Posts by DL1GNM

    I've something similar. But I put a poti in between so I can reduce the level during my transmit and rise it up when tunig in (I'm using an analog non transceive transmitter). The mute level can be set. The hardware solution was chosen because SDR Console actual is not able to mute audio if not using a limeSDR or so. (V 3.0.12). And I want to use an analog receiver in future anyway.

    OK Mike, I've tested the "good C/N MER values" in the morning. I'll try this again. What kind of dish do you use? I guess you're using a POTY feed. Would be interesting to know of which parts your receiving system consists.

    Sometimes I think my C/N correlates somehow to the signal seen on BATC WB monitor...

    Regards Mike

    A71A DATV beacon has 0.8dB lower MER (alone) compared to 5.July.2019/3.Aug.2019. Did they change uplink power or is my system degraded somehow? I got never the good MER of 8.8dB since 3.Aug. even at clear sky and empty transponder.

    I would like to know this for comparing my receiving situation with different LNBs and more...

    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 uplink
    donwlink 75W

    ...something like that...


    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.


    • 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