all the
things I do with my K3.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org

On 5/23/2011 10:18 PM, Don Wilhelm wrote:
>    Bill,
>
> That is how it is supposed to work.  The "Auto" part of the tuner
> function is that it remembers the tuning for 2 antennas for any band.
> To get it to remember that information, one must do a TUNE on each
> antenna and on each band - after that, it is only necessary to change to
> the band and the antenna, and the tuner will change accordingly.
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[Stan Gibbs, KR7C]

Fred,

Very interesting.  It would make sense to spread the tuning segments out uniformly across the band since antenna impedance doesn't usually vary that quickly with frequency.

Thanks for the info.

k6dgw wrote

I believe the KAT3 "remembers" for two antennas for each "segment" in
each band:
160: 10 KHz
80-12: 20 KHz
10: 100 KHz
6: 200 KHz

[Matt Zilmer]

Slight correciton.  The ATU will remember ATU settings by ANT, band,
and band segment.  This allows you to get a very close tune up through
the entire band (available on all bands except 2m - K144XV), at least
for segments you've run ATU TUNE within.

Segment size in the lower bands is smaller in KHz than in the upper
bands.  Rev D9 of the owner's manual doesn't really document this
feature.  Maybe it should...

This is an excerpt from MCU 3.03 release notes, re the band segments
for the ATU:

MULTIPLE KAT3 ATU DATA SEGMENTS PER BAND/PER-ANT.: 10 kHz
per segment on 160 m; 20 kHz on 80-12 m; 50 kHz on 10 m; 200 kHz
on 6 m. This keeps narrowband antennas in tune across the full ham
band. Note 1: You do not have to go through each band and do ATU TUNE
on every segment. The K3 will use the saved LC data segment closest
to your present VFO location. Note 2: You can erase all of the stored
LC data for a given band by tapping CLR in the CONFIG:KAT3 menu entry.


73,
matt W6NIA

On Tue, 24 May 2011 01:18:06 -0400, you wrote:

>  Bill,
>
>That is how it is supposed to work.  The "Auto" part of the tuner
>function is that it remembers the tuning for 2 antennas for any band.  
>To get it to remember that information, one must do a TUNE on each
>antenna and on each band - after that, it is only necessary to change to
>the band and the antenna, and the tuner will change accordingly.
>
>The "automatic" tuner does not follow wherever you tune the VFO - you do
>have to tell it which frequencies you wish it to tune to.
>
>There are several variations on the meaning of "automatic".
>
>73,
>Don W3FPR
>
>On 5/23/2011 10:23 PM, Bill Swindell - K1LED wrote:
>> I have a K3/100 with the internal antenna tuner. The config is set to AUTO
>> but it seems that I still have to press the ATU tune button to get the ATU
>> to properly tune when I change bands. Is it supposed to be automatic or not?
>>
>>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

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[Bill Swindell - K1LED]

I appreciate all of the answers. Thanks for the help.