Obnelly1:
Dear Geometry,
This is to show my little appreciation for sharing your knowledge about how parabolic antennas are made.
I was inquisite to know how it's made right from 2002 not until I stumbled on your thread .you actually break everything into shambles for people in a commercial class or art class to understand it better.i can never thank you enough.
Why I am thanking you is when I saw that massive 5m you constructed i say to myself one day i will personally and single handedly fabricate 5m without no assistance and 10 yrs after your thread I made a monster 5m for myself and for others who might be interested in such massive 5m.
Geometry ,you are one in a million I cant thank you enough .
Today I can identify fibre matte of various grades, saturated polyester, cobalt and catalyst .improve myself ON metal fabrications ,welding and painting,INSTALLATION AND TESTING OF 5M PRIME FOCUS ANTENNA DISH.
GEOMETRY YOU ARE THE KING OF ANTENNA IN AFRICA.
THANK YOU SO MUCH FOR EVERYTHING .

I now owns a workshop for making 3m_5m prime focus antenna dish .

I am overwhelmed by these accolades! thank you, fellow... to all that have trodden a similar path in bringing knowledge to life.. kudos. Just remember the journey to meet up with the rest of the world is ahead. I have always believed we can do it... even more and better... we all know what the stumbling blocks are but, we can use the huddles as stepping stones to get to where we need to be... I thank you for the acknowledgement... I really appreciate it.

Maureenapp:
Hello sir, please when a Cband dish is written 7.5 antenna does that mean that the dish is a 7.5cm dish, because I requested for a 2.5cm dish, and what I got from the seller is 7.5 antenna. Meanwhile which Decoder do u think is best to use for it sir. Please answer because my question is very urgent

I am sorry for responding to this question late, for some reason, I must have missed the notification. can you share the photo of the dish and the page on the manual where the ''datasheet'' of the DISH reads 7.5 or 2.5... that way we can move forward in solving the riddle. as for the question of which decoder to use; most decoders have the capacity to receive both C-Band and Ku-Band.... its the programming that you would need to do to select what band of signal you are trying to receive... bare in mind this has a lot to do with your dish size and the signal footprint at your location. plz, share the datasheet of the dish you received from the supplier... in other to move forward

midozalouk:
Hello sir
Since we are in 2020

Can we use 3d printer to fabricate the dish
And cover the surface with Aluminium foil to reflect the signal
Or I am wrong?

Thanks sir

I replied this message but don't know how it not showing on here.... Yes, we can 3-D print anything pretty much these days... the same thing applies to a satellite dish, in parts (petals).... that has to be a big 3-D printer though...

anorld054:
No measurement of the arc (i mean the radius) except the diameter and the dept does all.but the dish above is molded 5 years now, so i need help. Thank you.

Hey, anorld054 ... what are your Diameter and Depth values?

mrklock:
good day Mr. GEOMETRY please can you post the pix of the materials needed. i'm having difficulties getting them in the market

@mrKlock, sorry for late response, please, accept my apology. If you stay in Lagos, there are several locations at which you can make your purchase... seeing your post have made a request of a good supplier. I intend putting his shop location on here for any one having similar issues.... in the interim, I am attaching a google map with an approximate ''spotting'' here we go:

https:///maps/uUGxeNKzhjA2

at this location ask of ORISTO that sells chamicals,

HE GAVE ME PERMISSION TO OFFER HIS NUMBER TO CALL FOR ANYONE THAT IS MAKING A PURCHASE, YOU MIGHT WANT TO CALL BEFORE STARTING TO GO ... 08037120177.
HOPE THIS HELPS.

safex:
This thread is supposed 2 b active always; wia is @geometry abeg?

@safex, I am sorry, had problem hooking up with ''fluidy'' internet and that was a little frustrating, i apologise for my absence, what do you have going ?

Iron2011:
@ geometry. I have a dish that I want to paint. Most online suggestions say that , the paint must be a flat/ matte paint. However, I have been through most paint shops. However, they don't understand the meaning of flat/ Matt . nothing of that sort is also written on their containers. The only one I saw was an emulsion paint with the Matt written on it.
Any help? Counting on u to select a paint.

@IRON, use gloss paint, ''grey/arsh'' is acceptable because of its property as regards radiation reflection, protecting your LNBF from being heated

joehis2013:


Is that possible

I have never tried that, AND I MUST SAY:, I doubt the possibility of it. Remember, satellite signal tracking/practice is a precision technology!

safex:
Chai! Dis one na advanced further mathematics o; as e don tey wey I don comot 4 secondary school. LOL

@ Safex, I was just trying to follow up your solution but, in case someone doesn't know the dish focal length (f), measure the DIAMETER ''D'' and the DEPTH ''x'' then, D/16x gives f/D ratio, is a short cut to get the focal length too by manipulating the formula... [I am still waiting for your email].

safex:

Simply divide ur focal length by dish diameter

measure your dish DIAMETER = D, and DEPTH = x,
Remember the formula, y^2 = 4ax; hence, y^2 = 4fx, i.e, a = f = focal length.
HINT: y = D divided by 2.
D/2 = y.
(D^2 means D squared).
therefore; (D/2)^2 = (D^2)/2^2, = (D^2)/4.
So, (D^2)/4 = 4fx
(D.D)/4 = 4fx,
(D.D) = 16fx,
D = (16fx)/D,
D = 16x(f/D),
also, 16x(f/D) = D,
(f/D) = D/16x,
f/D = D/16x.
in other word, if you know dish DIAMETER & DEPTH, you can evaluate your f/D ratio.
but if your focal length is given as is most like in the ready made dish, just divide it with the dish diameter.
I HOPE THIS HELPS, IT'S A REMINDER, I BELIEVE WE HAD IT SORTED OUT ALREADY IN THE TREAD EARLIER ON. PLEASE, REVIEW.

safex:
@geometry hop u saw my msg in ur inbox?

honestly not yet... again; olammy77@yahoo.com

obnelly:


No .Deep doesn't mean it get more satellite deep means terrestrial interference have little effect on it unlike its partner shallow.shallow is good but its problem is earth interference.so to me your choice of f/d has to do with the degree of interference in your site.deep dish may be good in your area while in my area its shallow but the bottom line is the which ever you choose .you Will still get good signal .
Goodluck

ABSOLUTELY,... terrestrial interference is paramont on shallower dishes and less on deeper dishes ! why?.. because of illumination angles difference in both ... read more on the subject. but, research so far has given us some range that allows us to play safe anytime we have new TVRO projects, as illustrated on the tread long time ago, this had been given in the form of F/D ratio that is, the relation between focal length and Diameter of the dish which has direct relation to shallowness or depth of the dish. ... as a recommendation ...; F/D of between 0.35 - 0.45 iS GOOD FOR OUR TERRAIN, WEST AFRICA or AFRICA in general. ... when we are tending beyond this RANGE, I suppose its safe to opt for OFF-SET arrangement... I hope this is found helpful to all DIYers. cheers

safex:
I've just done dat. Fenks

did not see your mail yet, can't find it.... still waiting... wish w ecould get solution to your quest here ...
Cheers.

safex:

Oh, dat's gud. I rilly wanna hav som chat wif u. Can u plz provide me wif either of ur whatsapp number or bbm pin if diaris. Fenks

olammy77@yahoo.com ...HIT ME WITH YOUR CONTACT DETAILS...
THANKS.

safex:
Wia has geometry gone to sef?

alright, I am here... I respond whenever I have me mentioned as it would give me notification through my email ... thank you all

Smilelo: So how can someone contact u if he/she needs u to do a 6meter or 5meter dish for him because I want to get Sky uk.

I am in town, plz, all let set the ball rolling...

@ Iron,
There is nothing as fulfilling as coming to an ending of a project, and in flying color... I MARVELED at the courage you guys summoned to come to this point of the project. I BELIEVE TO ME AND SO MANY DIYers, IT IS ANOTHER STEP FURTHER IN OUR GOALS AND AIMS THAT IS WORTH CONGRATULATED.
PLEASE, I WILL FIND TIME TO ANSWER A FEW QUESTIONS AS POSTED ABOVE. ONCE AGAIN, CONGRATULATIONS TO YOU AND ALL DIYers.

Adewunmis: someone should save worry,i'm confuse about the bottom of the dish,the "U" mount is what am confuse about pls geomentry to continue with this thread,it beginning make some senses. .pls i begged u lets move on.

.

PLEASE, WHAT DO YOU WANT TO KNOW ABOUT THE BOTTOM OF THE DISH ?

Adewunmis: pls how can i meet you cos i like u put tru on how to construct mold

...please, read through the tread, its all encompassing as regards making molds,... all questions are entertained though. Pick one or two things from what was previously discussed then see how it is applicable to what you intend doing , design as in dish fabrication.... we can all learn from you too,....

cleverdiva: @geometry

Pls I am working on the design of a triple lnb dish for my final year project. After going through your work here, I wanted to know if you could put me through the designing of this kind of dish.
Cheers!

Well, I have not extensively have a serious practical input into that aspect of satellite signal tracking, I can explain how it works, but practical aspect is another experience entirely,.... theory would only guide you of doing it right even when your efforts have not yielded result... but, somehow I have seen people here recording sound success on the multi_lnb stuff, ..just search further on Nairaland ,...sorry,...just can't remember where....

WELL,.. ALL ALONG I HAVE BEEN DESCRIBING IMPROVISED ADJUSTABLE COMPASS, YOU WOULD NEED A PROTRACTOR TO GET YOUR CALCULATED ANGLES FROM THE CENTER MARKED BY THE SHARP POINT OF THE COMPASS,(PIVOT),....THE REST ARE STRAIGHT EDGE AND MAKERS,.... lol

obnelly: Does that mean we can make 5 different dishes of various sizes from that last diagram?Also in fig3 i think we would need something like a protractor for us to get the best of that angle.

...and also, on the protractor stuff,.. we are going to need one !,.. we can improvise, i.e make solid length of light square pipe and wear a bigger sleeve square pipe on it with an arrangement that can hold a scribber;.. that could be a maker, pencil, pen etc. I will try and sketch something out as an example of what I have always been using in case i need to do something like that.... then you can determine your radii... REMEMBER; FIGURES 3 IS A TRIANGLAR REPRESENTATION (AS REPRESENTED IN 2-D)OF CONE FROM THE RED SHAPE INDICATED IN FIG 2,.. BUT AS A SECTOR IN FIG 3...

obnelly: Does that mean we can make 5 different dishes of various sizes from that last diagram?Also in fig3 i think we would need something like a protractor for us to get the best of that angle.

sure we could but not advisable in the orientation the set of triangles, the diagram above is for the procedure in making a development for PETAL in ''sectionalized'' dish. I will go further in the explanation of it as soon as I have the time to do so.

REMEMBER, THE DEVELOPMENT CONCEPT IS MORE FOR BOYCOTTING THE CONCRETE MOULD CONSTRUCTION,..and having sectional dishes.

sorry for the repetition, i am trying hard to get a clearer diagram for better viewing ,.. lol

FIG 4, AGAIN in Jpeg

FIG 4;

sorry this came late,..

[img][/img]

@Obnelly,
I tried as much as possible to steer away from INTEGRATION & DIFFERENTIATION,..I am aware of the fact that not everyone on the thread are from engineering background, lol. this is just a mare high school MATHEMATICS,..I put in serious effort to come up with such simplification,... CALCULUS would have been the best tool, but might be quite difficult for non engineers to handle... yeah!

I SENT THIS WITH THE PICTURE, OBVIOUSLY,, I HAVE DONE IT THE WRONG WAY, MIGHT HAVE TO TRY AGAIN TO UPLOAD THE ILLUSTRATED DIAGRAMS,
THANKS.

...It is a new dawn, hello, people!,HERE WE GO;





Development Drawing for a Sectional Paraboloidal Surface.
GENERAL;
The concept of development drawing explains how we have a plane representation [2-D] of yet a somewhat complex GEOMETRY of figures or shapes in engineering. It is what we have employed in cutting out metal sheets before stamping/forging into whatever shapes in AUTO and CLADDING/CONSTRUCTION industries, to mention a few of its applications.

SCOPE;
Development Drawing for a Section of a Paraboloid.
We need to get familiar with some terms, a lot of which we have come across at one time or the other;
Parabola – 2-D geometrical representation with standard mathematical equation; y^2=4ax.
Paraboloid – 3-D Geometrical representation of parabola. Paraboloid is generated from parabola.

PREAMBLE;
We need a quick journey to our high school day geometry class, specifically MENSURATION under which several shapes were thoroughly addressed. In this discussion, we shall make mention of shapes like; Cone, Sector, Triangle, Parabola and Paraboloid. In actual fact, the two later shapes were not extensively dealt with during high school day but, let us see how we can play around these shapes and figures that describe them and come up with something tangible that can be useful to us.
Before i proceed, I am going to take a hypothetical example of a project undertaken by a DIYer, on this tread, the terms. I promise, are going to be those we are familiar with, perhaps, a few strange terminologies but, I bet they could be linked with what we are familiar with, especially, if we had been part of DIY on Nairaland.
We are going to look into a parabola of 250cm in diameter with F/D ratio of 0.4, we remember the
equation of parabola to be y^2=4ax ---- (1), a and 4 are constants of the equation. And a being the focal length of the parabola, usually denoted by F.
Then, we can write; x=y^2/4a
Hence, x=y^2/4F ---- (2).
Remember x is the depth our parabola;
F/D ratio IS 0.4,
Hence, F/D = 0.4 ---- (3).
We can therefore obtain a value for x;
F = 0.4*D.
= 0.4D
= 0.4 multiplied by 250
= 100cm.
What this translates to is that the distance from the center of our parabola to a point 250cm equidistant from the edge or circumference of the paraboloid.
Alright, let us see what x is in value;
From equation 2,
X = y^2/4F,
Therefore; x = y^2/4*100.
Y = radius of the parabola; = D/2 = 250/2 = 125.
Y = 125cm.
Hence; x = 125^2/4*100 or 125^2/400.
= 39.0625cm.
So, our parabola is 39.0625cm deep.
That is that about our parabola.
Now let us discuss making a development drawing for a section of this parabola:
First of all we need to know how many division we are going, also, we should know that the derived development has its effectiveness hung on two main factors;
(1) The number (n) of divisions - The more the number (n) the better the resulted obtained.
(2) The depth - The shallower the parabola, the better as well.

MY ADVICE;
*adopt as many divisions (n) as possible.
*Chose a higher value of F/D ratio.

At any rate, we are sticking to our hypothetical example.
Thus;
F = 100cm
X = 39.0625cm
D = 250cm
Y = 125cm.

Reasons for Conception of Development Drawing Technique.

Well, some of us might be wondering why the worries about the Development Drawing Technique, is it really worth the trouble? My reaction would be; yes! If you have ever been in the trade, you would have, at one time or the other, given the idea a thought, considering the effort required in making a whole MOLD and transporting a fabricated whole PARABOLOID, (BUD).
Reasons;
(1) We can by-pass making a whole MOLD if we can work hard on Development Drawing Technique to achieve good result.
(2) We can achieve petalized paraboloidal sections which can be coupled together to form a whole Paraboloid.
(3) We can safe on cost during transportation, since petals would not require hiring big truck for delivery. Especially, when dealing with BIG BUD.

CONCEPT/PROCEDURE
HINT;
I need to mention that the concept is more of an analytical process than drawing, we need to know why our points are where they are and there must be basis for all comparisons. There for we support all our argument with simple mathematical analyses.

The first thing to do is to imagine a CONE in our PARABOLOID, inscribed, having the same height and base properties. For simplification, I have adopted the usage of colours to distinguish sketches for CONE and PARABOLOID; red for CONE and green for PARABOLOID.
In 2-D representation, we see a RED triangle inside a GREEN parabola, both having equal height and base. Therefore, same base circumference.
Next, we need to remind ourselves that a cone is derived from a sector of a circle.
Now, let us find out what our sector looks like that gives us the CONE inside our PARABOLOID.

In FIG. 1 and FIG. 2,
The slant side of the CONE is indicated by, l, its height by, h and its radius by, r.
HINT:
The arc length of the sector that forms this CONE is equal to the circumference of the base of the CONE, and this is same value as that of the circumference of the base of the PARABOLOID.
Let us see what we have;
Arc of the sector = base circumference of the CONE and that of the PARABOLOID.
Therefore,
2[PIE]r = base circumference.
= [PIE]D
= 250[PIE]
HINT;
The slant side of the cone has equal value as the radius of the sector, l = r’
Apparently, we figure out a circle of radius l, from which the sector that forms our CONE was cut.
This sector would subtend an angle called Theta.
Theta/360 = arc of the sector/circumference of the circle with radius r’
Theta/360 = 250[PIE]/2r’[PIE]
Theta = 360*250[PIE]/2l[PIE]
Remember r’ = l.
Theta = 360*250/2l
From FIG. 1,
(AO)^2 = (OO’)^2 + (O’A)^2, Pythagoras; right angled triangle.
AOl,
Therefore, l^2 = (OO’)^2 + (O’A)^2,
= h^2 + r^2,
= 32.0625^2 + 125^2,
= 1028.0039 + 15625,
= 16653.003,
l = \/16653.003, i.e, (square root of 16653.003),
= 129.045651cm.
and Theta = 360*250/2l,
= 360*250/2*129.04651,
= 348.71151
= 348.7 deg. ~ Approximately.
As indicated in FIG. 3, If we draw a circle of radius 129.05cm and measure an angle of 348.7 deg. The sector that subtends this angle would form the CONE that we earlier inscribed in the paraboloid.
And we ought to remind ourselves that we have a number (n) of division. We will later discuss how it is relevant to our Development Drawing.
As earlier mentioned, if we cut off the smaller sector that subtends an angle of 11.7deg. the bigger sector left behind would form a CONE, when its radii lines are brought together. This cone is our CONE, having an height of h, which is equal to x and base circumference of (Theta/360)*2l*[PIE].
= 348.7/360*[PIE]*2*129.05
= 785.7096
= 785.71cm.
Comparing this value with the circumference of the paraboloid;
2[PIE]r
= 2*[PIE]*125,
= 250*[PIE],
= 785.7142,
= 785.71cm. QED.

EVIDENTLY, THESE TWO VALUES ARE PRACTICALLY THE SAME.

I apologise to keep typing Theta, I could not find on my key board the key that gives me the appropriate symbol for angle, so also, some of my spellings, lol.

....................TO BE CONTINUED....................









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