Elliptical (Sky TV Type) Dish?

  • Hi Guy's,

    I have just got myself up and running on QO-100 from my home QTH using PlutoPlus, CN-0417 Pre-Amp, DX Patrol 12w Amp, Helix Antenna, 1.2m dish on TX and Bullseye LNB, Bias Tee, PlutoPlus for RX. All working very well.

    I am now looking at a very similar portable setup that I can take away with us in the Motorhome (Camping-car) over the summer months as we spend 3 months in France. The AMP is a higher power 30 amp unit and the other difference will obviously be the dish.

    Looking around on for-sale sites there are many 'portable' dishes available which from a space and weight saving perspective are ideal, even coming with their own mounting tripod. However, many of them are elliptical offset dishes rather than round offset dishes, much like the ones supplied by Sky. So my question is are these elliptical dishes worth considering both from a TX/RX signal perspective and from the point of view of mounting the LNB and Helical antenna?

    Or should I simply get a standard round steel dish and unbolt the normally fixed LNB arm when packing it all away?

    Thanks. Mark. G1INU

  • Hi Mark,
    all the components you have are necessary. For portabel acitivies I recommend an outdoor unit very closed to the dish, probably fixed at the LNB carrier, as I do. That means for transmit the Pluto as the central part, CN0417, power amplifier. For receive the LNB and the Pluto are used. Both frequencies can be handled by the Pluto, no further mixing. A network cable goes into the motor home. The receiver is locked with the SDR console. If you expect different temperatures, a stabilized external 40 MHz-clock for the Pluto gives more fun, even when it is mounted outside. Leo Bodnar is my tip. No matter what type of dish you will use. The radiation pattern of the transmit antenna should match with the f/D of the dish. Mounting of a normal LNB with a feed horn behind the reflector plate of a helix cannot be the optimum. Some friends and I use slim line LNBs with a plastic lense instead of a Horn. The wave Guide with the lense can be placed in between the Helix. Both antennas are closed to the focus point. If you like, I send pictures. Another advantage is the easy change of transmit antenna type.

  • Hi Mark,

    all looks great. Here is a picture of my "radio", mounted closed to the LNB.

    It is a good weather unit. Don't care about the plastic cup which mechanical protects the helix. It was filled with beer once.

    Your PSU seems to be a little bit oversized :).

    Before portable operation you often have to adjust the dish, I recommend to use the transponders basic noise as an indicator.

    It can be seen cearly using 2 MHz bandwith. The software is SDR# with RTL-Stick V4. The rising of the noise while optimizing the dish is independent from any signal and frequency. Behind my dish, there is a little board to carry a small laptop. Moving the tripod and the dish and seeing the maximum noise at the display takes some seconds only. Especially outside of the motor home it seems to be useful using the RTL-Stick, a little battery with a current limiter, a bias tee and a laptop, independent from the radio and the Computer inside. I call it the "setup kit".

    In the last days I made some bad experiences with heavy wind. The radio acts as like a sail. More stability is needed.

    What is about a PTT-Circuit in your setup?


  • Hi Andreas,

    Yes the PSU would be a bit overkill just for the qo-100 setup :-). I often take other commercial transceivers UHF/VHF/HF so I just take the one PSU away in the motorhome that will do any one of them.

    I like the plastic cup, is that the BeerCupFeed variant of the IceConeFeed Antenna ? :)

    On this setup I have gone for the E.Reon PowerBlast 30w amplifier from SV1AFN. It will operate with a permanent voltage of 1v to 32v to the EN pin, indeed some simply bridge across from the Vin pin. I however have added a toggle switch so I can isolate the EN pin voltage for prolonged monitoring sessions without leaving the Amp energised all the time. The toggle switch is however fed from the same 28v source as the Amp Vin pin because the EN pin voltage must not exceed the Vin Voltage. If I had fed it from one of the 5v or 12v circuits in the setup and then the 12v to 32v step up converter failed I could have ended up blowing the Amp because then the ENv would exceed the Vin.

  • Hi Mark,

    for my portabe activities I use a standard aluminium 60cm SAT-TV dish with good results.

    It is elliptical and the LNB arm slides and clicks into the dish, so it can be stored separately for transport. The antenna is mounted upside down on the tripod to get better balance.

    The second LNB is not part of the QO-100 system it is for TV reception only.

    I have a similar setup with a 40cm dish. For TX no difference, but receiving weaker SSB signals is difficult. Therefore I recommend 60cm.

    73 Armin