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

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[wayne burdick]

Leigh wrote:

> This is great! I had been meaning to ask because I have use a
> switchable BL2 ony my big loop and had no way of knowing what the KAT3
> was doing in the 1:1 and 4:1 positions, other than how long it took to
> find a match.

This is certainly one excellent use of the KAT3's LCSET mode, Leigh.

You've also given me an idea for a "BL3": Same as the BL2 but with a
relay rather than a switch for selecting 1:1 vs. 4:1. We could then use
one of the K3's spare output lines (say DIGOUT1) to switch the relay
under firmware control, per-band. There would be one wire running from
the AUX I/O connector to the BL3, and you'd need to power the relay
from the K3's switched 12 VDC accessory output.

If this is of interest, I'll ask the BL2's designer to take a look at
it. I have the same problem myself, so I already want two :)

73,
Wayne
N6KR

> On Thu, 20 Dec 2007 10:55 am, wayne burdick wrote:
>>
>> 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.
>
>

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[M0XDF]

I just bought a BL2 with my K3 - why wasn't there a BL3 then!
HiHi

I'd be interested, especially if the KAT3 worked the relay when tuning too


On 20/12/07 20:00, "wayne burdick" <[hidden email]> sent
> You've also given me an idea for a "BL3": Same as the BL2 but with a
> relay rather than a switch for selecting 1:1 vs. 4:1. We could then use
> one of the K3's spare output lines (say DIGOUT1) to switch the relay
> under firmware control, per-band. There would be one wire running from
> the AUX I/O connector to the BL3, and you'd need to power the relay
> from the K3's switched 12 VDC accessory output.
>
> If this is of interest, I'll ask the BL2's designer to take a look at
> it. I have the same problem myself, so I already want two :)
--
DonŒt complain. Nobody will understand. Or care. And certainly donŒt try
to fix the situation yourself. ItŒs dangerous. Leave it to a highly
untrained, unqualified, expendable professional.


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[wayne burdick]

I just wanted to point out that the future "BL3" (a BL2 with a 1:1/4:1
control relay instead of a switch) could also be controlled by our KRC2
band decoder. That means you could use it with any rig, not just a K3.
The KRC2 works with most analog and digital band-control outputs from
transceivers. (You can see a KRC2 at:
http://www.elecraft.com/elecraft_products_page.htm).

The KRC2 has 3 accessory outputs that can be configured using a PC
software application. So, for example, you could route the KRC2's ACC3
output to the BL3's relay control line, and select 1:1 or 4:1 mode on a
per-band basis.

The K3 already sends band information to the KRC2 on band changes, so
you wouldn't have to change or set up anything at the K3. Just
determine experimentally which Z setting at the balun is needed on each
band.

We've already got the BL3 designed  :)

73,
Wayne
N6KR


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[James C. Hall, MD-2]

It could be that the relay could be switched by sending DC voltage up
the coax, particularly if the balun is a good distance from the radio -
much like turning on a pre-amp on the mast.

73, Jamie
WB4YDL



wayne burdick wrote:

> Leigh wrote:
>
>> This is great! I had been meaning to ask because I have use a
>> switchable BL2 ony my big loop and had no way of knowing what the
>> KAT3 was doing in the 1:1 and 4:1 positions, other than how long it
>> took to find a match.
>
> This is certainly one excellent use of the KAT3's LCSET mode, Leigh.
>
> You've also given me an idea for a "BL3": Same as the BL2 but with a
> relay rather than a switch for selecting 1:1 vs. 4:1. We could then
> use one of the K3's spare output lines (say DIGOUT1) to switch the
> relay under firmware control, per-band. There would be one wire
> running from the AUX I/O connector to the BL3, and you'd need to power
> the relay from the K3's switched 12 VDC accessory output.
>
> If this is of interest, I'll ask the BL2's designer to take a look at
> it. I have the same problem myself, so I already want two :)
>
> 73,
> Wayne
> N6KR
>
>> On Thu, 20 Dec 2007 10:55 am, wayne burdick wrote:
>>>
>>> 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.
>>
>>
>
> ---
>
> http://www.elecraft.com
>
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[Thom LaCosta]

On Thu, 20 Dec 2007, wayne burdick wrote:

>
> You've also given me an idea for a "BL3": Same as the BL2 but with a relay
> rather than a switch for selecting 1:1 vs. 4:1.

And for those that bought the BL2...a handy-dandy retrofit kit.

> If this is of interest, I'll ask the BL2's designer to take a look at it. I
> have the same problem myself, so I already want two :)

Knowing that I never have the right stuff, I know as soon as you make it
available, I will find out that I've needed it all along.

Thom,EIEIO
Email, Internet, Electronic Information Officer

www.baltimorehon.com/                    Home of the Baltimore Lexicon
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[k4tmc]

David,

Not to worry...I am sure someone will develop a mod to change the BL2
to a BL3.

73,
Henry - K4TMC


-----Original Message-----
From: David Ferrington, M0XDF <[hidden email]>
To: wayne burdick <[hidden email]>
Cc: Elecraft Reflector <[hidden email]>
Sent: Thu, 20 Dec 2007 3:21 pm
Subject: Re: [Elecraft] Automatic 1:1/4:1 Balun switching under K3
control?










I just bought a BL2 with my K3 - why wasn't there a BL3 then!
HiHi

I'd be interested, especially if the KAT3 worked the relay when tuning
too


On 20/12/07 20:00, "wayne burdick" <[hidden email]> sent
> You've also given me an idea for a "BL3": Same as the BL2 but with a
> relay rather than a switch for selecting 1:1 vs. 4:1. We could then
use
> one of the K3's spare output lines (say DIGOUT1) to switch the relay
> under firmware control, per-band. There would be one wire running from
> the AUX I/O connector to the BL3, and you'd need to power the relay
> from the K3's switched 12 VDC accessory output.
>
> If this is of interest, I'll ask the BL2's designer to take a look at
> it. I have the same problem myself, so I already want two :)
--
DonŒt complain. Nobody will understand. Or care. And certainly donŒt try
to fix the situation yourself. ItŒs dangerous. Leave it to a highly
untrained, unqualified, expendable professional.


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[n6wg]

This idea is right on the money, Wayne.
I use simple dipoles with tuned feeders,
and have to manually throw the slide switch
from one band to the next. This idea would
be a real help in automating my contest
station.
Thanks and 73
Bob N6WG

----- Original Message -----
From: "wayne burdick" <[hidden email]>
To: "Leigh L Klotz, Jr." <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>
Sent: Thursday, December 20, 2007 12:00 PM
Subject: [Elecraft] Automatic 1:1/4:1 Balun switching under K3 control?

> Leigh wrote:
>
> > This is great! I had been meaning to ask because I have use a
> > switchable BL2 ony my big loop and had no way of knowing what the KAT3
> > was doing in the 1:1 and 4:1 positions, other than how long it took to
> > find a match.
>
> This is certainly one excellent use of the KAT3's LCSET mode, Leigh.
>
> You've also given me an idea for a "BL3": Same as the BL2 but with a
> relay rather than a switch for selecting 1:1 vs. 4:1. We could then use
> one of the K3's spare output lines (say DIGOUT1) to switch the relay
> under firmware control, per-band. There would be one wire running from
> the AUX I/O connector to the BL3, and you'd need to power the relay
> from the K3's switched 12 VDC accessory output.
>
> If this is of interest, I'll ask the BL2's designer to take a look at
> it. I have the same problem myself, so I already want two :)
>
> 73,
> Wayne
> N6KR
>
> > On Thu, 20 Dec 2007 10:55 am, wayne burdick wrote:
> >>
> >> 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.
> >
> >
>
> ---
>
> http://www.elecraft.com
>
> _______________________________________________
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[M0XDF]

Thanks to all for replies.
Yes, I might need to make a module anyway, because I had in mind direct use
from the K3 and not including a KRC2

73 de M0XDF / FISTS #12575, K3 # 174
Merry Xmas and a Happy New Year

On 20/12/07 21:12, "[hidden email]" <[hidden email]> sent:

> David,
>
> Not to worry...I am sure someone will develop a mod to change the BL2
> to a BL3.
--
By all means marry. If you get a good wife, you'll be happy. If you get a
bad one, you'll become a philosopher. -Socrates


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[Joe Subich, W4TV]

Wayne,

> There would be one wire running from the AUX I/O connector to
> the BL3, and you'd need to power the relay from the K3's switched
> 12 VDC accessory output.

What is the spec for the 12 VDC accessory output?  OM7ZZ ran into
some issues in interfacing with the K3 from the VP6DX group because
the accessory output was only 10.8 volts even with a well regulated
13.8V supply to the transceiver.

10.8 would be marginal depending on cable resistance for a remote
relay and is certainly too low for most of the commercial antenna
switches that use 12 V relays.  

73,

   ... Joe, W4TV

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[wayne burdick]

Joe,

We just measured the voltage at the 12V ACC output on three K3s. DC
into the K3 APP connector was 13.80 in all cases (measured at the APP
connector, K3 powered ON, in receive mode).

No load output:  13.1 VDC in all cases.

Loaded output (500mA): very close to 12.0 VDC on all three units
tested. It should be a lot higher at the typical current required for
one relay (< 100 mA).

So the total drop at maximum rated load is about 1.8 V. Circuit drops
include two series protection diodes, two self-resetting fuses, and the
PMOS FET on/off switch (Q2). These should not be bypassed or removed,
as that would compromise the safety of the ACC output.

You could replace D34 (1N4007) with a 1N5817/18/19 or SB520/530 to get
a few tenths of a volt lower drop if required. You could get another
couple of tenths by replacing both D6 and D34 with 95SQ015's, although
they're very expensive.

Sounds like OM7ZZ's output was loaded too heavily, or that he had the
radio switched off when measured it, which would provide only leakage
current. OTOH he could have tripped F2, the self-resetting fuse for the
ACC output.

73,
Wayne
N6KR

> What is the spec for the 12 VDC accessory output?  OM7ZZ ran into
> some issues in interfacing with the K3 from the VP6DX group because
> the accessory output was only 10.8 volts even with a well regulated
> 13.8V supply to the transceiver.
>
> 10.8 would be marginal depending on cable resistance for a remote
> relay and is certainly too low for most of the commercial antenna
> switches that use 12 V relays.
>
> 73,
>
>    ... Joe, W4TV
>
>
>

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[Joe Subich, W4TV]

Wayne,

> Sounds like OM7ZZ's output was loaded too heavily, or that he had the
> radio switched off when measured it, which would provide only leakage
> current. OTOH he could have tripped F2, the self-resetting fuse for the
> ACC output.

His load was a microHAM microKEYER II (setting everything for the trip).
Unit is rated at 400 mA and will indicate a fault if the input drops
below 11 volts.  

The rig and cables are on their way back to the DL group by now.

> No load output:  13.1 VDC in all cases.
>
> Loaded output (500mA): very close to 12.0 VDC on all three units
> tested. It should be a lot higher at the typical current required for
> one relay (< 100 mA).

1.5 volts +/- at 500 mA is a bit much but it's not a big problem since
MK II can use external power but it would have been nice to avoid yet
another power supply for each station for the VP6DX group.  It certainly
should not be a problem for a single relay application.

In the meantime, I'll take another look when my first K3 arrives
(whenever that is <G>).  

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: wayne burdick [mailto:[hidden email]]
> Sent: Friday, December 21, 2007 1:32 PM
> To: Joe Subich, W4TV
> Cc: 'Elecraft Reflector'
> Subject: Re: 12 VDC Output
>
>
> Joe,
>
> We just measured the voltage at the 12V ACC output on three K3s. DC
> into the K3 APP connector was 13.80 in all cases (measured at the APP
> connector, K3 powered ON, in receive mode).
>
> No load output:  13.1 VDC in all cases.
>
> Loaded output (500mA): very close to 12.0 VDC on all three units
> tested. It should be a lot higher at the typical current required for
> one relay (< 100 mA).
>
> So the total drop at maximum rated load is about 1.8 V. Circuit drops
> include two series protection diodes, two self-resetting fuses, and
> the PMOS FET on/off switch (Q2). These should not be bypassed or
> removed, as that would compromise the safety of the ACC output.
>
> You could replace D34 (1N4007) with a 1N5817/18/19 or SB520/530 to get
> a few tenths of a volt lower drop if required. You could get another
> couple of tenths by replacing both D6 and D34 with 95SQ015's,
> although they're very expensive.
>
> Sounds like OM7ZZ's output was loaded too heavily, or that he had the
> radio switched off when measured it, which would provide only leakage
> current. OTOH he could have tripped F2, the self-resetting
> fuse for the ACC output.
>
> 73,
> Wayne
> N6KR
>
> > What is the spec for the 12 VDC accessory output?  OM7ZZ ran into
> > some issues in interfacing with the K3 from the VP6DX group because
> > the accessory output was only 10.8 volts even with a well regulated
> > 13.8V supply to the transceiver.
> >
> > 10.8 would be marginal depending on cable resistance for a remote
> > relay and is certainly too low for most of the commercial antenna
> > switches that use 12 V relays.
> >
> > 73,
> >
> >    ... Joe, W4TV
> >

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[wayne burdick]

> 1.5 volts +/- at 500 mA is a bit much but it's not a big problem since
> MK II can use external power but it would have been nice to avoid yet
> another power supply for each station for the VP6DX group.  It
> certainly
> should not be a problem for a single relay application.

QSL. It wasn't meant for heavy loads.

Another thing to keep in mind is that the K3's 12 VDC accessory output
could be used simply as a switching signal, controlling a smaller relay
or a transistor that turns on the larger one. A separate 12 V supply,
battery, etc. could be used to provide switching power at the load, no
matter how distant.

73,
Wayne
N6KR


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