BaMaTech DuoBand-Feed: receive poor?

  • Than you need to remove the lense, otherwise you under-illuminate your dish...


    According to the BamaTech description: "The 10 GHz horn, as supplied, lights a mirror with f/D of 0,4 almost optimal."

    Peter Gülzow | DB2OS | AMSAT-DL member since 1983 | JO42VG

  • The 'Bamatech Horn' is actually an 'open' waveguide, so suitable for f/D's up to 0.45. When having a f/D > 0.45 the waveguide needs 'some focussing' to illuminate the dish so that the -10 dB points of the lobe coincide with the (horizontal) edges of the (offset) dish. Either a horn or dielectric lens may be a solution. (such as developed and deployed in zillions of broadcast LNB's ; -)

  • DD0KP


    Hi Heiner, i believe i have been very clever and buy a Venton EXL-T Rocket Twin LNB, the only problem is this type don´t fitt to the Bamatech Duo Feed. Also i still wait for the lense of Bamatech itself. Have ordered and paid about 14 Days ago. If this parts arrived here i like to compare the Bamatech Duo Fed against the GM 201 wich produce a very good signal, but the Bamatech doing realy poor until now.

    If you get lenses from Venton wich fitts to the Bamatech i´m interested to buy one from you.


    73 Joachim

  • I used a lens from an Inverto Rocket LNB it fit perfekt on the BaMaTech Patchfeed. When I compared the lenses on my, now used, Potty Feed the Venton was a bit better than the Inverto one but as it fit so perfekt I let it on the BaMaTech. See Picture below. I have the first version on the BaMaTech with SMA plug for the 10GHz, attached is modified GM201.


  • Die Original Bamatech Linse für den Duo Feed ist jetzt eingetroffen.



    Ansicht auf die Innenseite



    Die Linse von dem nicht passenden Venton EXL-T Rocket Twin LNB habe ich wieder mit dem LNB zusammengefügt.


    Als nächstes werde ich die Original Linse auf das Duo Feed aufsetzen und danach eine erneute Messung durchführen.

    Den Vergleich Duo Feed ohne und mit Linse werde ich hier dokumentieren. Ohne Linse war der Empfang am 85 CM Offset Spiegel nicht brauchbar.


    Den im Verhältnis teuren Venton EXL-T Rocket Twin LNB werde ich auch testen und das Ergebnis hier mit einfügen.

  • Like to use for receive and transmit a offset TV antenna. Read several articles about a feed for receiving and transmitting via this single dish. Read carefully the description from Bamatech, ( #28 above) I made the decision to use the Bamatech Duoband feed LNB. Install the Duoband feed to the dish and carried out the first measurement.


    The result has been frustrating to me, realy poor signals. After that i have to learn, a lense will be neccessary for a better result. Ok, i order a Vento EXL - T Rocket Twin LNB remove the lense, but this lense don´t fitt. Ordered the original lense from Bamatech and this fitt mechanical perfect to the feed. Made a first test with this lense.


    Looks better, but not realy good. Connect the transmit cable and carry out first QSOs with this combination. The received signals don´t come out of the noiselevel and i have not been happy with the result. On the other hand my transmit signal with this duofeed is quit ok.

    So for some QSOs i use the websdr from Goonhilly for it. Finally a install again the GM 201 LNB and compare the result with the Bamatech feed.

    This signal level is quit ok and i´m happy with that but for transmitting i have to find out a solution. One possibility is to use a second dish and fitt for transmitting the Duofeed there. I study more lecture about the problem anf found a solution here:

    https://rfantennas.wordpress.com/ this shows what will be neccessary to fitt the Duo feed in the correct position for a offset dish.

    You must cut the feedarm and contruct a new feedholder, which is movable in Z and X axis to get maximal signalstrenght.

    So if you like to use the Bamatech Duoband Feed for a offset dish you must carefully study this and other articles. Also in the Bamatech description (see #28) there should be a footnote placed about this problems. Allready in (#32) i ask who has fitt a Bamatech Duofeed in the normal feed of a offset dish and is 100% happy with it. Together with the lense Bamatech send me the followig drawing.



    Also for this picture there should be a footnote

    This lense looks different to the lense i received from Bamatech


    What i will do further to overcome my problem? From the AO 40 time i still have a Winkler parabol dish 60 CM.

    Will fit the Duofeed there and find out how is the result in this configuration. In a dish like this, it is only neccessary to move the direction of the feed in one level to find the maximum signal strenght. The results i will later present here.


    73 Joachim

  • i ask who has fitt a Bamatech Duofeed in the normal feed of a offset dish and is 100% happy with it.


    I use the Bamatech Feed (including LNB) on my portable setup for it's small mechanical footprint.

    It is about 2dB down on both tx and rx compared to my well-optimized POTY that I've been using and optimizing for a year at home.


    Trying different lenses (or no lens at all) does make an impact, but not in the order of magnitude that you are observing, so there must be something fishy.


    73, Michael

  • DH5DAX


    i´m interested in a screenshot from your sdr console as well a picture from the feed in your antenna. I have ordered and just received a Triax dish 85 cm. Will try it with this dish, i believe my other dish don´t allow to come rigth into the focuspoint. Maby still my LNB is bad, on the other hand the Bamatech produce a quite good transmit signal.


    73,Joachim

  • I can provide a picture of the feed mounted to the dish, no problem.


    Providing a picture of SDR Console with the feed is something that I'm not willing to do right now as it is cold and raining over here (it's my portable setup) so you'll have to trust me that it's only about 2dB down. I see an SNR of 40dB on the CW beacon with my POTY and 38dB with the Bamatech Feed+LNB.

  • DH5DAX




    Sieht gut aus deine portable Antenne. Was ist das für eine Abdeckung für das Bamatech Feed? Ist das Bamatech Feed die Version mit dem LNB gleich dabei? Bei mir ist das auch die Version mit LNB. Da das Senden mit diesem Feed normal aussieht könnte mein Problem auch an dem LNB selbst liegen. Wenn ich es im Triax Spiegel erprobt habe werde ich die Werte hier ablegen.


    Hier mal einige Bilder einer portable Anlage für einen geostationären Satellten welche ich vor ca. 30 Jahren für den Präsidenten der Vereinigten Arabischen Emirate VAR in Abu Dhabi in Betrieb genommen habe.



    PA und LNA waren direkt an der Rückseite der Antenne angebracht. Uplink 1,6 GHz Downlink 1,5 GHz System Inmarsat



    Die Antennen sind aus einem Carbon Material gefertigt. Die vier Teile sind im Deckel verstaut und werden zum Betrieb durch eine Klickvorrichtung zusammen gehalten.




    Programmiert habe ich die Geräte dann unter freiem Himmel, ID Nr. etc. Auch das Deutsche Auswärtige Amt hat diese Geräte auf den Botschaften eingesetzt. Im Amsat Journal 1/2019 habe ich dazu etwas geschrieben.




  • Hallo Joachim,

    Sieht gut aus deine portable Antenne. Was ist das für eine Abdeckung für das Bamatech Feed? Ist das Bamatech Feed die Version mit dem LNB gleich dabei? Bei mir ist das auch die Version mit LNB. Da das Senden mit diesem Feed normal aussieht könnte mein Problem auch an dem LNB selbst liegen.


    die Abdeckung ist eine Frischhaltedose aus dem Supermarkt, ich habe in den Deckel ein kreisrundes Loch geschnitten, Die Originaldichtung ist zusammen mit dem Reflektor zu dick, also habe ich sie weggelassen. Das ist so zwar nicht mehr ganz wasserdicht, aber erfüllt dennoch seinen Zweck ganz gut, es können sich keine Regentropfen zwischen Patch und Reflektor sammeln.


    Ja, in die Richtung geht meine Vermutung auch, so stark aus dem Fokus kannst Du diese Version des Feeds ja garnicht montieren, dass der Empfang so schlecht wäre. Also tatsächlich mal den LNB prüfen.


    vy 73,

    Michael