"Connecting the RX directly to the antenna and the spurs are not there,.."
That seems to suggest that the signal is coupling through the T/R switch. What happens if you key the KPA500 by grounding the key line input but leave the transceiver in RX mode? (Need to be in OPER mode). Look for the * on the left side of the KPA500 LCD to confirm keying. Just to be clear - this is not a transmit test, just changing the state of the T/R switch in the KPA500. Another test - leave the RX on 10 m and cycle through the KPA500 band selections using the KPA500 band switches. Is there any change in amplitude of the spurs? 73, Andy, k3wyc ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html