[Elecraft] KPA500 AUX input

[Phil & Debbie Salas]

The KPA500 Band Data inputs do require the pull-up resistor mod on the K3. 
However, if your Top Ten decoder has pull-ups to 5VDC, then you should be 
able to use the Top Ten as your pull-up source as long as the Top Ten is 
turned on (if the Top Ten is off, then there will be no pull-up and the 
KPA500 won't respond to the K3 band data input without the K3 pull-up mod). 
You'll need a true DB15HD splitter cable so as to connect both in parallel. 
The only reason to diode-isolate the Top Ten is if the Top Ten loads down 
the band data output from the K3 when the Top Ten is turned off (I don't 
know if this is the case).

Phil - AD5X

"... I currently use the AUX output from the K3 to drive my 'Top Ten' type 
band decoder (actually, it's a W9XT) to drive the antenna selection relays. 
Having an early K3, the pull-up resistors are in the decoder, not the K3.

The question, should anyone venture an educated guess: Can I drive the 
KPA500's AUX input in parallel with my existing decoder using a Y cord, or 
should I isolate the K3 from both the KPA500 and W9XT with diodes?  Ralph, 
VE7XF"