• Hello all

    I think I've found my LNB. Thanks to DB8TF and his tests I ordered an Opticum LSP-02G from Amazon but they had delivered a LSP-04H. OK I tested this one now.

    Here my results: After switch on the LNB-frequency drifts more than 10 kHz upwards. After ca. 45 minutes the frequency is "stable" between +- 1.8 kHz. I transmitted a CW-signal on 437.070.00 MHz and received the 24th harmonic on 10489.675 (middle of NB) --> AMSAT-DL-RXconverter --> Kenwood TS-711E on 144.470 MHz (+-). I heard no wobbling, see the pic:

    What do you think, have I found my unmodified LNB ?

    73 de

  • Hi Thomas,

    actually the OPTICUM LTP 04H is a good choice. It's cheap, is using the same RT320 chip as the famous Ocatagon.

    It does not have the 10 GHz Input filter, which is actually better for QO-100 ;-)

    Here some pictures from opening:

    Pictures how to modify it for the new AMSAT-DL Universal Downconverter will follow as soon as Stefan finished testing..

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

  • Yesterday and today I heard the upper PSK beacon the first time life with an unmodified Opticum LNB at an 85cm dish. It was absolutely not wobbling, the sound was clear and remembered me to the good old AO-10/13 days. :D

    But the LNB is drifting a few 10kHz down at the dish, on the table there was only about 2 kHz up & down. So I will write me a calculator software. The RX is an old Kenwood TS-711E, also from the ... (see above :))


  • DL1GNM Mike.. there are OPTICUM and OCTRAGON LNBs on the market. Thomas told about his OPTICUM..:)

    It's an Opticum LSP-04H, the model LSP-02G was also testet as wobble-free. There are also Twin-LNB's from Opticum on the market, also wobble-free. I think Opticum has the best electronic design for their LNB's, forget Octagon. ;)

  • Yes, I mixed them up. Sorry.:S

    DL1AVX: this one looks really nice. Should be easy to modify to external LO (GPSDO...).

    How about cutting the horn and would it fit to 22mm copper tube of POTY?

    73 Mike

  • That is actually done by somebody (don't know his/her call).

    When the POTY was simulated/designed (by G0MJW) we discovered that a horn seriously degrades the performance of the S-band part of the POTY (primarily gain (<-- read: illumination of the dish and somewhat axial ratio). Mike then tried another design, a round patch with 'notches'. With this design the patch surface (iirc) could be increased so that the influence of a horn was relatively less, maintaining the necessary S-band gain (<-- read opening angle = illumination of the dish).

    So there is a trade off, which is also dependent on the usage. For NB usage the degradation of the S-band part can be (more easily) compensated with increasing power and more gain/SNR with RX (with a (cut off) horn (from a LNB). However, for DATV the uplink link budget is more critical, there every 0.5 dB counts (as I have been told)

  • Remco, that's why I want always to fit a LNB to the waveguide (22/20mm copper tube). On the NB transponder I get beacon strength with 1-2 Watt key down into my 1.2m dish using POTY feed. This is working well! :thumbup:

    But it could be probably optimised a little more I've read here:

    POTY S-Band

    This would be interesting when operating in DATV using the WB transponder.

    73 Mike

  • DL1GNM Yep, I read that article with @OM6AA's comprehensive analysis of the current patch. Despite the design looks utterly simple you can see the whole thing is sensitive towards a variety of combinatorical factors (factors influencing each other, which are influencing each other, which are etc).

    The POTY was NOT designed to squeeze every pB (picobell) out of the performance but after intensive modelling deliberately as a reproducible compromise without needing (complex) metalworking equipment other than metal scissors.

  • Here a larger picture of the LNB modification for the OPTICUM LTP 04H (Twin) and the installation of the necessary 3 components to supply the LNB with the external reference through the new AMSAT-DL Down-Converter.



    In front of the blue 330nH coil you can see the small brown 120pf capacitor.

    Then at the edge the 4,7uH choke above the printed choke.

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

  • Just opened an OPTICUM LTP 04H from Reichelt like those shown in the Descripton for the new Downconverter. It looks a lot different, e.g. the Crystal is under the PCB. So no "Just open and modify it according to Amsat."X(

    Sad to hear... we have ordered 100 pieces a few weeks ago from Opticum via Amazon and they are all OK, i.e. as described... lucky we were...

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

  • My QO-100 Downconverter V3D arrived today. I assembled it and ist works (see picture).

    With the LNB, I had no success: I bought an OPTICUM LPT-04H for modification, but it has an other PCB. No quartz ...

    So my question: Where can I get the right LNB ?

    73, Martin DL9SAD