 This topic has 28 replies, 1 voice, and was last updated 12 years, 3 months ago by tilter.

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MohitGuest
Hi All…
One of my friend has recently gone through an interview…and the interviewer asked him two questions…
1) wat is the formula for calulating/ deciding electrical tilt for a site.
2) how many TCH are required during a Confrence call..
Pls do reply if somebody have any idea regarding these above question…
Regards..
Mohit..pixGuest1> geometrical calcula : depending on height of antenna, expected cell range and vertical aperture of the antenna, one can compute the required tilt in order to locate the upper “3dB” point onto the cell range.
f(H, CR and VHPBW) –> tilt
the formula uses “tan” function… i let you find it by yourself 🙂2> only one TCH per user.
MohitGuestThanks Pix…
But can u explain this formula a little more…i mean with an example…
Regards..
MohitpixGuestMohit,
i hope you didn’t kill yourself trying to find the formula, huh.
cell range = Height BTS / (tangent(tilt – VHPBW/2))
example : height = 30m
VHPBW = 8 degrees
tilt = 6 degrees–> cell range = 30/tan(radians(6 – 8/2)) = 859 meters.
MohitGuestMany Many thanks Pix…
🙂MKTGuestPix..
How will you find the 3 dB point from BTS?
Does the formula takes into account the BTS Tx Pwr Max?
Regards
MKT
pixGuestthe 3dB upper point is taken into account in the formula (–> VHPBW/2)
the BTS power does not matter in this formula. What matters is how far you want to locate your “3dB upper point” (=cell range). The BTS power will then give you the “intensity” of the coverage within this cell range.
regards
pixMKTGuestPix
what is VHPBW?
Regards
pixGuestvertical half power beam width… it is the vertical “aperture” of the antenna. You can see it on the antenna specifications. Usually around 8 degrees.
Nitin TomarGuestWhat is the significant of Vertical beamwidth in coverage???
PixGuestNitin, isn’t it explained just one post below ?
baigGuestIs the tilt in the formula got from sum of electrical and mechanical tilt or its just the electrical tilt? how does mechanical tilt affect the formula
PixGuestIn the formula, you should use the sum of electrical tilt + mechanical tilt.
AhsanGuestI really acknowledge ur effort regarding helping other optimizers and learners..
Well it means that we have to take effective tilts into account.
Also i wanted to know the individual effect of mechanical and electrical tilt.
Well as i have experienced.. mechanical tilts adds backlobes.. question is Y.?
PixGuestHello,
Mechanical tilt : increase downtilt in front, but since you’re tilting the whole antenna, you see that the backlobe will get uptilted, yes? ,
Electrical tilt: all directions around the antenna are tilted down, like when you’re closing an umbrella : all sides are getting down at the same time.

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