[Elecraft] Using the KPA500 with the K3 & Yaesu MKV Field

[Jack Brindle]

The short answer is that you need to disconnect the K3 from the KPA when using it with another rig.

The long answer? It would probably work the way you want if you leave the K3 powered up. That’s probably not a good idea though. The problem is that the K3 has internal pull-up resistors to VCC on the band and PTT signals. When the K3 is powered off, these continue to pull the signals to VCC, which is now zero volts. A low on the PTT input causes the KPA to go into transmit mode, which is what you are seeing. 

With either explanation, the solution is to disconnect the signals. 

By the way, it is also a good idea to disconnect the signals from the MKV when using the K3 with the KPA.

Jack Brindle, W6FB



On Nov 4, 2013, at 6:52 PM, David Inger <ingerassociates at cox.net> wrote:

> I have been using the KPA500 with my K3 with the AUX cable.  Everything has
> worked fine since Day One.  Yesterday, I hooked up a newly acquired MP MKV
> Field to the KPA with a cable from the PA Key jack on the KPA500 to the "TX
> GND" jack on the MKV.   I switch between the rigs using a coax switch into
> the amp.  Using either RF sensing or manual bandswitching,  I have no
> problems generating 500 watts with about 45 watts drive from the MKV.
> 
> 
> 
> The problem is when the MKV is in receive mode.  As long as the amp is in
> the Standby position, everything is fine.  As soon as the amp is switched to
> the Operate position, there is major attenuation of the receive signal; I
> mean like from S9 to S1.  I solved the problem by temporarily unplugging the
> AUX cable from the KPA500; receive is now normal in either the Standby or
> Operate mode.  This works but it is inconvenient.  I cannot seem to find a
> menu setting or some other means to allow by rigs to be connected to the amp
> while leaving the K3-to-KPA500 AUX cable connected.
> 
> 
> 
> Any suggestions?
> 
> 
> 
> 73 de K6SBA
> 
> David in Santa Barbara, CA
> 
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