MY QO100 SETUP

  • and now the community is anxious waiting to see

    ur showp up on the transponder. everything seems to be well. 73 ROLF +

    Hi,

    This is a test setup. The VCO is missing and a standard oscillator is beeing used to test operation. The good news is that a 10 MHz output is available !!!

  • Yep, that's the way to go. First try to determine the gain value by putting it in hold mode and then check the difference between h1 and h65535 and do the math as described in Lars' document. This gain value is related to the Δf/ΔV ('k' of the reference oscillator).


    To check quickly if it locks, choose a short filter time constant, e.g. 16.


    Very important is to reduce noise at the ADC input. Solder the capacitor, 10M and 3k9 as close to the ADC input pin as possible. Here I soldered them ON the Arduino board. Also add an (extra) elco at the Aref pin to GND. It all helps.


  • I use a 10 uF elco from RESET to GND. This prevents the Arduino from rebooting after you connect/open a terminal session. Of course the 10 uF needs to be removed when (re)programming the Arduino (I use a jumper for this)

  • 1474 42 54564 963 Locked 14 5380 4 2 30902 909 76 0 0 0

    1475 38 54573 963 Locked -4 5380 4 2 9395 907 77 0 0 0

    1476 29 54570 958 Locked -9 5340 4 2 37607 897 78 0 0 0

    1477 37 54583 957 Locked 8 5355 4 2 16076 906 79 0 0 0

    1478 31 54585 959 Locked -6 5335 4 2 44688 902 80 0 0 0

    with homemade voltage control xtal oscilator ...

    PA3FYM I know that 50k DAC is far from 32k and diff_ns is no more than 30.

  • What I do/did:


    Take h1, let it run for a while and determine average diff_ns.

    Do the same with h65535. Take the difference between the two values, the

    gain then is 65536/difference. (suppose it's 123)


    Give in the terminal window g123 and 'r' (for run) and let it run.


    Your DAC values are somewhat high, try to get the VCO voltage so that you are somewhere in the middle (around 32000 or so). Perhaps tune it with a potmeter.


    Your filtX10 looks good (approx in the middle of the ADC range).


    The only weird thing is your timer1 value, it seems to have a lot of jitter (but that probably is due to the fact you don't have a (very) stable 25 MHz reference yet).

  • PA3FYM

    13447 9 31584 1021 Locked -12 5165 4 2 14289 935 1076 -1 65535 65535

    13448 23 31623 1023 Locked 14 5200 4 2 23670 941 1077 -1 65535 65535

    13449 13 31611 1023 Locked -10 5170 4 2 32916 933 1078 -1 65535 65535

    13450 28 31667 1023 Locked 15 5225 4 2 42336 942 1079 -1 65535 65535

    it locks also here :

    13639 18 26030 1013 Locked 14 5045 4 2 15428 931 115 0 0 0

    13640 17 26085 1016 Locked -1 5110 4 2 21471 933 116 0 0 0

    13641 5 26072 1013 Locked -12 5085 4 2 27484 927 117 0 0 0

    13642 13 26097 1022 Locked 8 5110 4 2 33601 934 118 0 0 0

    13643 -5 26043 1014 Locked -18 5035 4 2 39346 925 119 0 0 0

    and here :

    13778 -10 46935 943 Locked 1 4935 4 2 11088 877 1109 -1 65535 65535

    13779 -27 46850 935 Locked -17 4835 4 2 20492 870 1110 -1 65535 65535

    13780 -12 46860 946 Locked 15 4860 4 2 30103 877 1111 -1 65535 65535

    13781 8 46940 955 Locked 20 4970 4 2 39965 892 1112 -1 65535 65535

    13782 19 47028 965 Locked 11 5080 4 2 49286 901 1113 -1 65535 65535

    It is every 25 Hz,.Any idea ?

  • I can't figure that '25 Hz' out, but the software is written for a reference with intrinsic short term stability (like an OCXO).


    More interesting would be, if you supply this 25 MHz signal to the LNB and listen to the CW beacon. Is it stable (enough) and does it sound clear (so no crispiness/phase noise) ?

  • PA3FYM Did you try the second link as the first is CMOS out ?

    I have put the modified LNB at the roof and I was testing all 25 MHz osc to determine if some chirping is due to LNB PLL or modification but it is from the oscillator. Lars is going to be at a PCB as breidboard testing is completed. I try it with a homemade VC-XO as I did not have anything else. Have you tested also this Link ? I have build a couple of MAR8SM amplifiers with 30 dB gain and 200 mV out is not a problem I think. The main problem is phase noise and jitter at receiving as 9.75 GHz is about *5 of 1.9 GHz and as SV1IXP has told me a lot of years ago that the phase noise is the square of the ratio of frequencies. Do you have to propose a VC osc at 25 MHz for Lars?

  • Indeed phase noise goes with the square, so 20logN (where N is multiplication factor).


    I have not tried the TCVCXO in your link, but (like I mentioned several times here, and will repeat it again ; -) I use the Abracon ASVV series locked with an ADF4001 to a 10 MHz (Lars) GPSDO.


    But of course, feel free to reinvent the wheel ; -)

  • SV1BDS You mean in my case using it with a 10 MHz OCXO?


    If yes, that isn't the case here. 10 Hz up/down would be 3.9 kHz off on 10 GHz.


    My Lars has an accuracy/stability between 1E-9 and 1E-10 (after a while) and converges to tc's between 250 - 500 , which is good enough for QO-100.


  • OK, fair deal. 10 MHz Bliley OCXO's are around 12 U$ (10.50 euro) available on Ebay.

    I use such an OCXO (see picture somewhere above) in my Lars GPSDO and it works well.


    However, I think the Abracon ASVV 25 MHz VC-CXO might be a very good lead to discipline with the Lars contraption.


    ----------------------------------


    My advice (I'm not specifically talking to you):

    Some other users at this forum, asking questions for more than six months, and after that time not being able to make QSO's across the NB TPX, time is also a factor.


    There are/were early QO-100 adapters which thought about the whole frequency factory very thoroughly, based on years and years of (microwave) experience, hard work, frustration and learned it the hard way (like me).


    Trust, copy them and learn, in order to improve 'the science of QO-100' for the benefit of successors (who may improve accordingly).


    Yes, I forecast that after one week a new posting will emerge here with a question, 'invention' or 'new idea' to use a TCXO inside a PLL LNB, write their own 'discovery' on their own blogs and soon discover it doesn't work as they expected.


    Considering my forecast: I hope I am wrong ; -)