Measurement of parabolic antennas

  • RimaNTSS:

    Der Abstand der oberen und unteren Befestigungsschrauben beträgt 350 mm

    Punkt G sollte nach den Messungen in der Mitte der unteren Schrauben, an deren Oberkannte liegen.

    Tatsächlich liegt der gemessene Punkt G um etwa 150 mm zu hoch, was an der Platte der Motorhalterung liegt.

    Die 8 mm Unterschied von FC und FD lassen sich durch Verschieben der LNB in der Halterung ausgleichen.

    Allerdings musste ich in der Praxis feststellen, dass eine weitere Entfernung von der Antenne ein besseres Signal liefert.


    The distance between the upper and lower fastening screws is 350 mm

    According to the measurements, point G should be in the middle of the lower screws, on their upper edge.

    In fact, the measured point G is about 150 mm too high, which is due to the motor mount plate.

    The 8 mm difference between FC and FD can be compensated for by moving the LNB in the bracket.

    However, in practice I have found that further away from the antenna gives a better signal.


  • EH is not perpendicular to AB, which means that in fact EH<279mm. This is in good agreement with the fact that the AB thread bends the CD thread.

    The slice of a parabola does not lie in the same plane.

    The upper part of the parabola is deflected relative to the lower part, possibly as a result of improper mounting of the antenna... :125:

  • Me neither :88: I am only sure that offset angle of Laminas 1.8m is 21.5* (it comes from antenna's datasheet), the rest of measured data come from other owners of that antenna (I do not even remember who provided this data to me long time ago). So, if AB=1935mm, CD=1800mm and offset angle is 21.5* and no negative coordinate of point B,


    It's not forbidden to have a negative clearance angle on an offset dish, is it?

    If I remember correctly, your SMW 1600 has a negative clearance angle? Or did we never definitely measure/calculate this?


    So why do you think it is wrong, a negative coordinate at point B?


    Greetz,

    A33

  • Hallo guten Abend strannik


    Zuerst wurde die Linie CD Mittels Schnur gezogen.

    Um die Halbschalen A und B zueinander auszurichten wurden links und rechts horizontal 2 hilfslinien gezogen. Mithilfe der rückseitig angebrachten zugschrauben wurden links und rechts soweit verstellt /angezogen bis die Schnüre sich leicht berühren.

    De Abstände AC CB AD DB wurden gemessen jedoch nicht dokumentiert, sorry. Wird alles nachgeholt sobald das Wetter besser wird.

    Im Anschluss habe ich die Linie AB gezogen und EH am tiefsten Punkt ermittelt.

    E/H 279 wurde so wie du es auf Bild siehst ermittelt.

    So wie ich dich verstanden habe, wurden durch die rückseitigen zugschraubenverstellung die Halbschalen verzogen und stimmen nicht zueinander, richtig?


    hello good evening strannik

    First the line CD was drawn with a string.

    In order to align the half shells A and B to each other, 2 auxiliary lines were drawn horizontally on the left and right. Using the tension screws on the back, the left and right were adjusted/tightened until the cords touch lightly.

    The distances AC CB AD DB were measured but not documented, sorry. Everything will be made up for as soon as the weather gets better.


    Then I drew the line AB and determined EH at the lowest point.

    E/H 279 was determined as you can see in the picture.

    As I understood you, the half shells were warped by the tension screw adjustment on the back and do not match each other, right?


    Ps:

    Ich Hoffe die Bilder sind erkenntlich..

    I hope the pictures are recognizable..

  • EH is not perpendicular to AB


    I have become an advocate of indicating the point where to measure the depth on the dish itself, by putting a dot there.


    I use this method also for multiple depth measurements, along the vertical dish axis, and along the horizontal dish axis.

    And I measure the distance of the depth measurement to the dish rim, not along the dish face (along A-B or C-D), but from the dot on the rim, to the dot on the dish surface.

    I believe that leads to 'stable' measuring of the distance, and less possible biassed error in the depth measurements (in the case of multiple location depth measurements).


    Greetz,

    A33

  • SMW 1600 has a negative clearance angle

    Yes, you are right. Also, SMW-OA-1400 "Jumbo" has this awkward negative clearance. But I think that SMW antennas can be put aside from all others. I think that manufacturers, during design of their models, always made this clearance positive or 0 (CM antennas), otherwise they would not be fully offset. :3:

  • Zitat

    The distances AC CB AD DB were measured but not documented, sorry. Everything will be made up for as soon as the weather gets better.

    It seems to me that you ignored my instructions regarding the markup of the Rhombus of the ACBD. You have a CD line drawn at the level of the junction of the antenna half-segments. This line looks higher than the middle of AB, and therefore the CD and EH are measured incorrectly.

    When the weather improves and you can return to the measurements of the antenna, start by marking the ACBD ROMB. At the same time, mark the found positions of points A, C, B and D on the mirror in the form of crosses 3x3 cm so that they are visible in the photographs. Then pull on the threads. First AB, then CD. If the latter immediately lies on the AB thread, try pulling the CD under the AB.

    Before measuring the EH depth, cross the H point and check that AH=HB.

    After determining the position of the point G, apply its cross, but with a pencil and not with a felt-tip pen.


    Good luck! :74:

  • I am familiar with this technique for determining the depth of a parabolic mirror, when it is not measured from point E to point H, but CE and CH are measured and according to the formula

    EH= sqrt (CH^2-CE^2)

    depth is calculated.

    In this case, the CH and CE measurement errors are squared and summed. The error of the result of calculating EH by this method exceeds the error of MEASURING EH (for example, with a caliper)


    Good luck! :74:

  • That is not what I meant.


    Imagine that you measure another dish depth, somewhere along the vertical axis of the dish, so with having new points E' and H', so to say.


    Since Paul Wade it was customary to then measure E'H' and BE' and BE'. BE' being along the dish face.

    I now measure E'H' and BH'. BH' being from dot on the rim, to dot on the dish surface. Though for calculation you need an extra calculation step, for measuring I find it more reliable.



    Why would I need multiple depth measurements along the vertical axis?

    I use it for checking/calculating offset angle on a multifeed dish. And for checking parabolical integrity of the dish shape.

    For the checking of parabolical integrity I also use multiple depth measurements along the horizontal axis of the dish.


    Greetz,

    A33


    Edited: and BE'

  • Habe ich richtig verstanden, dass alle Entfernungen, bei denen der erste Buchstabe F die physikalisch gemessenen Entfernungen von der Mitte des "blauen Kreuzes" in der LNB-Halterung auf dem Turm zu den realen Punkten A, C, B und D auf der Antenne ist?


    Wie wurde der Punkt G auf dem Spiegel gefunden, bis zu dem der Wert von FG gemessen wurde?


    Punkt E ist ein Fadenkreuz aus Fäden, die entlang der Diagonalen der Raute AB und CD gespannt sind? Wenn JA, welcher der Fäden wird zuerst gezogen?


    Danke für die Antworten auf meine Fragen.


    Gesundheit und Erfolg! :74:


    Did I understand correctly that all the distances in which the first letter F is the physically measured distances from the center of the "blue cross" in the LNB mount on the turret to the real points A, C, B and D on the antenna?


    How was the point G found on the mirror, up to which the value of FG was measured?


    Point E is a crosshair of threads that are stretched along the diagonals of the rhombus AB and CD? If YES, which of the threads is pulled first?


    Thanks for the answers to my questions.


    Health and success!



    Я правильно понял, что все расстояния, в которых первая буква F, - это физически измеренные расстояния от центра "синего креста" в креплении LNB на револьверном механизме до реальных точек А, C, B и D на антенне ?

    Как найдена точка G на зеркале, до которой измерена величина FG ?

    Точка Е - это перекрестье нитей, которые натянуты по диагоналям ромба АB и CD ? Если ДА, то какая из нитей натянута первой ?

    Спасибо за ответы на мои вопросы.


    Здоровья и успехов !

  • Erstes wurde richtig verstanden.

    Der Punkt G wurde mit eingespannten Laser im Feed gefunden und anschließend von F nach G mit dem Laser-Messgerät gemessen.

    Punkt E hat nicht mit Fäden zu tun. Die Mitte ergibt sich aus dem Kreuz der Befestigungsschrauben und einer Darüber liegenden Messlatte.

    Gemessen wurde von der Aussenseite zur Messlatte mit dem Lasermessgerät. Abzüglich der Stärke der latte ergibt die Tiefe EH.


    The first was understood correctly.

    Point G was found in the feed with a clamped laser and then measured from F to G with the laser measuring device.

    Point E has nothing to do with threads. The center results from the cross of the fastening screws and a measuring rod above it.

    Measurements were taken from the outside to the measuring stick with the laser measuring device. Less the thickness of the batten gives the depth EH.


    Первое правильно поняли.

    Точка G была найдена в облучателе с помощью зажатого лазера, а затем измерена от F до G с помощью лазерного измерительного устройства.

    Пункт E не имеет ничего общего с потоками. Центр получается в результате пересечения крепежных винтов и мерной рейки над ним.

    Измерения проводились снаружи измерительной линейки с помощью лазерного измерительного устройства. Меньшая толщина обрешетки дает глубину EH.

    Wer nicht die Antennengröße und den ungefähren Standort angibt, postet sinnlos, sofern es um eine Signalerfassung geht.

    If you don't specify the antenna size and the approximate location, posting is useless if it's about signal acquisition.

  • Danke für Antworten.

    So wie ich es verstehe, haben Sie die EH-Tiefe über dem blauen Punkt in der Mitte der Befestigungsschrauben gemessen


    88741-laminas-1800-focuspoint-2a-jpg

    Ist dieser Punkt viel näher an Punkt A oben an der Antenne als an Punkt B unten?

    Und noch eine wichtige Frage: Lässt sich die Kupplung mit LNB-Befestigung um 180° um die aus ihr herausragende Motorachse drehen?

    Wie groß ist der Drehwinkel der Kupplung mit LNB-Befestigungen um diese Achse?


    Thanks for answers. As I understand it, you measured the EH depth above the blue dot in the middle of the mounting bolts

    Is this point much closer to point A at the top of the antenna than to point B at the bottom of it?

    And one more important question: can the coupling with LNB fasteners be rotated around the motor axis, which protrudes from it, by 180°?

    What is the angle of rotation of the coupling with LNB fasteners around this axis?


    Спасибо за ответы. Как я понял, глубину EH вы измеряли над голубой точкой посередине крепёжных болтов

    Эта точка значительно ближе к точке А наверху антенны, чем к точке Б в её низу ?

    И ещё один важный вопрос: муфта с креплениями ЛНБ может быть повёрнута вокруг оси мотора, которая выступает из неё, на 180°?

    Какой угол поворота муфты с креплениями ЛНБ вокруг этой оси?

  • Genau, am blauen Punkt bei entfernter oberen Hälfte der Klemmschelle.

    Der grüne Laserpunkt in der Mitte der Schrauben ist nach A und B gleich, sollte laut Rechnung um etwa 15 cm tiefer liegen, an der Oberkante der unteren Schrauben.


    Die Rotorscheibe kann man ca um 150° nach links und rechts drehen. Umstecken um 180° wäre möglich dann sehen die LNBs nur noch den Feedarm, also sinnlos.


    Die in der Rotorscheibe befindlichen Gewindestangen lassen sich prinzipiell 360° drehen, aber nicht kippen.

    Wenn ich mich recht entsinne, habe ich einmal ein Zwischengelenk gebaut.



    Exactly, at the blue dot with the upper half of the clamp removed.

    The green laser point in the middle of the screws is the same after A and B, according to the calculation it should be about 15 cm lower, on the upper edge of the lower screws.


    The rotor disc can be rotated about 150° to the left and right. Reconnecting by 180° would be possible then the LNBs only see the feed arm, so pointless.


    In principle, the threaded rods in the rotor disc can be rotated 360°, but not tilted.

    If I remember correctly, I once built an intermediate joint.



    Точно, в синей точке со снятой верхней половиной зажима.

    Зеленая лазерная точка посередине шурупов одинакова после А и Б, по расчету она должна быть примерно на 15 см ниже, на верхней кромке нижних шурупов.


    Диск ротора можно поворачивать примерно на 150° влево и вправо. Повторное соединение на 180 ° было бы возможно, тогда LNB видят только руку подачи, так что бессмысленно.


    В принципе, резьбовые стержни в диске ротора можно поворачивать на 360°, но не наклонять.

    Если я правильно помню, я когда-то строил промежуточный стык.

    Wer nicht die Antennengröße und den ungefähren Standort angibt, postet sinnlos, sofern es um eine Signalerfassung geht.

    If you don't specify the antenna size and the approximate location, posting is useless if it's about signal acquisition.

  • is that your setup, this is impressive!

    Eurostar 240CM PF PF PAN DISH

    STRONG SRT 180CM PF PAN DISH

    STRONG SRT 135CM PF PAN DISH

    SSS 90CM GALVANISED OFFSET DISH


    VU+ ZERO 4K

    OCTAGON 8008

    UCLAN USTYM 4K PRO

    OCTAGON 88+

    TBS 5580 TV TUNER CI USB BOX [FAULTY]

  • Standard polarisation is horizontal (if the LNB is mounted in vertikal position) and if not both polarisations are possible (like an Universal-LNB).

    Wer nicht die Antennengröße und den ungefähren Standort angibt, postet sinnlos, sofern es um eine Signalerfassung geht.

    If you don't specify the antenna size and the approximate location, posting is useless if it's about signal acquisition.

  • Note that the ray tube power flux-density AF is higher than the ray tube power flux-density BF for the same phases of the converging spherical wave (darker shade of brown and wider "white" band).


    Given the fact that the density of the signal from the top of an offset dish towards the LNB is higher than that from the bottom of the offset dish, why don't you aim the LNB somewhat higher than along the bisector line F-G; for instance along the line to the deepest point of the reflector?


    Greetz,

    A33

  • Zitat

    Given the fact that the signal density from the top of the offset antenna to the LNB is higher than from the bottom of the offset dish, why don't you aim the LNB a little higher than along the F-G bisector; for example, along the line to the deepest point of the reflector?

    The aiming point G is calculated for CONSISTENT with the antenna mirror opening angle (which is also calculated in the PARABOLA program), LNB.

    If you irradiate an 84° LNB Inverto Black Ultra antenna with a 62° aperture, which is aimed at the G-spot, then you achieve a minimum of noise due to the mirror, but lose in the total power of the useful signal. Here it makes sense to "pull up" the line of sight of the LNB by 11°.


    If you only knew how many owners of the Russian SUPRAL antenna with an opening angle of 90 °, which they irradiated with the LNB Inverto Black Ultra, accused me of the fact that the PARABOLA program does not work correctly   :75:

    The program works and counts absolutely correctly, but it says in Russian that the author is NOT responsible for the misuse of its results.



    Точка прицеливания G рассчитывается для СОГЛАСОВННОГО с углом раскрыва зеркала антенны (который также рассчитывается в программе PARABOLA), LNB.

    Если вы облучаете антенну с углом раскрыва 84° LNB Inverto Black Ultra с углом раскрыва 62°, который прицелен на точку G, то вы достигаете минимума шумов из-за зеркала, но теряете в суммарной мощности полезного сигнала. Здесь имеет смысл "задрать" вверх на 11° линию прицеливания LNB.

    Если бы вы знали, сколько владельцев российской антенны СУПРАЛ с углом раскрыва 90°, которую они облучали LNB Inverto Black Ultra, обвиняли меня в том, что программа PARABOLA работает неправильно...

    Программа работает и считает абсолютно правильно, но в ней русским языком написано, что автор НЕ несёт ответственности за неправильное использование её результатов.

  • Well, it is clear that (the position of) the G-spot, as being the end of the bisector line of the dish opening angle on the dish surface, is calculated correctly.

    No doubt about that.

    But is the G-spot the best theoretical (and/or practical) aiming point for the LNB? In general, for a LNB-feedhorn matching the dish opening angle? That was what I meant with my question.


    Some time ago, when I discovered that the signal density at the top of an offset dish would always be higher than at the bottom of the dish, I concluded that it would be foolish to not use the higher density at the top of the dish, by keeping to aim at the G-spot. So that according to me, it would end up in finding a compromise between increased signal reception, and increased spillover loss, by aiming higher than the G-spot (more in the direction of the deepest point).


    At that stage I thought of an aiming point somewhere between G-spot and deepest point. But then I had a dialogue with someone who does calculations on those things, and he told me that his (theoretical) calculations led to deepest point of the offset dish as the aiming point, to start with.


    The beauty of aiming at exactly the deepest point of the dish, I reasoned later, is that exactly half of the reflected beam then arrives from the top side of the LNB, and the other half arrives from the bottom side of the LNB. That seems to be a symmetry, not to be ignored, I thought.


    Now of course there might be mitigating factors, in spillover, noise temperature, non-matching feeds to the dish, etc etc.

    But for me, the G-spot is not the primary aiming point anymore. I've switched to preferring the deepest point of the dish as the primary aiming point for the LNB. Though of course there might still be all sorts of practical issues and influences, which could shift the best aiming point away a bit...


    Greetz,

    A33

  • Here the Point G on a Laminas 1200 with original feed arm.

    It's a few mm left of center and roughly corresponds to point H.

    EH = 113 mm



    Wer nicht die Antennengröße und den ungefähren Standort angibt, postet sinnlos, sofern es um eine Signalerfassung geht.

    If you don't specify the antenna size and the approximate location, posting is useless if it's about signal acquisition.

Jetzt mitmachen!

Sie haben noch kein Benutzerkonto auf unserer Seite? Registrieren Sie sich kostenlos und nehmen Sie an unserer Community teil!