Umbrella Ultra Light and cheep dish for portable and flight baggage

  • The Umbrella DISH

    Code
    1. Greetings from the Black Forest,
    2. My idea was to develop an antenna that can also be carried in the baggage. It should be cheap too. After much research, I came across Chinese umbrellas. Advantages: light weight, stretched 80cm diameter, folded about 50cm. Parabol almost ideal for a ca.50cm focal point. With 4 watts and together with POTY patch antenna I am almost as loud as the beacon. Covered are the 22 segments with a foil from a rescue blanket. Glued to the fabric of the screen with textile glue
    3. 73 de Frank, DL2GRF
    Code
  • DL2GRF BG0AUB made hist first QSO's with his umbrella antenna a few months ago : -)

    I do not claim that I am invented the antenna. I have not seen the antenna of BG0AUB before. It´s my way to make a antenna with minimal cost and minimum light weight. I would like to show that it works. Some specialist think the surface is not smooth enough and the parabolic form is not given. how it works on receive on 10GHz I don´t know at the moment

    Frank;)

  • DL2GRF : Look here : -)

    yes thank you. I have found his umbrella. But it seems to be not optimized. The shape is too much. The prime focus is to close so you have about 180° of radiation angle. No patch feed can illuminate 180°. So only a small part should be illuminated. I think I have about 22-23dB of gain with the patch (not adjusted at this time). Compared with my grid parabolic 1-2dB less of signal

  • Inspired by this thread I did some experiments this morning.


    Now, this is what I call an umbrella dish, hi hi :):love:


    I was using a "professional" umbrella type dish. Its basically an old "portable" Inmarsat Telephone for the former Inmarsat-B service.


    I tried it with the POTY feed and constructed quickly yesterday evening a 3D printed mount for the central strut for replacing the original L-Band helix.


    I have the impression that the antenna is underilluminated with the POTY.

    (120cm diameter with F/D around 0.35)


    RX SNR was a few dB down from my usual 80cm dish and comparable to my small camping dish.


    Also the effect of my 3D printed mount on beam pattern is unclear.

    I printed with 30% infill, so I have still lots of air inside, hi)


    But due to very narrow beamwidth it is very hard to adjust and do the directional fine tuning. (my 40cm camping dish I can adjust easily within 10 seconds, hi hi)....


    Also the mesh size of the wires woven into the fabric net have a hole size of 5x5mm, which is not great for 10GHz.


    On the TX uplink I assume also due to underillumination my SNR with same power was 2-3dB lower than with my 80cm offset dish (seen in the background).


    Last but not least I also tried to optimize the focal point (I could slide the Feed forward/backward with my mount) and focal point is very critical...moving 0.5cm forward/backwards from ideal point already cost you some SNR dB.

    (again here it seems that my smaller dishes are less critical)


    So in my view, despite being nice to look at and it was fun experimenting with, I think this is not really a great antenna for real portable use. I would rather go for the typical camping-dish approach.


    73 de Oscar DJ0MY

  • Oscar, tnx for your tests and report.

    Those are somehow grounding my expectations

    and as a camping dish is available here as well...


    Probably I will give it a try anyway, but first I have to solve some issues with the Tx path in my standard QO 100 setup ;-)


    73 de Alex, DK4FT