QO-100 setup with AMSAT-DL parts, will this work?

  • is it really necessary to operate Pluto with TCXO?

    I'm currently experimenting with unmodified Pluto and LNB as well as 70 cm dish portable setup, and I'm surprised at how stable the SDR console runs with sync on the beacon.

    Absolutely stable.

    73s de Robert

  • The idea to correct the TX by the data obtained by locking the beacons is tempting, but cannot be done:

    The RX correction (in a minimal system) corrects for the sum of LNB and Pluto instability. This cannot be disentangled. In addition, I think the Pluto does change its temperature (up) when transmitting. Not as hard as no PA is included but measureable.


    I did the TCXO change myself as well and was surprised to see little effect, but this is because I use the AMSAT-DL upconverter V1 (70cm to 13cm) due to long and tiny cables here and the resulting TX frequency drift originates now in the upconverter LO, which is currently free-running and this does heat up on TX. As the upconverter has an external 10 MHz input, I already got myself a OCXO on Ebay (15 Eur) which should get rid of the drift. This will need to stay powered 24/7 though as warming up takes some time..

  • Yes, I forgot the LNB, whose drift is also corrected in the RX line.

    So the common difference is not useful for the tx line ....


    Idea rejected ... ;)

  • Hello,


    you cannot really use the Pluto for narrowband transmission on 13cm band.


    I measured the drift of my unmodified Pluto early last year and the drift is about 10Hz per second even after one minute.

    Right after switching to TX it is even higher (25Hz/sec). Of course this might be slightly different from unit to unit but I am
    sure it is always too high.


    You can find my measurements here:


    Adalm Pluto Drift Measurements


    Kind regards


    Matthias


    http://www.dd1us.de

  • I think I might order an already TCXO modded Pluto from Ebay. Will cost more than a non-modded one, but then it is at least modded the right way. ;)

    Robert - PC5E / AC2E / SP20EJ

    Icom IC7300, Icom IC7000, Anytone D578UV, Anytone D878UV

  • Hello Robert,


    I habe modified my Pluto inject an external 40 MHz reference signal from a GPSDO. This is probably the ultimate solution but you then need a GPSDO. I am using the single unit from Leo Bodnar and I am very satisfied with it.


    Hello Achim,


    yes of course with lower frequencies the drift gets smaller ...


    Kind regards


    Matthias


    http://www.dd1us.de

  • Hello Matthias,

    I will use the Leo Bodnar single GPSDO as well. How do you connect it to the Pluto.
    Actually the most reasonable hints are:

    a) install a 18-27pF Capacitor (C124 , not used in unmodified Pluto)

    b) 3dBm SMD attenuator in the line to the Pluto (removed TCXO)


    How did you do it in practice?


    73, Oliver

  • I habe modified my Pluto inject an external 40 MHz reference signal from a GPSDO. This is probably the ultimate solution but you then need a GPSDO.

    Yes, this is the most reliable method.

    At home, everything runs synchronized with GPSDO.

    I'm just trying what minimalism portable operation is possible.


    73´s de Robert, DD4YR

  • Hello Robert,PC5E


    Why not thinking about PE1CMO? Simplex with IC-7000 on 70cm? NEVER problems for tuning uplink and downlink, you only need a 10MHZ for locking. That's all!! Most easy working setup on QO-100. Now a lot of people are still tuning around while tx-ing to their receiving part,because they just don't know how much the offset is between their rx part and receive part. It is very much annoying.

    Such a schematic looks messy due to all different part which need to be used. For some it's fun for building it all together, others like it more straight forward and easy to use. If you like some pictures, i can sent some to you. At first i was using duplex station also, but to much equipment etc was used. But of coarse, the price may be an issue. Try to make a stand-alone station, completely PC-free...it works best. That's my opinion.


    73's,Jerry

  • Jerry,


    PE1CMO is no longer selling transverters, since he ran out of parts. And duplex is the rule... While I would like a computer free setup, that can only be done with something like the Icom IC-9700... Or Pluto SDR.

    Robert - PC5E / AC2E / SP20EJ

    Icom IC7300, Icom IC7000, Anytone D578UV, Anytone D878UV

  • Ok Robert,


    To bad from CMO, but a lot of suppliers have troubles since the pandemic started.BTW,never got complaints about working simplex. Once your signal is ok, it doesn't make a difference to be on air in any way.And needing to hear yourself,hmm, that's why a lot of stations have echo's when transmitting and delayed reception at the background.I don't think you listen to your own signal too when working split on HF? I guess not.

    When using your trx's, a suggestion: dx patrol tx board+ampli with 10m IF using 7300, and for RX a simple modified lnb injected by a ref signal between 25-26MHz (if internal xtal is 25MHz) to receive directly at 439MHz on IC-7000, antenna feed could be a helix in front of the lnb(cost effective). Or Kuhne Electr if money is not a problem. For rx see Tranverterstore.com, has a G0MRF rx board directly from lnb into 2m and 739MHz(sdr-stick)


    73's, Jerry

  • BTW,never got complaints about working simplex. Once your signal is ok, it doesn't make a difference to be on air in any way.And needing to hear yourself,hmm, that's why a lot of stations have echo's when transmitting and delayed reception at the background.I don't think you listen to your own signal too when working split on HF? I guess not.

    :thumbdown:


    That's the difference between amateur satellite operation and amateur operation. On satellite's you should ALWAYS operate full duplex, Dear Jerry. See also the operating guidelines:


    Full-Duplex operation is mandatory (you must be able to monitor your own downlink while transmitting!)


    73

  • Hi Thomas,


    You are right in some way, yes, i agree to use full duplex on sats which is easier to compensate the doppler shift; you can do it also on semi-duplex, but harder to make qso's.

    But QO-100 is geo-stat sat without doppler. So i don't see any problem not hearing your own signal.I have different setups for working this sat, since i'm active from the first day, all to be used in a different way, but have 1 favorite,hi.


    73's Jerry

  • Hi Jerry, the duplex issue has been discussed in the past. Amsat-DL requires that the operator using the QO-100 satellite be able to listen to its emission and therefore to check that it is clean, that it does not exceed the beacon level, that it is on the same frequency as the correspondent. Basically these are the main reasons why duplex operations are required.

  • Hi,


    While I agree that the full duplex operation is very useful, my interpretation of the rule


    "Full-Duplex operation is mandatory (you must be able to monitor your own downlink while transmitting!)"


    is that I am able to MONITOR my signal, not necessarily permamently to listen to it.


    It would make me completely crazy if I had to listen to my own CW transmission with the delay of the satellite link and the SDR processing. So my way to comply with the rules is that I have SDR Console running and closely look at my own signal while I transmit. This allows me to see if anyone wants to interrupt me, or if my signal gets distorted in any way or my signal strength accidently rises above the beacon level.



    Vy 73


    Holger 'Geri', DK8KW

  • Surely "Full Duplex operation is mandatory" means you should operate full duplex, not simplex, not occasionally checking but always full duplex? The key words here are mandatory and must. Very strong instructive terms. Rules are what they say, not what we might like them to mean, not necessarily even what we intended to mean. You can interpret rules as much as you like but you should obey them as they are written.


    Now what might be open to interpretation is the status of these rules. If they are in guidelines they are not enforceable rules in a legal sense like say the speed limit, but nevertheless everyone is expected to follow them.


    I find hearing myself 1/3 of a second later distracting, so I operate full duplex but with reduced RX volume on TX so while I can still hear myself, it's not quite so distracting. Also an SDR waterfall to check the signal quality and level. I think this meets the guidelines.


    Mike