I had a couple of other replies off list that confirmed that this is perfectly normal, and usually band noise covers these spurs up.
Apparently they are from the high efficiency switching voltage regulators on the 5V and 3.3V lines in the PX3. I suspected that, but though mine was perhaps poorly filtered or faulty, but apparently this is normal. I don't see it being a problem on HF, but could be annoying on transverter bands where band noise is much lower. Maybe once out of warranty a mod to using linear regulators could be worthwhile. 73 David Anderson GM4JJJ > On 5 Feb 2015, at 10:10, David Anderson <[email protected]> wrote: > > If you have the PX3 completely unplugged do you see those spike at 12KHz > spacing? They are very prominent then. > > Tried the following: > > REF level -145 > SCALE 80 > SPAN 50 > > Everything plugged in apart from the RX I/Q lead at the PX3 end: > > Noise floor about -138dBm > 2 spikes either side either side of centre -116dBm at 14kHz intervals. > > Now plug in the RX I/Q lead to PX3 and on 14MHz with preamp on and a dummy > load, with span at 50kHz I see noise floor rises to -130dBm, spikes now at > -112dBm but they have moved in frequency slightly away from the centre and > are space 12kHz apart. Putting Average on helps to allow the measurement, but > the spikes are obvious even with averaging off. > > They are obviously internally generated in the PX3 as they do not change as > frequency of radio is changed. > > I can't believe that it is correct that there should be such visible artefact > nearly 20dB above the noise floor. > > Any suggestions? - I did the OSB calibration procedure and that worked fine. > > I checked the cables are well seated, and have checked the tightness of the > connector nuts on the PX3. > > Before I contact Elecraft, could someone check their PX3 in the same way as I > described and let me know if they see the same effect please. > > 73 > > David Anderson GM4JJJ > >> On 5 Feb 2015, at 00:07, Phil Wheeler <[email protected]> wrote: >> >> Make sure your cables are well seated. I believe I got that symptom one time >> when one cable was not fully plugged in. >> >> 73, Phil W7OX >> >>> On 2/4/15 3:11 PM, David Anderson wrote: >>> I notice I have large spikes every 12kHz at about -115 dBm whether >>> connected to the KX3 or not. >>> Thought it may be by switching PSU I was testing with, but tried a silent >>> linear PSU with the same result. Is this normal or have I a problem with >>> the PS board in the PX3? >>> >>> 73 >>> >>> David Anderson GM4JJJ >> >> ______________________________________________________________ >> 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] > ______________________________________________________________ > 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] ______________________________________________________________ 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]
