TCXO for Pluto

  • DF5SF

    Changed the title of the thread from “TCXO Pluto” to “TCXO for Pluto”.
  • OK Uli. Thank you. Sounds like a group order could be a good idea. ?
    Has anyone tried this particular TCXO to see if it has the annoying digital jumps as part of the correction routine?
    I have had this problem so many times now and it seems to be the lower cost TCXOs that all suffer from it.

    I've tried the Fox and ECS products in the same price category and they all have the same issues.

    For my upconverter, I think I will have to go from a 3 Euro to a 10 Euro product to stop the 130Hz jumps.

    Certainly a learning process. 73 David

  • 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)

  • Hallo ...


    just a note about the plutosdr 40MHz tcxo from abracon...


    they are back in stock now after sold out in october 2019

    (after my article in Funkamteur 10/2019)...


    (but not buyed by me .. got one after this from a hamradio friend after that for my personal use)


    actual Price: 3.50€ for a single one


    https://www.mouser.de/ProductD…oHw6KB4DoXIzKXs5teA%3D%3D


    73 and happy holidays and merry christmas around

  • Maybe also helpful:



    This is a Video from OE88HSR about modifying the ADALM Pluto with a new, more accurate TCXO (Abracon 0.5ppm). Im also showing the GND-Mod to prevent random shutdowns of the Pluto with different Powerdevices.

    Special Thanks to: DL4TMA,DM4DS,DF2ET

    Homepage: http://www.oe8hsr.at
    Twitter: @MeltdownCore

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

  • Hallo Peter...


    many thanks for information...


    are there any measurement results regarding phase noise and/or iq-balance especially in digtal modes maybe datv 8psk or higer mode and please information about the correct device data and specification ... maybe datasheet and the device type?


    Many thanks


    73 de Michael dg0opk

  • ...by the way, it would indeed also be possible to feed the ADALM-Pluto with the external 40 MHz Reference from the new AMSAT-DL DownConverter. That way you have both the LNB and the Pluto perfectly stabilized... either by GPS or OCXO, depending which variant you prefer.. Indeed, the down-mixing might not be needed, but perhaps if you think about portable non-computer operation, you have a dual-use solution...

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

  • 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

  • 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

  • Looks like the easiest pluto sdr tcxo removal….is NOT removing it at all.

    According to Analog Device Pluto schematics, pin 1 of the tcxo is an Enable/Disable pin and simply grounding it should disable it.


    And this is the modification by F4DAV to inject an external reference frequency into XTALN pin through additional decoupling capacitor, and original tcxo pin 1 grounded:



    73 de Piero, IK1IYU

  • 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.

    Hi Mike,


    sorry for hijacking this old one :-)


    When you say "pluto offset setting" which is held in flash:

    Do you refer to the reference frequency command that you use via the serial terminal?

    The same commands you use when you change e.g. from 40MHz to another reference frequency?

    If so, does that have actually sufficient Hz resolution for very fine offset tuning? Or is there a seperate command for offsets?

    (I didn't come across in internet)


    I am just working on another project where it could come very handy to store a fine offset in flash.

    (rather than correcting it externally, like e.g. in SDR-Console instead).


    73, Oscar DJ0MY

  • I mean the frequency offset


    SO

    Code
    1. fw_setenv xo_correction 40000000

    For a 40 MHz reference accurate to within 1 Hz. Put your actual measurement in there. Anything outside 25ppm is ignored. If 1 Hz in 40 MHz is not enough accuracy you probably need to get out more, but you are going to have to fix it in your application.


    For a different reference clock, e.g 25MHz to use the same reference as a GPS locked LNB reference

    Code
    1. fw_setenv ad936x_ext_refclk “<250000000>“



    https://wiki.analog.com/univer…uto/devs/booting#examples