Ronnie - I sent the email quoted below to Elecraft Support on Mar 30 - have not received a reply so far-
Hi - hope all is well with the folks at Elecraft. I haven't spent much time on 10M since receiving the KPA1500 in late 2018. Recently, I was working a small opening on 10 in the FT8 mode. I noticed the noise floor on the P3 (& S meter on the K3) go up from -130 to -115 or so when the KPA1500 was switched on. The 10M ant was pointed right at the shack. I found the thread on the mail reflector from Dec 2019 (partially quoted below) & tried all the suggestions offered, etc with no relief. The noise is definitely being picked up by the antenna. With a dummy load connected to Ant1 by 3' of LMR400, the P3 level is well below -130 with the amp either on or off. I then used a "RF sniffer" set for 28.2 Mhz calibrated in dBu to check the cabling, grounds, AC input cabling, etc. The source of the noise (measured 30 dBu +) was along the DC power cable to the Amp deck from the power supply. Other cables were below 10. The power cable is factory supplied, 6 Ft long, & approaching 1/4 wave
at 28 Mhz. The serial # of my amp is 315. Any suggestions for remediation of this issue will be appreciated!
I installed a #31 mix clamp-on ferrite right at the back of the Amp deck & it dropped the noise comsiderably. When moved down to the PS case, it did not help. Seems that noise is from the Amp deck & not PS.
73 Gill W4RYW
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