ATU vs. External Tuner

[Mike Scott-7]

>Will the internal ATU work for me visiting other bands
or would I be better off installing a tuner between the rig and the
antenna?

Frank, go ahead and try the internal K3 tuner on different bands. Your 40M
dipole will work fine on 15M. I have had okay results on 30M. I am sure
losses are high but it works for the casual contacts I have made. It will
probably tune but not work well at all on 80M; at least 80M didn't work at
all for me. I have made contacts on all bands from 60M to 6M using either a
40M inverted V or a 20M dipole, don't remember which one for each band. As
Phil AD5X says coax losses will be high everywhere but 40M and 15M.

Someday I will get a real antenna but for the odd contact on another band I
seem to do okay with the internal K3 autotuner.

I would love to have a remote balanced tuner. I am building one but that is
another story.



Mike Scott - AE6WA
Tarzana, CA (DM04 / near LA)
K3-100 #508/ KX1  #1311



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[David Cutter]

I use a low doublet of 2 x 88ft straight into the K3 antenna PL via a short length of ladder line.  OK 10 - 160
David
G3UNA

>
> From: "Mike Scott" <[hidden email]>
> Date: 2008/10/27 Mon PM 01:24:25 GMT
> To: <[hidden email]>
> Subject: [Elecraft] ATU vs. External Tuner
>
>
> >Will the internal ATU work for me visiting other bands
> or would I be better off installing a tuner between the rig and the
> antenna?
>
> Frank, go ahead and try the internal K3 tuner on different bands. Your 40M
> dipole will work fine on 15M. I have had okay results on 30M. I am sure
> losses are high but it works for the casual contacts I have made. It will
> probably tune but not work well at all on 80M; at least 80M didn't work at
> all for me. I have made contacts on all bands from 60M to 6M using either a
> 40M inverted V or a 20M dipole, don't remember which one for each band. As
> Phil AD5X says coax losses will be high everywhere but 40M and 15M.
>
> Someday I will get a real antenna but for the odd contact on another band I
> seem to do okay with the internal K3 autotuner.
>
> I would love to have a remote balanced tuner. I am building one but that is
> another story.
>
>
>
> Mike Scott - AE6WA
> Tarzana, CA (DM04 / near LA)
> K3-100 #508/ KX1  #1311
>
>
>
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[John W2XS]

With a direct connection from the rig to the ladder line, there may be a balance issue on some bands.  At least that is what I saw with my antenna without a balun. I used an MFJ Balanced RF Current Meter to see this.  The SWR was always 1 to 1 so you cannot tell if there is unbalance unless you specifically measure for it.

I have recently tried a Balun Designs "Tuner" balun and it seems pretty good from a total current flow and also balance standpoint.  I put the RF Current results with the Balun Designs balun on my website (see QRZ.com for the link). I have replaced my Johnson Matchbox with the KAT3 and Balun Designs balun.

I am happy that I can use the KAT3 with its tuner settings memory for each band.  QSY is really easy now with no extra tune up needed. The balun does not seem to heat up so I assume that the loss is relatively low.

73,
John W2XS


<quote author="David Cutter">
I use a low doublet of 2 x 88ft straight into the K3 antenna PL via a short length of ladder line.  OK 10 - 160
David
G3UNA

[Jeff Wandling W7BRS]

I'm very interested in what happens when the K3's ATU is added to my
station.

My current station uses two tuners for one radio and one amplifier.

<Non K3 rig> - <300W tuner> - <SB-200> - <1.5kW tuner> - <Antenna>

The rig get's as close to 50ohm as I can manage on the little
tuner. The amp get's as close to 50ohm as I can manage on the big tuner.

(By 50ohm I mean as low an SWR as I can manage to get.. 1.1 - 1.3 typical)

It's a pain but it let's me optimize the antenna system to the point where
when I'm tuned, I get as good as I'm gonna get.  I can get 1300PEP W on
20m with the big tuner's Watt meter using 95W drive on the rig.

Now when my K3 arrives, it will have the ATU.  I'm not going to use the
wee 300W tuner for the K3.

The K3 schematic will be

<K3 w/ATU> - <SB-200> - <1.5 kW> - <Antenna>

Everything is now and will be connected via coax.

I will probably decide to use the little tuner in bypass to use it's Watt
meter to see that the interface between the SB-200 and K3 w/ATU is
revealing power output concordiant with the settings on the K3.

My antenna for all HF bands is a single dipole raised 70ft up over ground
outside.  It's cut for 40m but is tunable for 20-80m in the
aforementioned setup.

This has been working out so far, so good.  I've  neer had an automatic
tuner so I'm about to find out what happens when the ATU kicks in and
tries to work out the match.
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