Re: Pluto:: Spurious Emissions

Simon Brown



For the time being please use SDRAngel if you want the lowest possible spurs. For the time being I’m working on a different project.


Simon Brown, G4ELI


From: <> On Behalf Of MikeC
Sent: 07 February 2022 13:38
Subject: Re: [SDR-Radio] Pluto:: Spurious Emissions



Further to my observation about the Pluto spurious, and in the light of the ongoing discussion, here is the output from the spectrum analyser. These were made at 2.2GHz but I had the same results at 144MHz. There are two taken with SDRC driving the Pluto, one at about 0dBm output and the other at -20dBm output using the tune facility. I checked in all other transmission modes, and with the mic input with the same results. The other two were taken with Pluto driven by SDRAngel at 0dBm and -20dBm. I changed the ref level of the analyser between the different levels. The Pluto was connected directly to the analyser input. The highest level spurs are at around +-1.08MHz.


The Pluto is unmodified, rev B with 0.31 firmware installed. I bought it about a year ago to use with Satsagen to give me a spectrum analyser above the 2.2GHz of my Anritsu.


These measurements are very similar to those made by Rolf DJ7TH, but obviously rather different to those made by others. I cannot reproduce the effect described by Sigi where at lower output the spurs reduce to about -60dBc. I don’t doubt what others are seeing but this is what I see. It is hard to see that this effect is an intrinsic Pluto hardware problem as with SDRAngel and Satsagen the transmission output seem clean. All a bit mysterious really.


Mike Christieson


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