Posts by HB9VEQ


    I'm having issues receiving DATV signals from WB transponder.

    My current set-up is:

    85cm dish

    Opticum LSP-02G LNB (-> supply voltage is 18.5V)
    Adalm Pluto and/or RTL SDR USB Stick

    I tired with SDR Angel and with this software. But the video and audio is mostly not stable...

    I played with the BB gain setting and the current setting gives me the best result.

    Is there anything else I could optimize in the settings to get a better signal?

    On NB transponder my SNR is 31 dB (CW beacon) - is that enough for receiving DATV signals via WB?

    Thanks + 73


    Very helpful people here! Again, thank you very much for the detailed explanations.

    I have less experience in electronics, so I trusted the information from manufacturer (too much) and didn't question it.

    It 'sme again.

    I did the math but I'm still confused.

    Because as I said in one of my last post I can not understand why there are two values (dBm / CMOS voltage).

    If I take the dBm value and calculate the corresponding voltage I could not get close to the 3.3V CMOS.

    square wave +13.3dBm @ 50 Ohms =

    21.38 mW, 1.034 Vrms (2.068V p-p), 20.68mA

    Help - where's the error in my logic?

    Thanks in advance!

    I'm still struggling with this…

    I'm a bit confused about the output voltage of the GPSDO because the homepage states the following:

    Both output signals square wave at 3.3V CMOS levels with 50 Ohms characteristic impedance.

    Output power level (measured at 10MHz, fundamental power channel):

    +13.3dBm, drive setting 32mA

    +12.7dBm, drive setting 24mA

    +11.4dBm, drive setting 16mA

    +7.7dBm, drive setting 8mA

    From my point of view these values are contradictory because CMOS voltage != dBm related voltage:

    7.7dBm at 50 Ohms = 1.535V p-p

    13.3dBm at 50 Ohms = 2.924V p-p

    I can also measure with a oscilloscope an output voltage of ~3.3V p-p (no matter which drive setting).

    Where is my mistake?

    Uh - 1.3 V p-p

    I wasn't aware about the input limits of Pluto's SDR chip. Thank you for highlighting this!

    According to the GPSDO specifications the output signal is a square wave at 3.3 V CMOS level. Due to the lack of a proper oscilloscope I can only measure up to 20 MHz. Up to 15 MHz I can measure an output level of 3.3 V p-p (without load).

    So 3.3 V p-p is obviously way too much.

    Maybe a simple voltage divider is a good solution to protect the Pluto from getting fried?

    DJ0MY: I really appreciate your feedback. I'm wondering why my Pluto is still alive because of the high clock input. I have also set the GPSDO drive to the lowest level (8 mA).

    Hopefully someone has still the measured results and can post them here.

    Hi all,

    I'm using a Adalm Pluto with an external GPSDO from Leo Bodnar (40 MHz / 8mA drive) . Everything works quite good.

    Today I had a QSO with an OM via QO-100 who told me that I should not connect the GPSDO directlyto the Pluto because the SDR chip might get fried. After the QSO I was a bit scarred and therefore I searched in this forum for more information. But I could not find any recommendation to add an attenuator between the GSPDO and the Pluto.

    Sorry - maybe a strupid question:

    Is it really true that my setup might damage my Pluto?


    73 Mic

    Pluto with to low LO..

    Hi Michael,

    as mentioned in my previous post, we are also discussing this topic in another thread in the German part of the forum.

    We are wondering if other users are also facing similar issues with the Pluto.

    You suggested that the issue might be related to a low LO level. So now I'm curious if this is a guess or do you already have some kind of practical experience with the issues?

    Thanks for any kind of feedback.

    73 Mic

    HI all,

    I have (maybe) a strupid question regarding the DJ7GP-Feed:

    I checked the DC resistance of the 2.4GHz Patch and the meter shows 1.1 Ohms. So now I wonder if the antenna works like a folded dipole which forms a closed loop?


    73 Mic