[Elecraft] KAT100 and external watt meter question

[Glenn Maclean]

Thanks to all who replied to my watt meter question. I had numerous answers.
Thank you to all. If my understanding is correct this is what is going on.
The KAT100 automatic tuner is doing exactly what it is suppose to do. It is
making the KPA100 finals (tank circuit) happy with a 50 ohm impedance match
keeping the current and voltage in a satisfactory range. However this does
not mean the antenna is performing very well  on some bands. I was able to
see this when the watt meter was connected after the tuner and showed a very
high SWR especially on 30 meters and some of the other bands. When the watt
meter is showing a low SWR the antenna is resonant on those bands and
performing well.. On the bands  with a high SWR the tuner is absorbing a lot
of power which means the EFR (effective radiated power) at the antenna is
very poor.

Thanks again to all who replied,
Glenn WA7SPY

Orginal Message -----
From: "Tom Hammond" <n0ss@earthlink.net>
To: "Glenn Maclean" <wa7spy@attbi.com>; <elecraft@mailman.qth.net>
Sent: Thursday, January 30, 2003 2:08 PM
Subject: Re: [Elecraft] KAT100 and external watt meter question


> Glenn:
>
> >I have a question as to what is the best way to use an external watt
meter?
> >I have a DAIWA CN-101L external watt meter. I originally had the K2100 RF
> >out going to RF IN on the KAT 100 and ANT1 on the KAT100 going to
connector
> >labeled  TR  on the external watt meter and then the antenna connected to
> >the connector labeled ANT on the external watt meter. I was getting a
good
> >match according to the K2100 display and the KAT100 LED's. The external
watt
> >meter however was showing high SWR on some bands especially 30 meters. On
40
> >meters and 20 meters the external watt meter, KAT100 and K2100 SWR
displays
> >all agree. On other bands the external watt meter showed very high SWR. I
am
> >using a Carolina 40 Windom antenna by Radio works.
>
> The KAT100 _ONLY_ changes the impedance of the load it's being presented
> between its ANT1 jack and the K2!!! Even though the ATU has done its job,
> by providing an acceptable SWR to the K2, it has NOT changed the load
> impedance of the antenna or its feedline.
>
> As a result, the external wattmeter will always indicate the REAL SWR
being
> presented to the KAT100, and the KAT100 will indicate the 'TUNED' SWR
being
> presented to the K2.
>
> >I re-arranged the configuration of the watt meter by connecting the RF
out
> >from the K2100 to the TR connector on the external watt meter. Then the
ANT
> >connector on the external watt meter goes to RF in on the KAT100. Then I
> >connected the antenna to the ANT1 on the KAT100. I then went through the
> >bands. The KAT100 re-adjusted the settings on all bands. Now the external
> >watt meter shows matched power out readings compared to the K2100
display.
> >The SWR is low on all the bands according to the external watt meter,
KAT100
> >and K2100. Is this the best way to have an external watt meter connected?
>
> It all depends upon what it is you want the DIAWA meter to indicate.
>
> If you want it to duplicate the reading of the KAT100, then you have it
> configured properly right now.
>
> However, if you want to use the DIAWA to indicate actual SWR _ON_ the
> feedline going to the antenna, then you should put it on the OUTPUT of the
> KAT100, so it 'sees' what the antenna and feedline are doing.
>
> 73,
>
> Tom  N0SS
>