Posts by ra3apw

    Hello Karen

    This is not what I'm looking for, I think this are factory values. My input are about 400 mW from the up-converter's output via a short pigtail cable.

    Thanks anyway

    Hello Thomas,

    if your up-converter has 400 mW output it will be good to put 6 dB attenuator between up-converter and EP-AB003 to be in linear mode.

    Hi, thanks for the answers. My plans are to write my own Python scripts. Also to use 7470.exe as plotter emulator. At this Link it has software that can be used. My thought about Ethernet is that it will be available from any PC local or remote. Applications ideas are phase noise, alan deviation, real time web spectrum monitor of HF-UHF.

    Hi George,

    look at TimeLab from John Miles, KE5FX and

    It seems you can find most of your wishes there including Prologix GPIB (both versions GPIB-USB/GPIB-Ethernet) support

    73 de Karen, ra3apw


    I plan to buy a Prologix GPIB Ethernet adapter. Any suggestions ?


    Depends on the measuring application. I use Prologix GPIB about 5 years. I had both - NI and Prologix. Prologix works great for me with the R&S FSQ8 for measuring phase noise and with Pendulum CNT-91 for measuring Allan deviation. NI has been sold as he did no more in the applications I needed.

    73 de Karen, ra3apw

    Hi Andreas DL5CN,

    thanks for your recomendation.

    My task - to choose right SDR radio with which I can maximize the use the boards of my QO-100 transverter.

    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

    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 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

    Hello All,

    I'm between choosing ADALM Pluto and Lime SDR Mini.

    My question is: did anyone make comparative measurements of the output spectrum of these two devices on 2400 MHz with span 100 and 1000 MHz in the TX CW (FM) and SSB modes?


    Karen ra3apw

    Hi Claudio,

    Thank you for the link, I read it with interest.

    I unfortunately do not have any experience with this device.

    In my opinion, in order to make a decision about the choice of a reference signal source, first of all, you need to know two parameters:

    1. Allan deviation
    2. phase noise.

    I did not find any information on this in either the article or in the lot's description.

    Karen, ra3apw


    I don't think that Si5351 is the right choice for this SHF task. I played with Si5351 five years ago (Si5351 spectrum) and have a result of the output spectrum measurement. Si5351 is not a low noise synthesizer but a clock generator.

    Please note when a signal from Si5351 will be multiplied in LNB's PLL by 390 times the phase noise will degrade by 52 dB.

    Karen, ra3apw

    Hello Claudio IK1RQX,

    I would like to be understood correctly - I expressed my opinion and indicated the reasons for such a judgment.

    It all depends on the specific task - for example, if you want to make a frequency marker, then it is quite possible that such a solution with ICS512 will satisfy someone. Although the rubidium source provides good long-term stability but it is not the best accuracy.

    But I expressed an opinion on a concrete solution - the use of ICS512 as a reference source for LNB's 9750 MHz synthesizer - in my opinion it is necessary to look for other solutions where two conditions will be fulfilled simultaneously - good stability AND low phase noise.

    I am waiting new PCBs to check other ideas for this task.

    Karen, ra3apw

    Alex, agree, I am not sure that it's a good idea to buy this "OSC101" board.

    CTI OSC5A2B02 is a good OCXO for QO-100 station (I have the same in my QO-100 transverter).
    I measured this 10 MHz OCXO's Allan deviation and phase noise (better than -150 dBc/Hz @ 10 kHz) - no problem and stable parameters.

    IMHO, the reason of an issue is a PLL Clock Multiplier of previous generation on board. I made the similar test with NB3N502 few months ago and got PN level even 10 db worse that with ICS512.

    73 de Karen, ra3apw

    Hello All,

    FYI - some results of testing the formation of the 25 MHz reference signal for the LNB PLL and 40 MHz reference (for the VHF SDR ADALM Pluto) based on the ICS512 chip (PLL CLOCK MULTIPLIER) at Please use Google translator.

    The 10 MHz OCXO with phase noise -154 dBc / Hz @ 10 kHz acted as the main source of the reference frequency.

    As a result: 25 and 40 MHz signals are formed, stability is good but the phase noise value (-99 dBc/Hz @ 10 kHz) is not good enough.
    Use for QO-100 is not recommended.

    73 de Karen, ra3apw

    Hello Claudio,

    thank you. This is preliminary (not final) test version of PA on MW7IC2725 on FR4 (not RO4003).

    Level of 2 & 3rd harmonics are big enough (- 27 dBc for second and - 38 dBc for third) that's why additional LPF should be added on PCB.

    73 de Karen, RA3APW