USE ONE BULLSEYE FOR NB AND WB TRANSPONDER WITH A SPLITTER?


    Hi everyone,


    At the moment i have a fully operational station on the NB transponder.

    I'm using separate dishes for Uplink and Downlink.

    The Bullseye is installed on a 80 cm dish.

    I've ordered the minitiouner (fingers crossed) and I was wondering if I could use the same LNB already installed, maybe with a splitter, to feed both the the RTL-SDR (for the NB) and the minitiouner (for the WB).

    I can easily setup a dual voltage circuit (12 or 18V) to switch polarization on the LNB, so that is not an issue.


    My question is if the splitter is a viable solution, and if the answer is yes, what would be a brand\model you guys would recommend, that has a proven record of minimum insertion losses?


    Thanks


    Gio

    Hi Gio, you can safely use a TV-SAT splitter. Be careful, you need a splitter that passes the supply voltage for the LNB to only one output port. The other port must be electrically isolated to avoid possible trouble.

    Insertion loss problems do not exist in this case. In fact, the more you attenuate the conversion signal, the better the SDR works.


    Ciao Gio, puoi usare tranquillamente uno splitter per TV-SAT. Fai attenzione, ti serve uno splitter cha faccia passare la tensione di alimentazione per l'LNB su di una sola porta di uscita. L'altra porta deve essere elettricamente isolata per evitare possibil guai.

    Problemi di perdita di inserzione non esistono in questo caso. Anzi, più attenui il segnale in conversione e meglio funziona l'SDR.

    Lucio,

    thanks for the reply.


    I've just realized that the minitiouner has a built in bias tee, therefore the details you've mentioned is a key factor in choosing the right model.


    Do you happen to know any model that I could go for?

    I guess the picture you've attached is one of them, will look for it on amazon......


    thanks

    Lucio,

    thanks again.


    One last question:

    I see that the 2 ports on the splitter work on different frequencies, and the band edges are just close to the 700 MHz (more or less) of the signal to be decoded that is coming from the LNB, therefore I guess there should be a considerable attenuation right at the frequency we'll need.


    I'm sure that I'm not re-inventing the wheel here, but still wondering if this may cause some issues.

    Actually, you can't use the TV splitter modelled because it does have filters in it (it has to, because otherwise LNB noise would interfere with TV signals).


    Strange as it may sound, the one you want is:

    This is "just a TV splitter" but if you open it, it actually has a transformer inside to do the impedance thing correctly. You will see that it passes DC on all three ports, so voltage supply for the LNB "just works". Disadvantage: this splitter uses Belling-Lee connectors, though adapters to F and BNC exist.


    Note that this splitter really is different from the typical "plastic" splitter which uses resistors. Check your ohm meter.


    I would like to stress that this works for the specific use case you have. NB and WB have different polarisations, so this trick can't be used to receive NB and WB on the same single LNB. For those cases, I recommend dual LNB's, I have good experiences with the Megasat Diavolo Twin LNB, giving me two independent ports can can do each polarisation as I want for the experiment du jour.


    Geert Jan

    Geert,

    even if this was not my original intention (to be able to receive NB and WB at the same time), your suggestion was very valid.

    I've ordered a Diavolo twin LNB, I really like the fact that I can have 2 independent coax lines and run 2 receivers at the same time.


    Frequency locking on the NB should not be an issue, since I'm using SDR Console.


    On the WB, I'm not sure if the lack of an external reference to the LNB could be an issue, since I have zero experience on it, any suggestions?

    The way I see it, since the band used on DATV is much wider, small frequency variations should go un-noticed, am I right?

    I hope so :)


    thanks