NB Transponder Bandplan and Operating Guidelines

  • Since we're now using the skirts of the transponder filter, sensitivity varies and with that the operational instructions on uplink power become more confusing.


    I'm using the Goonhilly WebSDR, assuming that it's calibration has been looked at.

    In the old days, there already was a difference between the PSK beacon (-69 dB) and the CW beacon (-72 dB)


    In the new situation, the PSK beacon is still -69dB, but the lower CW beacon is now at -76 dB, the upper CW beacon has a similar level (but I'm not sure, since the space carrier doesn't seem to switch off)


    In any case, this now gives 7dB of ambiguity as to the max uplink level ("not stronger than the beacon"). Comments?

  • pe1hzg


    Hi,


    For me the lower beacon was always the reference. The difference between the "Mark" frequency of the lower and the upper CW beacon is about 3 dB, which probably is due to the reduced sensitivity of the band at 10.490,000 MHz.


    So, until we get any other instructions, I try to keep my signal below the level of the lower CW beacon.


    But, as DB2OS mentioned in one of his posts, calibration of LEILA is not yet completed and I guess there also might still be some adjustments going on, which means we just have to wait and see how things work out.



    Best 73


    Holger 'Geri', DK8KW

  • 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

  • Hello Matthias,


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


    That is interesting what you say. I use the RSP1A at an intermediate frequency of around 1100 MHz and, independent of the selected bandwidth, the upper CW beacon is definetely 3 dB weaker here than the lower beacon. This also applies to my own signal, transmitting near the lower and near the upper edge of the transponder.


    I will check with a different set up and try to find out the reason for this.



    Best 73


    Holger 'Geri', DK8KW

  • Hi again,


    I just confirmed it with the Cornwall websdr. The lower beacon has about -77dB peak (measuring the "Mark" frequency @ 300 Hz filter width), the upper beacon -80dB.


    Not that it really matters, we still can use either beacon as a reference of course ... ;)



    Vy 73 and have a nice evening


    Holger 'Geri', DK8KW

  • I also measure 3 dB lower signal on upper beacon, but then noise floor is 2 dB lower around upper beacon, so SNR is not too different between the two.

    Furthermore with my 85 cm dish, noise floor around upper beacon is only raised 2 dB above system noise floor, which means I see both transponder noise and a large contribution from system noise. A bigger antenna may have exactly same signal/noise ratio on both beacons.


    By the way interesting how mark/space is inverted on upper beacon compared to lower. I guess this is to put space frequency on lower at exactly 10489,500 MHz and at the same time have space on upper at 10490,000 MHz?


    73 Ole OZ2OE

  • The "reference" is always the lower CW beacon, as the upper (experimental) beacon might use different modulation in future.

    As said before, leveling is not yet finished.. we are happy the new (PLUTO based) hardware is running fine..

    I assume the upper beacon level will be adjusted soon...

    73s Peter

    Peter Gülzow | DB2OS | AMSAT-DL member since 1983 | JO42VG

  • Thanks Peter! Works fine and the markers in SDR-Console were quickly adjusted to the new band plan.

    The upper beacon has still the same level and my signal varies about 1dB over the transponder and has max. lower beacon level.


    Regards Mike

  • There is no restriction on the actual mode used, but the transmitted or occupied bandwidth shall be below 2700 Hz.

    DB2OS

    Hi Peter, Most (all?) of the ADALM-PLUTO user are occupying 3 kHz of bandwidth in SSB. I don't know the ADALM-PLUTO and maybe a smaller bandwidth is not adjustable. Wouldn't the band plan have to be adjusted in this point?

    73 de Matthias

  • Hallo,

    if someone is talking about the occupied bandwith, don't forget the intermodulation distortion. This is (some times) much more than 2,8 KHz.
    Use the audio equalizer to correct the frequency response. Individual voices require adjustment. A frequency response of 6 dB per octave is recommended in the literature. Most of the signals show too much level closed to the carrier. The goal is a well balanced spectrum inside the SSB-Filter.

    Use the compression to reduce signal dynamic. Even with low signal to noise it is important to have a level control.
    Peak clipping avoids overdriving amplifiers and reduces Intermodulation.
    All this is possible with the SDR Console what I - and so much more users appreciate very much.....

    73s
    Andreas