PLUTO vs LIME: TX spectrum

  • Hi Karen

    There are some spectrum analyser shots by Ole OZ2OE for the Lime mini in this thread

    "Filtered driver amplifier for SDRs"

    Both SDRs have much better IMD products when run below maximum output.
    FYI The Pluto can produce a maximum of +3dBm at 2.4G while the Lime is around 0dBm.

    Also, I believe the Lime transmits a short pulse at 100% output while it is booting up.

    Given the difference in price, possibly the Pluto has a small advantage?

    73 David

  • I have the same question and I’m waiting what SDR gurus will say and then I will do my choice.

    I think that Lime has already connector for external Reference, if that is correct it is a plus for Lime. You can avoid the Pluto modification, I’m waiting the other have to say about that.



  • Hallo,

    I started with a LimeSDR Mini last year in early spring. At this time, the Console did'nt support Plutoboards.
    USB3.0 requires fast PCs and will in some cases not work with older hardware. USB3.0 cablelength ist limitted.

    Meanwhile things changed. The Console gives full support to Adalm Pluto. The biggest advantage is to control the Pluto via Ethernet. It can be integrated in home networks or direct coupled to a host. No limits in cablelength beside the usual Ethernet restrictions.
    With some mods, the Pluto is strongly recommended from my point of view. I found a way to send PTT-information via Ethernet. The Pluto and the amp can be placed closed to the dish.
    Many friends did this in this way and they are lucky. No matter, if there are 0 or 3 dBm Level. The following cascaded amps must be selected carefully for linear operation with Lime or Pluto.
    The actual release of SDR Console gives very comfortable use of QO-100.
    I take the chance to say again, Simon's work is highly appreciated and has my fully respect.

    Finally, the choice is clear?
    Ordering Pluto at digikey should be done together with CN0417 (Analog Devices Amp behind the Pluto)
    and a better 40 MHz TCXO (digikey number is 535-14661-1-ND).
    I did a little script in German showing much more details how to get on air with a Pluto. I f someone wants to get it, write me an email.


  • Hi David G0MRF,

    thank you for the useful link with Ole OZ2OE LimeSDRmini's measurements.

    I’m not sure that SMD 2400 MHz bandpass filter will remove spurious products near the carrier but -55 dBc level seems not bad.

    It remains to find a similar picture of the spectrum for ADALM Pluto.

    Agree - Pluto looks better - but the difference of TX power output and the price between these two radios is not significant.

    73 de Karen, ra3apw

  • Hi Alex SV8QG,

    Correct - LimeSDR mini has a dedicated U.FL connector on board for external reference.
    But taking into account that we need one more reference (25 Mhz) for LNB PLL's I usualy do it with one good reference.
    In this case make one more 40MHz reference for Pluto is not a big problem - Allan deviation will be good from OCXO and phase noise level should not be very low.

    73 de Karen, ra3apw

  • Hi Paul DD8PL,

    thank you for the link.

    I found there the next interesting explanation regarding Lime SDR mini external reference:

    LimeSDR uses an ADF4002 Phase Detector/Frequency Synthesizer to synchronise the 30.72 MHz VCTOXO to an external reference. There is a U.FL connector on the LimeSDR board used for the external reference, the supported frequency range is 20MHz to 300Mhz. Frequencies lower than 20MHz are supported as long as the slew rate is greater than 50 V/µs.

    73 de Karen, ra3apw

  • Although the Limi Mini has a connector for external reference I believe that it is necessary to move (with a soldering iron) a zero ohm surface mount resistor in order to be able to use it. I don’t feel confident doing this so use mine with the internal reference and it drifts a small but annoying amount during each over as the Lime warms up.

    73 Chris