[Elecraft] K3 operating tip: Viewing and manually adjusting ATU L-C settings

[wayne burdick]

Most of the time you'll let the KAT3 automatic antenna tuner do its 
thing and ignore it. It has a wide matching range and saves L-C 
information per-band and per-antenna, so you'll rarely need to re-tune. 
(We do plan to add multiple stored segments per band, too.)

If you're ever curious about the actual L and C values used in the 
matching network, you can check them using a special setting of the 
KAT3 menu entry (in the CONFIG menu). Just set KAT3 to LCSET, then exit 
the menu. Next, tap "ATU TUNE". This will display the present L and C 
values.

For example, I just matched my K3 on a random wire antenna on 40 
meters, went into LCSET mode, and saw this when I tapped ATU TUNE:

    CA 0.08 nF
    L 0.25 uH

The "CA" means that the capacitance ended up on the antenna side of the 
L-network. The other possibility is "CT", or capacitance on the 
transmitter side. The capacitance is shown in nF (nanofarads) so it can 
fit into three digits on the VFO A display even when the value is over 
999 pF. The value shown, 0.08 nF, could also be expressed as 80 pF.

Now, suppose you'd like to see what the effect of changing the L and C 
values would be on the match. (Or you're troubleshooting the KAT3.) You 
can simply rotate VFO A to change the C value, and rotate VFO B to 
change the L value. Tapping "ANT" alternates between "CA" and "Ct". 
Having made a change, tap ATU TUNE again to exit the L-C display. Then 
hold TUNE to go into transmit mode and see the new SWR value.

Manual view/change of LC settings is certainly fun and educational. But 
it could also be used to give me (your overworked firmware guy) 
feedback about a difficult matching situation. I'm always open to 
fine-tuning the KAT3's algorithm. So if you discover -- using LCSET -- 
that you're able to do better than the KAT3 in auto-tune mode, just let 
me know.

73,
Wayne
N6KR

---

http://www.elecraft.com