[Elecraft] KAT500/KPA500 - Sanity Check Please

[Dick Dievendorff]

Bypass SWR is the SWR of the antenna, measured with the ATU bypassed.

The ATU does interrupt the amp key line when the bypass SWR is too high AND there is enough forward power to endanger ATU components. It’s a fault.

At 3:1 bypass SWR the ATU can handle a kilowatt. 

At 10:1 bypass SWR the ATU can handle the full output of a KPA500, but not 1000 watts.

Some antennas higher than 10:1 SWR can be matched.  But RF forward power needs to be reduced a bit. 

But some amazingly poor antennas can do the job if that’s all you have available. The ATU shouldn’t stop you from using a bad antenna until the combination of power level and high bypass SWR endanger ATU components.

There is another “amp key interrupt” SWR threshold to protect the amp; that’s the SWR as seen by the amp, with ATU matching.

73 de Dick, K6KR

> On Jan 26, 2019, at 10:17, Andy Durbin <a.durbin at msn.com> wrote:
> 
> "Should the key line cables from the KAT500 to the KPA500 and the rig (using a Flex) prevent keying the amp if the SWR exceeds 10:1 automatically?"
> 
> I'd suggest installing and running the KAT500 Utility.   It will give a clear indication of whether the KAT500 is inhibiting the KPA500 key line (Operate tab, others, Amp Key Interrupt) .   To the best of my recollection Bypass VSWR is never used to interrupt the keying line.  However, if you are  bypassed, and transmitting with excessive VSWR, then the key line will be interrupted because of the current VSWR.   VSWR thresholds can be set with KAT500 Utility, Configuration tab, VSWR thesholds.
> 
> Andy, k3wyc
> 
> 
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