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Dear friends.....
I have a problem with my C band setup.
I have got a 2.00m offset antenna (2.04cm height, 185cm width). Atttched is an Orthomode chapparel feedhorn with dual band having 17K nextwave LNB's on it and a Conical Scalar feed (which i purchased recently).
Tried to setup my dish at 68.5 E, Intelsat 10.
Following are the the transponders with there signal qualities.
Transponder Signal Strength Signal Quality
4064 H 69% 63%
4127 H 69% 45%
3864 H 67% 20%
3774 H 67% 20%
4143 H 67% 20%
3836 H 67% 20%
4124 V 65% 40%
4178 V 65% 59%
4034 V 65% 20%
3913 V 65% 20%
My problem is with the ones with RED having 20% quality..... Few weeks ago friends (bassett) from here adviced that it is because of the wrong scalar ring. I had a prime focus scalar ring before...but now i replaced with the appropriate one which is the conical offset scalar ring but except 4127 H which was giving 20% increased to 45% the rest remained the same as before.
What mistake am i making.....What if i change the LNB's with 13 K. Will the signal levels increase.....
Please help me with this problem.....
My location is Ankara turkey (39 North 32 East). According to Lyngsat i am able to get the H and V signals with 1.80m-2.00m antennas.
Waiting for your valuable comments....specially bassett and other friends....
Rgds
Nasir
" 李俊明 Born To Help People "
DM 500s , Pacific 3600 CI , Humax F2 Finder , Angel Box , My Dream Machine , Tatasky , KAON , Topfield 3030 , Yuri YR1Dap , Dynasat 7100 , F1 , Plus and II , Metabox II , 10 , Viva Vs 9000 , SkyBox II , X-Sat 430 , 420 , Bolt N2 , NewB , New Shine Ns 3000 , Victory V 889 , F1 Newshine , New Star , Innovia 3088 CA , Atom 7000 , PBI , Prosat , Dstv 3Q76 , GA 88a , Tatasky , Big Tv , Airtel .
Thanks but this does not solve my problem....
It is easy to buy something new but is difficult to tackle with things....
To solve a problem...its good to tackle....
Waiting for your comments people......
Rgds.....
they all should be better given the size of your dish, two things you could try, Optomise your "skew" of the LNB. By looking at your frequancy list, two transponders are strong, the rest are weak, and th strong one's are Verticial, All the horisontal transponders are weak.
mark the position of the LNB, in the Scalar ring, with a felt pen and slowly turn the LNB to see if th signal strength increases on the Vert transonders, Then mark the spot, Then turn in the reverse direction until the Horz signals increase, mark the spot. then set the LNB between the two marks.
You could also adjust the LNB focal length, this could affect the signal strength, by way of the reflective coverage between dish and scaler ring.
I would doubt that the focal length is out by much, as it is working to a degree, and the calculations are quite complex, unlike a Prime focus dish set-up. I have posted the formula below, for your referance.
Calculating the Focal Point of an Offset Dish Antenna
It is assumed that readers know how to calculate the focal point of a symmetrical parabolic antenna. Offset antennae are a different matter. The popular belief here is that the focal point can not be established by simple means. However, this is not correct.
To establish the focal point of an offset antenna, we need to measure three parameters instead of two: the large and small elliptical axes and the maximum antenna depth. The bulk of an offset antennae is formed by a three-dimensional space (Fig.1a). The similarity of offset antennae is determined by two parameters, but no explicit expression is available. The principle of offset antennae is described below, and the parameters and marginal conditions required to establish the focal point are given. A listing of a small BASIC program is also included, together with some checking calculations. Fig.2 shows an offset antenna with an even lateral face.
It emerges as a section of a cylindrical paraboloid which is divided by a cut. With a little effort, we can prove that:
1. Penetrating the plane and the surface of the circular paraboloid gives an ellipse
2. Projecting the penetration onto a plane running at right angles to the axis generates a circular line.
These important findings make it possible to establish the correction angle for the edge of the offset antenna:
w = arctg u
An equation can also be derived for the co-ordinate, x1: For the focal point, the position is as follows: The correction angle can be derived from equations (1) and (2) if it has not already been given by the manufacturer. There is a simple method by which it can be calculated from the reflector width. It is more difficult to solve equation (3). It can be solved, for example, using the small BASIC program, or with a programmable pocket calculator.
First we must delineate the areas on the x axis which lead to unambiguous solutions for equation (3) for f > f together with z2 > z1. Fig.3 shows the interval selection for the solution of the equation by means of interval halving. We begin in the range x < f, which emerges as the penetration of the two intervals referred to. If no solution is found, the search is continued in the range x > f. It is advantageous to select the interval dx - b. It can be shown that in (3) a (+) in front of the root for x > f never leads to a solution.
If no solution has been found, the areas outside the brackets, which have so far been established as the standard accuracy, G = 0.001 (in the program), dx = accuracy, b = DX (in the program) or N = 1 (dx - Nb), are expanded. We now select a G < 0.001 or N > 1. The co-ordinate x1 is established with an accuracy of ± dx.
In order to obtain a narrower major lobe in the directional diagram of the offset antenna, antennae are manufactured which do not have an even surface (Fig.4). These antennae also have a plane of symmetry y = f, 2a and t can be measured in this plane. The interval 2b can be measured in a plane which runs vertically to the plane y = diameter and which contains the points (x1, z1) and (x2, z2). To put it another way, for any even section selected through the surface of a rotation paraboloid, the points (x1, z1) and (x2, z2) can be obtained, which make it possible to measure the lengths 2a, 2b and t. All the parameters can indeed be measured on a punched-out offset antenna.
There remains only the problem of the correct classfication of points (x1, z1) and (x2, z2), which are in the plane of symmetry. In theory the classification is clear, but in practice there are always problems, so appropriate manufacturers' markings would be of assistance. The point (x1, z1) lies at a position on the edge where the curvature of the section in the plane y = f is greater than the curvature at point (x2, z2). In many cases, only after precise antenna measurements can it be determined that the two points have been transposed.
Fig.5 shows some examples for offset antennae. Here a focal length of 35 mm. is selected, and then some calculations are carried out. The relevant parameters and results are shown in table form. If we use the BASIC program, we must initially increase the intervals after entering the standard parameters. The standard accuracy has been retained, N has been defined as N = 2, and finally N = 3 has been selected, which led to a solution. In the second case, it was not necessary to alter the standard parameters. In the third case, in which the section ran through the impermissible area x1 = f, the intervals had to be increased again. So G = 0.00001 was selected and x1 calculated. The area around x1 = f can be avoided if the input parameter is altered "infinitesimally". In practice, this case presents no difficulties, and so no special researches or calculations were needed. In the fourth case, a higher accuracy was selected for x1, from x = 0.1 mm. to x = 0.01 mm.. If we lay down that 2a = 2b, we are pre-setting the values of a symmetrical parabolic antenna, which is shown in Fig.5.
In accordance with the principles set out above, here are some explicit examples of the application of the program:
1. Establishing focal point: a. For correct placing of radiator; b. Determining phase centre of radiator used
2. Modification or copying of given parabolic antennae.
regards from OZ bassett
Do as Basset said adjust your lnb by rotating it slowly and watch the signal quality. Rotate it until you get the best quality on the weaker signals then carefully tighten it up .
Also check to see no spiders or anything else is blocking the lnb's throat.
Then sit back and enjoy your sat tv.
Thanks for the information. I was searching over the internet to find the focal point for offset dishes and now
" 李俊明 Born To Help People "
DM 500s , Pacific 3600 CI , Humax F2 Finder , Angel Box , My Dream Machine , Tatasky , KAON , Topfield 3030 , Yuri YR1Dap , Dynasat 7100 , F1 , Plus and II , Metabox II , 10 , Viva Vs 9000 , SkyBox II , X-Sat 430 , 420 , Bolt N2 , NewB , New Shine Ns 3000 , Victory V 889 , F1 Newshine , New Star , Innovia 3088 CA , Atom 7000 , PBI , Prosat , Dstv 3Q76 , GA 88a , Tatasky , Big Tv , Airtel .
I'm not attacking anyone, I simply stating facts, and lets face it, you have writern 4000 + posts and said absolutely nothing or substance or value.
You did post a thing about J-tagging which you stole and copied word for word, from someone on another forum, and did not have the good manners to credit them
But having said that, what you have once again done is pollute a perfectly good thread with off-topic rubbish, to enticed a reaction from me. Your a bloody disgrace
regards from OZ bassett
Really your question has aready been answered, in this thread. Like all things if you have the right gear, your half way there, But unless your using a large dish be it Prime Focus or Off-set, with the correct LNB
set-up, your going to have problems. Unless your directly below th satellite , with such a strong signal, that anything with work.
If you could supply details of your current set-up [dish size, etc]
and the satellite and transponder, your trying to access, then we might be able to advise accordingly
regards from OZ bassett
Dear Nasir, I too faced this problem since last month where some TPs were giving me low and sometimes NO Signal.. i was using 17K lnbf.
but then one day i put 15K lnb and checked it, and to my surprise i am getting quite a good signal on the Peace tv, ARY, Hum tv, Dawn, and other TPs which you are getting low signal.
so just try to get 15K LNB and put it , no need to changed or adjust your dish or scalar ring now.. ok just try with 15K first.. i am confident you will succeed.
now i am getting more than 60% signal for Peace tv tp 3784 H 3251, whereas before i used to get only 30% or even less .
You cannot teach a man anything; you can only help him find it within himself.
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