Modification of a Diavolo Twin and Octagon Twin LNB for external LO

  • If you want to have infos about modifications of Diavolo Twin and Octagon LNBs, you can find it here :

    I wrote some reports how I modified them and how to build a simple indoor TCXO.

    Everything written is in german language only. Sorry.

    best 73

    Armin DF1QE

    I still know at which end to grip the soldering iron :)

    Edited 4 times, last by DF1QE: Forum Link has changed ().

  • Hello Armin,

    Maybe you could improve your project by adding to the description that:

    - A single cable solution with ext TCXO is possible > search for OH2AUE mod (works good!)

    - As many others you don't mention the SW Drift correction in the possible stabilization methods. > SDR-Radio V3.07 (and some others)

    - See DG0OPKs HP, there he already described 2017 that the FOX TCXOs are not usable because of their digital control style. > F75D TCXO

    - A adjustable output level would be a good idea, some LNBs only lock with a much smaller ref Input level (50mVpp) > HD Line BP2


  • I also use the Diavolo-Twin-LNB. Fits nicely in the duo feed from

    For desoldering the smd XO it is not necessary to demount the pcb from the casing. Hot air station 858D+ with 470°C and fan 6 works too. I have made 2 LNB's this way without problems.

    On the signal pad of the smd XO I have used 820pF. On ground pad I have placed 50 ohms in parallel. I use a Leo Bodnar dual GPSDO with lowest singal strength at 25 MHz. The other GPSDO port feeds a pluto sdr at 40 MHz.

    The lid of the lnb casing easely cuts the red wire in the picture. This happend to me more than once. Keep the red cable away from the RT320 an its singal traces. This could cause RX interference.

    73 Harald, DL3HM

  • Many thanks for your replys and suggestions.


    Surely the hotair station is the best solution, but I wrote my report for the everage Radio-Amateur, who usually does not have those.

    I often try low-level methodes to help people with poor toolchoice.

    At an other Diavolo I tried the 2 solder iron methode as I described in one of my reports which works excellent.


    Well, some people need to make faults which others did before :-)

    Thanks for the suggestion of variable output, I will put that in my redisign which must happen anyhow with the other TCXO.

    I will have a look at the OH2AUE mod, maybe I can implement that too.

    Meanwhile I modified my 25 MHz indoor LO with a VCTCXO from Taitien.

    It's the TXEAADSRNF 25.0

    Actually I planned to use that with my next project, a GPSDO directly for 25 MHz with only one PLL (no 10MHz between), because ist's voltage controllable.

    It works fine at the measuring place, but tonight I can not test it at the LNB because right now I have the Octagon LNB in the dish. The ladder is still outside but I dont want to wake up the family :-)

    It's a pitty that the new oscillator has a bit weaker output and a bit lower DC level.

    So I had to add a C and two Rs to get the BS170 working fine.

    Well, I will let you know the fieldtest result after daylight.

    Best 73s


  • Removing the xtal:

    It is even easier if you use a so-called SMD tweezer (like TWZ100, please search the Web - about 60 EUR if you have the soldering station ). Just add some solder to both sides of the xtal, touch both sides of the xtal with the tweezer, wait a few seconds, and you can easily grab off the xtal. No need to use several soldering irons, additional tools or to remove the PCB.

    73s Oliver DL9QJ

  • Any more information about your indoor TCXO experiments Armin DF1QE ?

    73 de Frank PH2M - JO22HC

  • Hello Frank !

    At the moment not many news.

    As I already wrote, I made a new version with Conner Winfield TCXOs and they work excellent.

    Meanwhile the TCXO-Board with the golden DIL-case-TCXOs from china came in and I did a quick test. The result was not that nice. This TCXO seems to deliver much jitter. (as other hams also described) I found out that "ghost signals" appear in the receiving window. They appear every 200 kHz.

    I assume that inside this TCXOs actually a PLL is running with a loopfreqency of 512 Hz.



  • Are the Conner-Winfield TCXO's better then the Taitien VCTCXO's? I 'am a specially interested about a possible frequency range using a VCTCXO (to get possible around 25.8 MHz. for 10.489 downlink to 70M RX-IF) ?

    73 de Frank PH2M

  • O.K. Armin, all clear, I never found what the range of a VCTCXO was...

    73 de Frank PH2M