Posts by DL1GNM

    I understand totally (and agree ;)). Can we put a table somewhere here? Then we can do entries then and fill it with content.


    Frequencies in GHz

    Country 1.26-1.3 2.4-2.45 5.65-5.67 5.83-5.85 10.4-10.45
    Germany 75W up/downlink only ?
    75W
    75W uplink
    donwlink 75W
    Netherlands

    ...something like that...

    etc.

    Remco, yes it's a labyrinth. Would be great, if our club (for example) could make a more detailed list that contains all of the required information for amateur satellite service as well. That was my intention.

    The DARC list contains links to PDF documents of the authorities. But those are mostly not in English or German. The document from Spain contains that a special permission is required to operate on 2400-2450 MHz. But you have to read this in Spanish language first.


    May be we can do it here in the forum?

    I expect that an improved phase noise would improve C/N of the DATV beacon. Interesting would have been to see the C/N before and after the modification.


    My modified HD-BP2 LNB did not show any changes in C/N before and after the ext. LO modification using the Leo Bodnar GPSDO as source.


    But anyway, Remco, it is an interesting idea.


    73 Mike

    I've got my SG-Labs transverter and it's working well. With 2 Watt + 1dB RG142 cable loss I'm a bit above the CW-beacon level. I use it with GPSDO.



    "Door open".


    The LNB is modified and has now an external LO (GPSDO from Leo Bodnar), see here: Twin LNB HD-BP2 with external LO.


    My GPSDO settings: 27 MHz & 10 MHz

    Link to a Triplexer.


    On 432MHz I use as exciter a FT-100 or an old analog IC402 from the 70ties (no PLL, no TCXO and drifting a bit ;)).


    My NB setup is complete so far.

    We had several discussions about this LNB. It's a TWIN and you can use it for receiving NB and WB transponder at the same time. Great for DATV with talk back then. My modification uses a triplexer indoor, feeding in DC (12V for NB transponder), 27 MHz LO (I use a GPSDO) and get an NB transponder IF out that is connected to a RTL dongle for reception.


    Summarised:

    • It uses two RDA3565ES IC sharing one 27 MHz SMD XTAL.
    • This LNB is heavily wobbling - unmodified.
    • Depending on temperature it is sometimes ok, sometimes bad.
    • There is a mutual interaction of those two outputs, if there is 0V, 13V or 18V applied.
    • These interaction results in LO drift or offset due to temperature change of power additional dissipation.
    • And not only this...
    • After cutting the horn the round waveguide can be mounted at a 22mm copper tube (POTY).
    • It is relatively easy to modify to an external LO (GPSDO or TCXO).
    • LO: 27MHz, ca. +-60mVpk at XTAL (in) measured. This is the input of an external LO.


    Modification for external 27 MHz LO:



    L1=L2=470nH wire wound (mine has < 0.8 Ohm DC)

    C1=C2=C3=100pF NP0 0805

    R1=50Ohm (or 68Ohm ...)



    Top: HD-BP2 with modification

    Bottom: without...


    Note: I did a simulation and used L, C etc with parasitics. Therefore I use 100pf.

    I you calculate f_res it's different.



    I put a foil (tesa of capton) into the cap to avoid short circuits because of the additional parts.


    I've measured at the XTAL (in) +-60mVpk. (There is a connection to PIN 20 of the RDA via a capacitor)

    So you have to put in about the same level by your LO or GPSDO.



    In my triplexer I use a poti. The level was set on best MER of the DATV beacon A71A.

    If you can't do this, try to measure the level XTAL (in) before and set the correct level.

    Or do minimum a level calculation with cable loss.


    MER is almost the same before modification.

    But frequency is now stable and exact.


    73 Mike

    I can confirm that X-tals are a source for wobbling. Since I replaced the 27 MHz X-tal in my HD-BP2 LNB by external GPSDO, the signals are stable and clear! No longer an aurora sound...


    And the HD-BP2 is known for heavy wobbling.

    I can confirm that this is a good compromise. With 2 Watt + 1m RG142 and then into my 1.2m (f/d ~0.68) offset dish using POTY I'm a bit above the CW beacon level. No need for a big PA.


    It works even in my small 60cm (55cm x60cm) offset dish with nearly the same f/d. It works even out of focus quite well. The feed holder clamp did not let me mount the POTY at the right position.


    For offset dishes like these I recommend POTY as feed.


    You did a good job, thank you.


    PS: Next challenge for POTY: one dish for ASTRA TV on 19 deg plus QO-100. I'll try this.

    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

    Yes, I mixed them up. Sorry.:S


    Peter : 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

    Indeed, those TXC 7N are an interesting alternative. Thanks for sharing information.

    Unfortunately 27 MHz is not available at digikey etc. Or have I overseen something?


    Any ideas?


    73 Mike

    DF2IC : I agree with Remco:


    "Place a PTC on the LO, or a glued PNP transistor with a resistor to GND so that it heats up the LO-chip and therefore the relative T-change is less."

    Did the same 20 ago with a 10 GHz transverter. There had been X-tal PTC-clips available, so you could pull it over the xtal in the LO. That worked quite well for CW and SSB.


    75, 55 Mike