₦airaland Forum

@ swordswifter,
i guess your dish is kinnda' too flat for acceptability. the acceptable range i know for f/D ratio range is 0.3 through 0.7 , for [TVRO] (Television Receive Only), yours might be a kind of push to the edge and i hope it works for you.
i 'l like to see your result for comparison, and maybe what you have supersedes the previous records. it could be a land mark, but then i'm afraid.
let's hope yours is a landmark success.
plz, feel free to let us have your results.
thank you.

@ newtonn,
the post with illustrative diagram is sort of self explanatory. I distinguished the 'theory' from 'actual'.

@ dodos & all, There is a standard for lnb holder size, i.e, where holes are drilled, generally, this gives precise idea of what parameters to base your calculations of tripod length. That is why i stated in the previous post to go by 'actual' and not 'theory'. There is slight defence between the results from both instances. Check out the post with illustrated diagrams.

Members of the floor i meant.

@ Swordswifter,
that's what i'm talking about ! You are great ! Now that you are breaking the ice, let's go !
I strongly anticipate other members of this members to emulate this move of yours.
I'm waiting for your results. Goodluck. What size is THE PROJECT by the way ?

Plz, remember to mark the middle after transfering your measuement over to 'STIFF' square pipe.
Cheers.

@ all,
Measuring Dish Depth:
the rope method is good, but you need the point on the rope to measure to. Thats the mid-point on the rope which is now the apertural center of your dish, i.e, the effective surface area. Invariably, the distance between the marked point on the rope and the center of your parabola (dish) is your depth. Now let's method another method.

'STIFF PIPE METHOD'

most tripods come in 1/2" light square pipe, before cutting measure out your diameter, mark out the two endsthen, the mid way which is your radius. Place the two ends on the rim (edge) of your dish such that it divides your dish into two equal halves. This is obtainable by making sure your two end marks coincide with the two opposite points on the edge of your parabola (dish). The simplest way to archive this is to, first of all, measure your diameter with a tape and then transfer over to your yet uncut square pipe.
Latter we will discuss TWO-TAPE-METHOD.

@ lovala,,
you are right !
@ newtonn,
you wrote 160cm then bracketed 1.8m. But then, since you said your dish diameter is 320cm right from time, i assumed your your bracketed 1.8m is meant to be 1.6m. Plz, comfirm it.

@ Newtonn,
ur tripod = 167.6cm long.
ur focal lengh = 123.1cm.
Goodluck !

@ all,
plz, point of correction , where i wrote stick to theory i meant 'actual' ,and my equation, instead of h^ it is h^2,
i.e, h^2 = a^2 + b^2
in statement ; square of hypotenous = the sum of the squares of the rest two sides

@ Newtonn,
your dish looks like its from a good mould, try and protect it from damage by allowing it collect rain water., just turn it upside down. goodluck.
again your tripod length is (t) actual.
if any other things , feel free to ask.

@ newtoon,

remember pythagoras theorem ?
consider the two diagrams ; i.e theory and actual. stick to the theory. it gives you the actual tripod length with just little adjustment to actual focal length of your parabola [dish].
pytagoras states that; the square of the longest side (h^2 ) of a triangle is equal to the sum of the squares of the rest two sides
( a^2 + b^2 ) . i.e h^ = a^2 + b^2
in the case of the represented diagram ,

h = t,
a = line CB,
c = line AB
FOR CLARITY SAKE, in the actual diagram, there is a value for s , which is the radius of the scalar ring. the same value goes for ku- band lnb holder as indicated in the diagram.
by using my vernier calipers i got scalar ring diameter to be 16.5cm i.e the radius comes to 8.25cm which is (s)
hence; (a) = line CB = radius of the dish - s . i.e [DIAMETER/2] - 8.25CM.
(C) = line AB = focal length - x. i.e f - DEPTH, = f - x,

don't forget x represents how deep your dish is.

Newtonn, do you see why u need to measure your dish depth ?

@ newtonn,
get your dish depth (x) & i will give u ur tripod length. I will some sketching and post when i get back home. I have being away 4rm my system 4 d past few days. Though, its not complex.

@ twinskenny.
for a properly configured neck for smooth motorization, 3m, fiber dish, 08033926638.
people complain about the cost, but no one ever regretted. that is a warning though.!

@ all'

microgi@nt has given us a very handy tool, software, the "PARABOLA" calculator, try and download it and fix your values . it serve as a mini simulator to some extent. i have used it it works very ,very well. anybody can try it.
THANK YOU Microgi@nt. http://www.files.com/file/4dd0ec433c179/Parabola.cab

@ twinskenny,
your location ,plz. is it meant for motorization?

@ Dodos,

plz, forgive me, right now we can only come up with a group of clumsily arranged pix, that might cause more of confusion than clarifications.
at what level are you in theoretical analysis of what size you are willing to experiment upon? if any, plz , let me know.

@Life 707,

1] you don't need a real dish to create a mold in actual sense of it, but if you interested in pirating a dish, ba wahala ! we can go through that latter. but you need to be sure the dish you are copying is exceptionally perfect. also , don't expect too much from your pirated product. alas!

2] a successful mold fabrication can give you 1MILLION copies of dish from it.so , is not every time that you will need to make a new mold.

3] As for how to make mold, just follow the sequence the proceedings on this forum, and ask questions that are peculiar to your stages in the process.
remember you are always welcome.

@ Eltonluigi,
There is no arm in trying new things sometimes. you know !?

@ Ilish,
hey, why not try from smaller and latter proceed to bigger, say, 1.2m or 1.5m, reason being that if there were mistakes you would have courage to try
next time.

@ swordswifter,

Let us see what happens at the labelled position A, B and C respectively.

@ A;
The [A] is recommended by most designers, but in theory, the measurement of focal length
is to the PROBES.{two silvery or golden appendages emanating from the wall of the wave guard when
you look into the LNB from [A]}.one very important reason for A as location for focal point is due to
imperfection as a result of human error during mold making and satellite DISH fabrication. so not all
signal rays are specifically brought to focus, another reason is the fact that signal rays coming from
transponders are not absolutely parallel. hence there are bond to be some slightly off-focus converged rays.
so we need the space between A AND B, usually cylindrical or rectangular, to convey these rays to the probes
at B.Note that the oncoming electromagnetic waves from space is mechanical in nature and after convergence
are set to oscillate the probes.

@ B;
This is apparent location of the probes, but before B, let's see what happens between A and B: Here,
the slightly unfocused rays are collected and redirected, through constant reflection as they bounce
against the wall.[wave guard], this process contributes to the overall gain instead of just escaping the focus.
We can now visualize the reason for a need to have a receiving area bigger than a DOT as theory would imply.
Now at B, the collected electromagnetic waves set the probes into RESONANCE, and this message is transferred to
the electronic circuit connected to the probes, the circuit ,in turn, converts the received message to an
electrical impulse, in form of current in milliampes.(mA).

@ c;
This is the gateway to the processed signal to the the decoder in form of electric current in a very low
amperage.your decoder then interprets this to what you see as signal strength and quality.and consequently,
pictures and sounds.

CONCUSSION;
*Point A remains the best in practice.
*Point B only exist as supposed location for focus,but not accepted in practice because of human errors
that are abound during mold making and dish fabrication.

***HINT;
when you cut your LNB,one of what you intend doing is bringing your probes CLOSER to the focus,
BUT DON'T QUOTE ME ON MY LAST STATEMENT, IT IS WHAT I THOUGHT IT SHOULD BE. but i'm sure.

@swordswifter

It is best at [A],
u cannot believe it, the ntwk just messed up my write up, the details of what happens at each position. i have to leave for somewhere right now, maybe, when i'm back.
see you guys.

@kinsmen2004
He want to stay ahead of the chart we dey pull am

OKA RE O , SO TI GBO. !
DIDN'T HEAR FROM YOU AGAIN. HW FAR ?

relax, the pix will come , but then , understanding of the theory makes your job easier when u are finally ready for the mould.

@cogitoErgo
Those things are available, mostly where chemical substances are sold,if there any in ur area. as for the metallic fabrication; it is a little bit difficult playing with steel, aluminum, etc than fiber glass materials that are liquid and semi solid before curing. fiber glass is easier when you get ur mould right !

@loluskysat,
, AND not anywhere near Abuja ? can u give precise history of antenna installation in Abuja to know Exact size good for it.

@george
thanks a lot. i do this with all pleasures.

@sathob
i'm more than impressed with your determination and what u eventually came up with. i am quite sure u can feel how easy things can get when u are determined. Now,using ur graph software. hint; adopting same scale i.e 10:1, specify your actual dimensions on both axes.remember same scale on both of them.plz, u can call if anything seems confusing, +348033926638 (08033926638). then determine what u have as ur focal length and subsequently ur f/d ratio. I am waiting.

@loluskysat
have u considered 3m.,? cos 3.5m is one size that is not easy to come by. better still, 4m. Are there no satellite fabricating 'shops in ABUJa ? pls let me know.

Is the focal length f is the distance between the focal point to the bottom of the dish or the center of the brim?
What can I use as the mould?
^^^THE FOCAL LENGTH IS THE DISTANCE YOUR LNB SUPPOSED POSITION AND TE DISH CENTER. NOT THE RIM(APERTURE) CENTER.

@ayibatonye
i want to believe you already have the stations to be transmitted received.! "paraphrasingly"; you need a number of decoder equivalent to the number of channels to be rebroadcast, at least,modulator(S), a transmitter ,with a capacity, depending on your intended coverage. your coverage is important other things might necessary , i.e , obtaining a license. these are basics. and am of the opinion u are considering wireless.

most satellite antenna employ the principle of PARABOLA, the equation is y^2= 4ax,
y = radius of your dish, i.e , half of the wideness of your dish,
x = depth i.e , how deep is your dish,
a = (f) focal length , i.e , how far away from the center of your dish must your lnb located,
4 = is a mathematical constant.
for the equation , one can rewrite ,; y^2 = 4fx.
try the curve fittings on a piece of paper, start by making x the subject of the above formula i.e , x =y^2/4f.
just like your everyday elementary school days graph, draw a chart of two rows and first column for x and y
remember that y is the half of your dish (PARABOLA) ,find different values of x at varying values of y in the equation.
for instance, if you have chosen to design a 2m dish, i.e 200cm, vary the value of y @ say 10cm intervals, the you have 20 points to be linked on your curve.
can anybody try this and let see what he has. it doesn't hurt at all to try. , as easy as chicken soup. let's go.!
i suggest you chose a scale of 10:1
HINT; y^2 means y squared  , that is, y raised to power 2.