Posts by DH5DAX

    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,


    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.

    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

    not being on the slow side either, here's my setup:

    direct digital audio from vara modem into icom ic-9700

    gps-locked homebrew upconverter with commercial class A PA

    about 10 watts into 120cm with poty, but not 100% clear view to satellite, partially blocked by a wall and a balcony table

    I tried as well and it seems to work very very nice!

    09.10.2019 13:28:06 Connecting to IS0GRB... 1/2

    09.10.2019 13:28:16 Connected to IS0GRB

    09.10.2019 13:36:08 Disconnected TX: 111241 Bytes (Max: 3473 bps) RX: 127 Bytes (Max: 272 bps) Session Time: 07:52


    ** Messages sent: 1. Total bytes sent: 111113, Time: 07:46, bytes/minute: 14295

    *** Messages Received: 0. Total bytes received: 0, Total session time: 07:46, bytes/minute: 0

    *** Disconnecting

    *** Disconnected from Winlink RMS: IS0GRB @ 2019/10/09 11:36:08

    *** Session: 7.9 min; Avg Thruput: 14126 Bytes/min; 1 Min Peak Thruput: 14126 Bytes/min

    Quote from DH5DAX Michael

    He said "Because we are radio amateurs, not internet amateurs" did you miss that ?

    so what exactly is your problem here? Is it the distance between operator and radio? Is it network technology? Or is it internet itself? Did you miss that we are an scientific radio service and not a historic preservation radio application?

    So again, please let me know what your substantial problem with remote operations is - is it ony the term "internet"? Now imagine the very same technology used over hamnet with no internet involved. Is that still no ham radio?

    Please, don't be emotional about technological topics. Thank you.

    OK I see it, but you have to fix/mount the "sunglasses", otherwise it falls to ground. I mean the "eyeglasses frame".

    the fit is very snug on the octagon I used for experimenting, you have to force it on so it doesn't fall off even with some wind - I initially intended to make a 3d-printed adapter flange to fit around the lnb neck. that's what the three holes around the "nose dimple" were intended for. but as I already wrote, this was just one of my first dualband feed experiments which I have abandoned in favor of the G0MJW patch with waveguide feed. it is so convenient in many ways, the best I have tested so far.

    For a common focus of the array on a parabolic reflector I lack the physical justification, but I like to learn ... (stacking 4 LNB´s and gain rise up 6dB ? :-) )

    May I call you Schrödinger's Ham? ;) You are right and wrong at the same time.

    If we look at the near field, you are absolutely right, each helix of the array has it's own radiation lobe.

    But if we look at the far field, the individual lobes of an array combine into a single lobe.

    Getting far field conditions between the helices and the reflector isn't too hard at 13cm wavelength.

    Your idea with stacking four lnbs may even work in theory, but in the real world the stacking distance in relation to the wavelength might be too big to form a properly phased array.

    Have a look at this beautifully simulated example of a patch array:…h-antenna-array-in-3D.png

    Let's do the math. For a two antenna array I assume transition from near to far field at 2*(stacking distance^2)/lambda. For 13cm wavelength and 8cm stacking distance, this would be less than 10cm from the antenne (2*(0,08*0,08)/0,13 =~ 0.098). For the same stacking distance at 3cm this would already be almost 43cm (2*(0,08*0,08)/0,03 =~ 0,426).

    So if the distance between your "stacked LNBs" and the reflector is more than around 43cm, you should indeed observe stacking gain - but before you try, take into mind that you would need to phase the LNBs coherently with the same reference, otherwise phase difference would mingle with that gain.

    But that's only for theory. I tried the 13cm version and it worked not too bad. Now you go try the 3cm version and I will happily doubt your results afterwards.

    The cap is only to block off eventual DC on the input, so it isn't necessary at all if you feel lucky - but if you then by mistake swap the two ports, you end up feeding DC to your crystal which it probably won't like too much. The value isn't critical at all, as long as it passes your desired reference frequency.