BaMaTech DuoBand-Feed: receive poor?

    Quote from G8KWX

    I now assume that the LSP-02G is meant for center fed dish ?

    I don't think it's for a prime, seen at the shape off the horn. Prime use more the Chaparral design.

    Anyone has an image of a seperated lnb from its Bamatech waveguide?

    It should be easy to change the lnb into another brand, but i'm not sure.I don't have a Bamatech.

    Mine is DC5GY duoband feed with modified lnb on the back off the waveguide.

    I am not surprised - where is the 10 GHz lens ? There isn't one! This feed will not work with a long focal length dish. It is a design for a deep dish only. Get a rocket style LNB, take the lens and fit it to the feed, or use one of the lens designs elsewhere on the forum.


    Is the feed at S-band really circular polarisation?


    Mike

    Quote from DL9SEC

    I can not see the real advantage using the POTY, because the 10GHz feed is very similar to that of BaMaTech.

    Maybe a solution with a standard LNB and a helix could be better for you...

    No! The POTY 10 GHz arrangement is very different. The POTY was specifically designed to use a dielectric rocket style lens right from the very start. If you don't follow the design, it won't work. It is also designed to have circular polarisation at 2.4 GHz, hence the shape. Considerable thought and a lot of EM simulation resources went into the process. The design was a compromise between performance and complexity and intended for satellite TV dishes with f/d from 0.5-0.6. It's possible to do better, but that needs more complex mechanical construction.


    A dual band helix was specifically rejected because the helix blocked the 10 GHz in an difficult to predict way and avoiding that put the phase centres quite far apart. For single band, a helix is likely to be best on 2.4 GHz and a standard LNB horn on 10 GHz.

    Quote from G0MJW

    No! The POTY 10 GHz arrangement is very different.

    Hi Mike,


    you're certainly right and yes, the S-band feed is more linear, maybe slightly elliptical.

    I meant the machanical conditions of both ("big" reflector, which limits the focus fine tuning backwards with the most LNB mounts and a "small hole" to get the waves in, instead of a wide 55mm waveguide), nothing more.


    G8KWX

    Unfortunately i cound't find that little platic bag anymore, so i can't say the order number, but there is a dielectric lens available from BaMaTech for the duoband feed with LNB for a few Euros. Jusk ask Markus from BaMaTech for that...


    73, Thorsten

    I have such selected Bamatech LNB here. It is wobbling. The wobbling effect is not very strong but it is disturbing (for me). It is usable, but all received signals are slightly hummed.


    I did not notice significant poor reception during my (very short) test with this feed (85cm offset dish Kathrein KEA 850).


    BTW: TX performance of the Bamatech feed was a litte bit better than my Winkler Helix.

    DL3DCW


    If, as you wrote, doing a short test, you will listing typically to the strongest signals, as i believe. But later on you like to receive also weaker Stations. Therefore i compare 4 different LNBs and check it for the signal strenght. You will find this under #7 to #11 in this threat. The Bamatech Duofeed will deliver the weakest Signal. I compare only the the signal strenght of the beacons in this test. As i ordered this Bamatech Duofeed i had the idea about a one dish solution, therefore i study the description of the datas carefully. There you may read, this feed is made also for offset dishes. But in this case, i follow the arguments at some places in this threat, there must be a lense delivered together with the feed to have good receiving results.




    ,


    In my first test with this Bamatech Duofeed i noted no wobbling effect, but the sensitivity is real poor.


    • Official Post

    from Information about the Duoband-Feed for Es'hail-2 from DJ7GP:


    "[...]The duoband-feed can be used in front of a primefocus dish with an f/D of 0,4 as well as in front of a TV offset mirror with an f/D of 0,6. Of course you can not expect that always the theoretically possible efficiency is reached. The 10 GHz horn, as supplied, lights a mirror with f/D of 0,4 almost optimal. By placing a dielectric concentrator (dielectric lens) on the 10 GHz horn then lights up a TV offset mirror with a f/D of 0,6 to 0,7 very well.


    Such a lense / concentrator you can buy from BaMaCom or pull out from an INVERTO LNB (Inverto IDLB-SINL24-MULTI-OPP Single LNB). [...]"

    After all the comments here. - Thanks all.- I did some experiments today.


    Best S:N on the NB beacon I achieve with normal TV lnb and my 80 cm offset dish is 38 dB which is pretty good. Focus is about 30 cm so I have a f/d of 0.4.


    With my Bamatech duo feed, if I very carefully search for and optimise the position of the feed into the focus, I can now achieve 34 dB S:N. .No dielectric lens yet.


    It seems that the position is very critical and not where my standard sat TV bracket had it. I am now going to fabricate a more optimal bracket for the duo feed.


    If I can get a dielectric lens maybe I can get a few more dB to come closer to single lnb receiver.


    All very interesting and why we do this experimental hobby.

    If the dish really is 0.4 f/d then the lens you need will be one of the very short ones. I am surprised this 80cm sky dish has such a short focal length but as it does it will be a fairly good match to a patch feed. What worries me more is there is there is such a big difference between your feed and the standard LNB. A standard LNB would be a very poor match to a 0.4 f/d dish as it would serriously under-illuminate it. You would expect the situation to improve, not get worse. Was the LNB supplied with and perhaps matched to the dish?