Hello Dave, Just checked my KX3/PX3 and with no antenna, I am also seeing spur peaks about 25 to 30 dB above the noise floor.
With the PX3 SPAN set to 30 KHz: On 20 meters, when I turn the preamp ON (20dB preamp setting), and connect my HexBeam, I only see 20m band noise at about -112 dBm; there is no sign of the spurs. If I turn the preamp OFF, then I do see some of the spurs about 5 - 8 dBm above the noise floor. To provide some idea of my actual noise floor on 20 meters, my P3 indicates -124 dBm (also with a SPAN of 30 KHz), and three other SDR radios also read -124 dBm on their respective panadapter displays, each set to a span of 30 KHz. Do you still see any of the spurs with your antenna connected on 20 meters, and the 20 dB preamp engaged? 73, Dale - WA8SRA On Sun, Jul 16, 2017 at 10:47 PM, Dave Sublette <[email protected]> wrote: > Using just one of 20 “extra” spurs, I measuredthe spur peak at -90 with > the preamp on. Base line is -125 with it on. > > Turning off the preamp, the peak is -75, base line -112. > > The s/n remains basically with preamp on and off. The main thing is, > Those spurs were not there previously. > > I just took the PX3 out to the shop and hooked it to another supply. The > spurs are still there. > > Dave > > On Jul 16, 2017, at 10:22 PM, Don Wilhelm <[email protected]> > wrote: > > > > Dave, > > > > The KX3 is designed to be operated with the preamp on most of the time. > The only reason to turn it off is when extremely strong signals are > encountered. > > > > The preamp eliminates many spurious signals that are actually out of > band due to its signal rejection "filtering". That has nothing to do with > the sensitivity, and it can kill extraneous results such as you are seeing. > > > > If it makes those responses substantial with the preamp on, then there > may be a problem to be addressed. > > > > 73, > > Don W3FPR > > > > On 7/16/2017 10:07 PM, Dave Sublette wrote: > >> Good point. However I am on 20 meters, which really doesn’t need the > preamp. Besides, the spikes are 40 dB high or so. No, this behavior is > definitely looking like a failure. I have one more thing to try. I will > carry it out to the shop in my garage and plug it in. If it is the same > there as in here, it’s not any external influence. Thanks for hanging in > there with me. > >> 73, > >> Dave > >>> On Jul 16, 2017, at 9:56 PM, Dale Boresz <[email protected]> wrote: > >>> > >>> Dave, make sure that the preamp is engaged on your KX3. If the preamp > is off and you are receiving on a quiet band, you'll see "stuff" that would > normally be covered by the band noise. Turn on the preamp, and the > artifacts that you're seeing should be pushed below the noise floor of just > about any band. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
