Posts by DD1US

  • NB Transponder Bandplan and Operating Guidelines

    Dear all,


    Geri, I assume you need to increase the bandwidth in your receiver and center the CW beacon: then you should have a steady receive level, mark and space have the same downlink level.


    The received levels from lower (CW) beacon and the (upper) experimental beacon, which transmits presently also CW, are here at my station identical (plus/minus a few tenth of dB).


    So presently both (CW) beacons can be used as level reference.


    I do not recomment to use the PSK beacon level as especially SDR console does only measure CW signal levels precisely.


    Kind regards


    Matthias


    http://www.dd1us.de



    Thus both, the lower (CW) beacon and the exper

  • Bandpass filter

    I agree with the statements above but would like to recommend to add some thoughts:


    if your filter has significant insertion loss and/or limited power capabilities it is better to place it before the final PA.


    Assume you are operating a 200W PA at 50W to keep it very linear for DATV and your filter has an insertion loss of 1dB
    then you probably do not want those additional losses attenuating your precious power ...


    Kind regards


    Matthias


    http://www.dd1us.de

  • Enlargement of the reflector on ​​a PF dish ?

    Hi Robert,


    yes, that is a bit too deep.


    However my 1.8m dish has an f/D of 0.29 and really works well in reception.


    Please also note, that the precision of the extension needs to be very precise on 10 GHz. it is not only the mesh size which need to be about 3mm max but especially the precision of the curvature.


    I had used before a mesh dish with 1.9m diameter and f/D of 0.4 and when changing to the solid dish especially the reception improved a lot.


    Kind regards


    Matthias


    http://www.dd1us.de

  • Enlargement of the reflector on ​​a PF dish ?

    Hello,
    as DH1DA has mentioned you will reduce the f/D of the dish when enlarging the diameter while keeping the focal length the same.

    This will be very beneficial especially on the receive side because the round waveguide has an opeing angle of about 130 degrees.

    In receive mode you actually want to optimize G/T and not G. The deeper dish will pickup much less ground noise.

    I am using a 1.8m PF dish with a f/D of 0.29 and even though I am underilluminating the dish I am very happy with the results.

    NB transponder noise floor is about 8dB and WB beacon MER is about 9.8dB,

    The POTY is certainly much better for dishes with a low f/D (my f/D=0.29 is clearly on the low end of the recommended range).

    Kind regards

    Matthias

    http://www.dd1us.de

  • SGLabs 13cm Transverter

    Hallo Hans,


    bei einer Stromaufnahme von nur 1A oder weniger brauchst Du bei 15m Kabellänge nicht wirklich bedenken haben. Nimm ein Kabel mir mindestens 2mm2 Kabelquerschnitt und gut ist es. Du kannst ja vor dem Transverter noch einen keramischen 10nF Kondensator und einen 1000uF Elko dranlöten. Dann kann eigentlich nichts mehr passieren.


    Viele Grüße


    Matthias


    http://www.dd1us.de

  • Abstand POTY zum Zentrum des Spiegels

    Hallo Kurt,


    insbesondere beeinflusst das f/D des Spiegels, wie genau die Brennweite getroffen werden muss,


    Bei flachen Spiegeln mit einem grossen f/D (wie die meisten sat-offset-Spiegel) ist es unkritischer,
    bei tiefen Spiegeln mit kleinem f/D (wie meinem prime-focus-dish mit f/D=0.29) ist es schon kriischer.


    Viele Grüße


    Matthias


    http://www.dd1us.de

  • Unusual station setups

    Hi Ribert,


    you are very welcome.


    Actually you can simply use the cosinus function.


    Theoretically the loss at 90 degree is infinite but in the real world it is somewhere around 20dB (because the TX and RX antennas are most likely not ideally linear polarized and you might have reflections etc.).


    Kind regards


    Matthias


    http://www.dd1us.de

  • Unusual station setups

    Hi Robert,

    interesting setup, but why did you take the route to circular polarization ?

    If you use a normal linear polarized LNB and tilt it 45 degrees then you receive also both transponders.

    Of course you will also loose 3dB on each transponder going that path.

    Kind regards

    Matthias

    http://www.dd1us.de

  • NB passband monitoring

    Hi Renaud,


    the somewhat cyclic white lines are most likely from an unknown radar source. Today it is especially bad but it has been present for quite some time.


    The pacman picture in the waterfall, which is transmitted cyclically, is to remind people to honor the guard band to the PSK beacon. ;)


    Kind regards


    Matthias


    http://www.dd1us.de

  • Montage POTY an Opticum LNB LSP-02G

    DK1MHW


    Please note that the tube acts as a high pass filter and suppresses the 2.4 Ghz signal.


    The longer the tube, the higher the suppression.


    I recommend to make it not too short but for sure not as long as shown in the pic from DD4YR above, I think 6 cm is enough.


    Also don't use regular silicone (smells like vinegar) to glue the copper to the LNB ... that will react with the copper
    and will be a mess ...


    Kind regards


    Matthias


    http://www.dd1us.de