Elecraft › [K3]

KAT3 use questions

Classic

List

Threaded

4 messages Options

Stan Gibbs, KR7C

KAT3 use questions

I just finished building a K3 (#4181) and have a question about using the
KAT3.
When I hit the ATU button with the KAT3 enabled, it does its thing for a
second or two and then flashes a SWR value on the display as expected. I
want to operate on 80m with a VERY limited choice of antennas.

My questions are:
1) If the displayed SWR is, say, 4.1:1, does that tell me that the ATU
successfully matched the load and that I can operate the radio without fear
of damage?
2) What does the display indicate when it cannot achieve a reasonable match
and I should not operate the radio?

Thanks for any info on this.

73, Stan, KR7C

______________________________________________________________
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

73, Stan - KR7C

k6dgw

Re: KAT3 use questions

Stan Gibbs wrote:

> When I hit the ATU button with the KAT3 enabled, it does its thing
> for a second or two and then flashes a SWR value on the display as
> expected. I want to operate on 80m with a VERY limited choice of
> antennas.

It shows you the "best" match it could obtain. With really mismatched
conditions, the "best match" may depend on where the tuner
was when the tuning algorithm started. If you tap ATU again, you *may*
get a better [or worse] match. Under better match conditions, this
disappears and the first tap will likely get you as good as the
L-network and algorithm can do.
>
> My questions are: 1) If the displayed SWR is, say, 4.1:1, does that
> tell me that the ATU successfully matched the load and that I can
> operate the radio without fear of damage?

The K3 will power back if it doesn't like the match. Mine won't do full
power into a 4:1 match anywhere and it complains when I try to TX.
It'll do full power into a 2.5:1 on higher bands, but not so good on 80
or 160 where I get HI SWR on occasions.

> 2) What does the display indicate when it cannot achieve a reasonable
> match and I should not operate the radio?

It tells you the SWR and then goes back to the freq display. When you
TX, you may get HI SWR, it may dial the power back, or both. Either is
an indication that you're not going to be able to transmit.

The L-Network in the ATU can match a wide range of impedances but there
are limits. If the best it can do is 4:1 SWR, you really need to do
something to the antenna. Changing the length of the coax will change
the impedance the tuner is working into and you might get a better
match, but ...

keep in mind that, if the feedpoint impedance at the antenna is wildly
mismatched to the transmission line, the SWR on the line will be very
high regardless of the length of the line, so will losses, and the ATU
may not be able to completely match it to the radio. "Antenna Tuners"
have nothing to do with the antenna. They just match the impedance seen
at the coax connector to the impedance the PA wants to see [usually 50
ohms].

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2010 Cal QSO Party 2-3 Oct 2010
- www.cqp.org
______________________________________________________________
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

drewko

Re: KAT3 use questions

In reply to this post by Stan Gibbs, KR7C

BTW, here are a couple of things you can do to achieve a better match
with the KAT3:

If you tap ATU TUNE again within a few moments after the first tune
attempt the KAT3 will go into a more comprehensive tuning mode. It
takes longer but may find a better match.

You may also be able to obtain a better match by manually setting the
tuning elements. I had that situation on 160m where the KAT3 could get
to SWR 3.5:1 but I could improve it to under 2.0 with the manual
settings (Config Menu: KAT3/LCSet).

73,
Drew
AF2Z

On Mon, 10 May 2010 14:45:10 -0600, Stan, KR7C wrote:

>I just finished building a K3 (#4181) and have a question about using the
>KAT3.
>When I hit the ATU button with the KAT3 enabled, it does its thing for a
>second or two and then flashes a SWR value on the display as expected. I
>want to operate on 80m with a VERY limited choice of antennas.
>
>My questions are:
>1) If the displayed SWR is, say, 4.1:1, does that tell me that the ATU
>successfully matched the load and that I can operate the radio without fear
>of damage?
>2) What does the display indicate when it cannot achieve a reasonable match
>and I should not operate the radio?
>
>Thanks for any info on this.
>
>73, Stan, KR7C
>

______________________________________________________________
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

David Cutter

Re: KAT3 use questions

Drew

How do you return to that manually set value without going through that procedure each time? Does it remember manual settings as well as auto-tune settings?

David
G3UNA

>

>
> You may also be able to obtain a better match by manually setting the
> tuning elements. I had that situation on 160m where the KAT3 could get
> to SWR 3.5:1 but I could improve it to under 2.0 with the manual
> settings (Config Menu: KAT3/LCSet).
>
> 73,
> Drew
> AF2Z
>
>