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Ka band LNB on 24GHz?



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    UKHASnet
    Ka band LNB on 24GHz?

    Here is a Triax TKT001 19.7-20.2GHz Ka band LNB opened up...

    LO is set at 20.2GHz with DRO.

    RF Path looks promising as there is no tuning so one would tend to think that its nice and wide band ;-)
    Band pass filter is visible and probably ok to tune up so just the LO to shift to 21.8GHz if possible, we shall see.

    The 2nd/3rd LNA stage devices are marked with a D so quite possibly are the NE32584, the 1st LNA stage is marked with a J but not sure what that is!

    Here are some photos:

    LNB opened up, 2 screws and silicon to remove



    Inside 1



    Inside 2






    Modifications to get it to receive on 24GHz

    So far i have managed to get the DRO oscillator to tune up to 22.5GHz which is enough to get the IF (1.6GHz) within the passband of a regular modern satellite receiver for ATV, actually at 24.125GHz the IF will be 1.725GHz.
    Any further detuning of the LO cavity to increase the LO fails and the LO level drops off very quickly.
    To get the LO to tune up away from the original 21.2GHz I've soldered a 3mm x 1.5mm nut on the end of the LO tuning screw and shortened the coupling tracks on the LO path into the mixer diodes - see photos.

    The next step is to de-tune or possibly just remove the 20GHz band pass filter.
    Adjusting the stubs on the mixer may help bring up the mixer frequency up and also may help with higher LO frequency...


    Another Update:
    The couplers to the mixer diodes were shortened which allowed the DRO to be tuned up the band, on the end of the cavity tuning screw i fitted a M3 nut which had been filed down half way and soldered it on to the screw.

    Tests show that the LNB is very deaf at 24GHz now these mods are done (probably some 20dB down in s/n compared to Alcatel rx)... maybe the LO level is now too low to the mixer or the main lna stages are very low gain at 24GHz, still looking into it.

    to be continued sometime!










    Last page added:16/08/17 15:45
    M0DTS.co.uk