Posts by DJ0MY

    You have a clever son. This looks a neat solution for the SMD challenged.


    I would advise against using the tunable TCXO. The stability may be better with a non-tunable one and any frequency error can be corrected through adjusting the pluto offset setting. This setting is held in flash and retained on power cycles. Also be aware some TCXOs tuning voltage moves the frequency in discrete steps so you will find setting it exactly not to be possible for those devices.


    Mike

    Hi Mike,


    thanks for your suggestions.


    I was not aware that the Pluto could also permanently store correction settings in flash. I thought it would always rely on external software to do so. But you know - some hams like to turn knobs and not hack something into a console. hi hi:)


    The tunable version is widely in use (as it was widely propaged by Sigi DG9BFC) with no bad experience so far as compared to its fixed frequency counterpart.


    I am using it since August this year in my Pluto openly wired (see photos attached) and once tuned to the right frequency it never had to be retuned so far. Also the tuning is really smooth and sounds very analog style - therefore no discrete steps in this model noticeable as it seems...


    Oscar

    Dear friends,


    we have been busy over the past weeks designing a TCXO breakout board for the Pluto SDR.


    The purpose is mainly to support people that are afraid of soldering these tiny 1.6 x 2.0 mm sized TCXOs. With the help of this ready-made breakout board modifying a Pluto SDR should be much more accessible to the average ham.


    This project was supporting the purpose to teach my 11 year old son how to use KiCAD and getting him interested in our hobby. Most of the schematic drawing and manual PCB layout was done by him with only very little support from my side. I am very pleased about the result and the learning curve of my son. :thumbup:


    In the attached KiCAD 3D images you get an idea how the final board would look like.


    It uses the famous ABRACON ASVTX-13-C-40.000-I05-T (40 MHz, 1.8v, 0.5ppm) which is very stable when mounted away from the TRX chip, next to the FPGA. This is the VCTCXO version with frequency correction pin to set the clock to EXACTLY 40 MHz via a small SMD multi-turn potentiometer soldered onto the PCB.


    This TCXO model is "The Model of Choice" for most Pluto SDR users on QO-100, due to its superb performance for NB transponder use. You can find many references about this TCXO model on the web with many happy users. The only limitation so far was, that this modification was only suitable for SMD experts due to the extremly tiny size.



    See the attached photos of the PCB with the drawing on how this breakout board is supposed to be inserted and connected. It is just fixed at the right place with double sided scotch tape and then wired.



    We are planning to have a first batch run of professionally produced boards made in a SMD fabricating house. This means we will be able to offer this PCB ready made with all components already factory soldered as a simple kit. The board size is approximately 7x15mm with some easy to solder pads for the wire connections.



    A documentation and YouTube instruction video will be provided once first batch is available. (also including an "easy method" for removing the original XO from the Pluto)



    If you are interested to be put on our waiting list and be informed about the upcoming availability of this PCB module you can write an email to plutosdrmod@gmail.com and please indicate in how many boards you would be potentially interested. We will then add you to the mailinglist and keep you updated about our progress.



    73 de Oscar DJ0MY (and Daniel - my 11 year old desginer)

    Yesterday the special permit in Spain has expired.


    The good news is that there is a new special permit for using QO-100 uplink frequencies with effect of yesterday 26th of September 2019 and valid for one year. You can find here the new permit.


    The permit is worded to be valid for all "holders of valid amateur radio licenses".

    While not being an advocate in my personal view this wording could be interpreted that it is also valid for all foreign hams operating under CEPT license in Spain.


    The general rules were modified slightlty:

    • no mode restriction anymore to phone mode as in previous permit (this means now all modes including DATV should be legal)
    • restriction is still limiting to a maximum of 1500W ERP
    • NEW: the station must use an antenna with not less than 22.5dBi Gain


    I guess the last point is to avoid local interferences of other services, by use of a highly directive antenna.

    (I guess for circular polarisation you can remove 3dB from that value, hi hi ;))


    Permit is on a non-interference basis and in case of interference to other radio services all transmissions need to be stopped with immediate effect.


    73 de Oscar DJ0MY

    Yesterday the special permit in Spain has expired.


    The good news is that there is a new special permit for using QO-100 uplink frequencies with effect of yesterday 26th of September 2019 and valid for one year. You can find here the new permit.


    The permit is worded to be valid for all "holders of valid amateur radio licenses".

    While not being an advocate in my personal view this wording could be interpreted that it is also valid for all foreign hams operating under CEPT license in Spain.


    The general rules were modified slightlty:

    • no mode restriction anymore to phone mode as in previous permit (this means now all modes including DATV should be legal)
    • restriction is still limiting to a maximum of 1500W ERP
    • NEW: the station must use an antenna with not less than 22.5dBi Gain


    I guess the last point is to avoid local interferences of other services, by use of a highly directive antenna.

    (I guess for circular polarisation you can remove 3dB from that value, hi hi ;))


    Permit is on a non-interference basis and in case of interference to other radio services all transmissions need to be stopped with immediate effect.


    73 de Oscar DJ0MY

    Hi Ismo,


    very simple - it's just done like with most other SDR programs by mouse dragging:


    Go with the mouse over the dividing frequency scale between spectrum and waterfall and you see the mouse cursor change.

    While the mouse cursor is changed you can now hold right mouse key and drag it up/down to change size ratio of sectrum vs. waterfall.


    Enjoy.


    73 de Oscar DJ0MY

    Hallo,


    ich habe das heute auch mal getestet mit SDR Console 3.0.13 und aktuellster FW 0.31.

    Auch hier ist bei einem Singletone Signal ungefähr auf Bakenstärke eingestellt die Nebenaussendung auf 2400 MHz über den QO100 zu sehen. (allerdings bei mir viel schwächer als bei dem eingangs von DK5FA geposteten Screenshot)


    Als Gegenprobe habe ich dann mal mit SDR Angel gesendet auf der selben Frequenz und auch hier stelle ich die Aussendung auf 2400 MHz fest bei Aussendung eines Singletone Signals auf CW Bakenstärke.


    Allerdings ist davon bei SSB-Modulation und auch beim 2 Tone Test (mit SDR Console Standardeinstellugen) nichts mehr über den QO100 Transponder zu sehen. Da scheint das Signal zumindest unter das Transponderrauschen zu fallen, sofern es noch da ist.

    (leider kann ich nicht direkt auf 2.4 GHz mit Specki oder SDR messen)


    73 de Oscar DJ0MY

    Almost right - you forgot the 120pF & 330nH in series to be added to the F connector pin, too. (and from there a short wire to the PLL chip input)


    See the pictures attached to the first message in this thread.


    For the rest it seems you understood it correctly.


    73 de Oscar DJ0MY

    VERY IMPORTANT NOTE:


    Like with all HF PSK based modes it is very important for high data throughput in VARA not to overdrive your transmitter and hence create significant IMD products degrading your modulation.


    There are plenty of tutorials on the internet explaining how to setup your station for e.g. PSK31 mode by watching the ALC meter of your radio very carefully. If you apply those settings to VARA, it should be working just fine and produce clean signals.



    Find below two spectrum examples that I have taken live from QO-100:

    One OM over-driving his TX in VARA mode and creating significant sidebands and resulting bad IMD as well as unequal amplitudes of the three PSK carriers of that VARA speedlevel.


    Also as a reference see below how a clean signal looks like in comparison with more or less equal amplitudes of the three carriers and no overdriven sidebands.


    73 de Oscar DJ0MY

    I wonder if the circular waveguide (22mm Cu tube behind the mount) could be shortened without any performance issues? Shorter tube would make the total feed assemply look a bit more compact....(more for optical reasons than anything else, hi hi)


    It is randomly extended anyway by the various connected LNB types, so I guess that total length is perhaps therefore not overly critical?


    73, Oscar DJ0MY

    Inspired by this thread I did some experiments this morning.


    Now, this is what I call an umbrella dish, hi hi :):love:


    I was using a "professional" umbrella type dish. Its basically an old "portable" Inmarsat Telephone for the former Inmarsat-B service.


    I tried it with the POTY feed and constructed quickly yesterday evening a 3D printed mount for the central strut for replacing the original L-Band helix.


    I have the impression that the antenna is underilluminated with the POTY.

    (120cm diameter with F/D around 0.35)


    RX SNR was a few dB down from my usual 80cm dish and comparable to my small camping dish.


    Also the effect of my 3D printed mount on beam pattern is unclear.

    I printed with 30% infill, so I have still lots of air inside, hi)


    But due to very narrow beamwidth it is very hard to adjust and do the directional fine tuning. (my 40cm camping dish I can adjust easily within 10 seconds, hi hi)....


    Also the mesh size of the wires woven into the fabric net have a hole size of 5x5mm, which is not great for 10GHz.


    On the TX uplink I assume also due to underillumination my SNR with same power was 2-3dB lower than with my 80cm offset dish (seen in the background).


    Last but not least I also tried to optimize the focal point (I could slide the Feed forward/backward with my mount) and focal point is very critical...moving 0.5cm forward/backwards from ideal point already cost you some SNR dB.

    (again here it seems that my smaller dishes are less critical)


    So in my view, despite being nice to look at and it was fun experimenting with, I think this is not really a great antenna for real portable use. I would rather go for the typical camping-dish approach.


    73 de Oscar DJ0MY

    I am very sorry, I need to correct my earlier too optimistic results (70Hz slow drift / 30 minutes) with the TXC 7N type.


    When I did my initial tests there was no wind and overcast sky with constant outside air temperature.


    Today I did another longer term test and the LNB was in plain sunshine and it was a bit windy with varying wind speeds. I had the LNB without the outer plastic case (just metalic part) in the plain wind.


    After initial warmup the TCXO oscillated mostly up/down (this time audible) within 1-2 minutes in a range of around +/- 50Hz with sometimes some slower drift of the average center frequency of up to +/- 150Hz over longer period of time, e.g. 10-20 minutes.


    Since this setup is intended primarily for my portable station I am still OK with it.

    But my initial impression was definitively uch bettter.


    Not sure if this would improve with the outer plastic case mounted. Maybe some additional thermal isolation can't hurt. I will keep monitoring the performance.


    73 Oscar DJ0MY

    @DL1GNM: Please have a look to the earlier document from DD1US here in this thread.


    He uses it in an Octagon and instead of 27MHz he uses 26 MHz and with the resulting LO frequency he ends up around 1110 MHz IF (with a few slightly odd kHz, but that can be corrected via calibration in case of receiving with an SDR)


    This shifted LO has the advantage that it can be directly used for DATV also as that resulting IF can be directly received with a SAT-TV receiver.


    73 de Oscar DJ0MY

    Hi Roberto and all,


    yes I was still using the speed limited demo mode. Will try the licenced high speed mode later. Also ARDOP mode with 2000 lead delay later...


    In the attachements you see the Winlink status message box during the mail transfer connectng to your Winlink server.


    Also the very first testmail sent to myself.


    Great system for future emergency communications and very remote areas within the footprint of QO100


    73 de Oscar DJ0MY

    SV1BDS Yes TXC, sorry. Corrected my text above.


    I did not use voltage control. I just connected it to GND and satisfied with result.

    The feature is not well documented in the datasheet (no required voltage range given)


    73 de Oscar

    Roberto,


    my WINMORE.INI did not have those two parameters, so i added them manually.

    I am therefore not sure if they are really understood and applied by the Winmore TNC modem software.


    I tried with analog receiver (like last attempt yesterday) and with 1000 / 10 and 2000 / 10, but I hear no difference in my transmission.


    It sounds as if the break time between two connect packets is always the same default length...no matter what I set in the INI.


    One time (first try) the connection with your server suddenly happened, but then your server was sending packets to me with too short intervals and my TX was never keying PTT (maybe because the break inbetween was too short and the modem was detecting that the frequency was busy) or only after many retries from your server my TX was ocasionally keying.


    So either still the parameters are not right or the software ignores them because they are too long?


    Hmmm, not sure what else to try....


    73, Oscar DJ0MY

    Now D75F was replaced by an TXC - 7P-25.000MBP-T

    (7N types were not on stock at Digikey)


    This is the CMOS version. Just added a 10nF at the supply voltage pin against GND and a 1nF cap for coupling into one of the the PLL chip Xtal traces.


    Works like a charm and is very stable. Just had it running for the last 30 minutes on the CW beacon frequency with my Airspy SDR and had hardly around 70Hz very slow drift during that time.


    I am very satisfied now with the alternative TCXO.


    Thanks to David G0MRF for hinting us into this direction.


    73 de Oscar

    Hi Roberto,


    I will try to change the parameters in the INI and try to connect your server tonight.


    I think the delay with Winmore mode could work.


    I am not sure if ARDOP would work, because my understanding is that leader length is only the initial tone market before the synschronization starts and the data is sent?


    I think this should not have an influence on the delay between one ARQ burst and the next? (or maybe I do not fully understand the protocl, hi hi)


    Hope to have success later.


    73 de Oscar DJ0MY