[Elecraft] KAT500 Matching Range & Power Limits

[Dick Dievendorff]

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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