[Elecraft] [QRO] KPA500 PIN diodes / High SWR

[Eric Swartz - WA6HHQ, Elecraft]

Hi Chuck,

We immediately protect the amp by going into bypass mode. The 
microprocessor detects the extreme SWR event and immediately routes the 
drive signal around the amp, initially though the diodes, and then 
through the bypass relay after it has switched. This happens in a few 
milliseconds.

While I do not recommend this as a normal operation test, we even have 
pulled the coax out of the dummy load at 500W during tx to test this, 
with no ill effects. (If you were at our contest university demo in 
Italy, you may know how I know this..  ;-)

We have not been able to kill the t/r diodes during lab destructive 
testing or in on-air operation.

73, Eric  WA6HHQ
----

On 4/26/2011 5:29 PM, W5UXH wrote:
> Back in Feb, Guy (K2AV) wondered in another thread:
> ------------------
> I still wonder what happens to the KPA500 pin diodes when you open with a
> dit into an unterminated coax and a 20:1 SWR.  Wayne and Co are working
> their magic into a problem that has taken most amps down.
> ------------------
>
> I would also like to know if they have been able to provide sufficient
> protection, magical though it would be.  That would be a terrific selling
> point.  I know I will eventually hit the key while in a confused state with
> the KPA500.
>
> Chuck, W5UXH