Pluto SDR, help needed - Page 1
Forum section: electronics / rf-microwave

author: barrds
author_rank: Contributor
timestamp: August 04, 2023, 08:06:15 am
content: Just received one (revision C) from Digikey and I think the Output Power is too low.Software: SDRangel (TX att. at 0 dB)1. with a 1 GHz Spectrum Analyzer- 325 MHz: -18 dBm- 432 MHz: -15 dBm- 800 MHz: -11 dBm2. Boonton 8 GHz power meter (broadband measurement)- 325 MHz: -4.3 dBm- 432 MHz: -3.0 dBm- 800 MHz: -3.0 dBm- 2.4 GHz: - 0.9 dBm- 6 GHz: -4.0 dBmChecked with SATSAGEN software and the meas. are basically the same.Could someone do me a favor a check these values in a Pluto SDR??Many thanks in advance

author: 3apw
author_rank: Contributor
timestamp: August 04, 2023, 10:53:33 am
content: TX power on 2.4 GHz from PLUTO rev.C should be about 0 dBm (I use this rig for QO-100 sat with SDR Console software).Measured about 10 x PLUTO SDR by R&S FSQ8 (SA) and Anritsu ML2437A / MA2472A (power meter).Please check the setting - TX Power level (max) and mode (NFM).

author: barrds
author_rank: Contributor
timestamp: August 04, 2023, 12:16:59 pm
content: Was that measurement of 0 dBm at 2.4 GHz made with the SA or the power meter, as the last one is a broadband meas. that include all the harmonics ?Checked with SDR Console at 100% TX Drive too: almost the same results on the measurements made with the SA, but the power meter meas. are even 3.7 dB lower.

author: 3apw
author_rank: Contributor
timestamp: August 04, 2023, 01:02:35 pm
content: Both (SA & power meter) provided the same level about 0 dBm for 2400 MHz carrier .Level of harmonics is not big enough to change a level between SA and wide band power meter.Checked with original ADALM PLUTO (from Analog Devices) and few clones PLUTO PLUS from China (which works better).FYI - Matthias, DD1US made a note about PLUTO TX power on 2400 MHz - please find the attachment.

author: barrds
author_rank: Contributor
timestamp: August 04, 2023, 03:48:15 pm
content: I'll check out the attachment.Many thanks for your help !

author: mertipolati
author_rank: Newbie
timestamp: May 02, 2025, 04:58:48 am
content: Could you fix the power issue? If so, how? I'm currently having a similar problem with my Pluto too.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 03, 2025, 01:39:03 pm
content: Beware that Pluto generates a square wave, and there are no output filters (at least that was the case in the first Pluto version, the one I have, don't know if later they added filters).So, if you generate a CW and look only at the central frequency (with a narrow bandwidth), a lot of energy will be spread into all the odd harmonics a square wave has. My guess is the dB specs are derived from the max DAC output voltage, but the output is a square wave with a broad spectrum, not a sinusoid where all the power goes into a single spectral line.

author: MRF237
author_rank: Contributor
timestamp: May 28, 2025, 04:34:43 pm
content: QuoteWhen testing with gnu radio, I found that the input range of the Pluto sink is +/- 16, instead of the expected +/- 1.Therefore, adding a constant multiplier (x16, i.e., shift 4 bits) gives the maximum output.N.B.: This issue is fixed in the latest version of gnu radio.

author: radiolistener
author_rank: Super Contributor
timestamp: May 28, 2025, 05:12:01 pm
content: Quote from: MRF237 on May 28, 2025, 04:34:43 pmbe careful because such bit shifting multiplication add noise and can add bias, which is not good when you want to listen for weak stations.