[Elecraft] KAT500 Matching Range & Power Limits

[N5GE]

If you have a  KAT500, there is a good way to understand how the
tuner works in high power modes by running the KAT500 Utility while
operating the tuner and watching the Last Observed section of the
Operate tab.

The Bypass VSWR value is shown near the bottom of the Last Observed
section.  If that value is above 10.0 the tuner will fault when you
try to tune at high power. I believe there is another plateau in the
power range that causes a fault if the Bypass VSWR is above 3.0, but
I'm not sure what the power limit is for that because I only use the
KPA500 here.

Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member



On Thu, 15 Nov 2012 05:42:07 -0800, "Dick Dievendorff"
<dieven at comcast.net> wrote:

>Ed:  
>
>The KAT500 does open up the PTT line and tunes at low power.  An early step
>in that tuning measures the SWR of your 14:1 antenna with the KAT500 in its
>bypassed relay configuration.  Then the ATU finds the reactive components
>needed to match your antenna.  The "bypass VSWR" is retained in each tuner
>memory and is used to evaluate the power that the ATU can safely handle.
>Should you exceed this power, for example 1000 watts into an antenna that
>was originally 14:1, the ATU faults.
>
>I would recommend "Transmission Lines for Windows" (TLW), a computer program
>written by Dean Straw (N6BV), available in recent editions of the ARRL
>Antenna Book, to evaluate tuner component stresses at various antenna
>impedances. Our tuner configuration is what Dean calls a "Low Pass L
>network".
>
>High power high SWR results in some surprisingly high tuner voltages and
>currents. The KAT500 is robust, but the components have limits related to
>the advertised KAT500 capability.
>
>73 de Dick, K6KR
>
>
>-----Original Message-----
>From: elecraft-bounces at mailman.qth.net
>[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ed G
>Sent: Thursday, November 15, 2012 1:57 AM
>To: elecraft at mailman.qth.net
>Subject: [Elecraft] KAT500 Matching Range & Power Limits
>
>Hello,
>     I'm trying to understand what the KAT500 power limits mean in real
>life.  If I am tuning an antenna that initially shows a very high SWR (say
>14:1), and I am using high power (say 1000 watts out), the KAT500 is going
>to open up the PTT line, and the tuning operation will take place with less
>than 100 watts.  Then I will show a 1:1 SWR, and I'm ready to go with my
>1000 watts.  Operationally, what is the meaning of the 3:1 SWR limit for
>1000 watts as shown in the KAT500 specs?  Will the KAT500 fault because it
>is matching a 14:1 SWR at high power?
>--Ed--
>
>
>
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