- This topic has 28 replies, 1 voice, and was last updated 12 years, 1 month ago by tilter.
24th July 2008 at 14:12 #53193MohitGuest
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…
Mohit..24th July 2008 at 17:27 #53194pixGuest
1> 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.25th July 2008 at 11:02 #53195MohitGuest
But can u explain this formula a little more…i mean with an example…
Mohit25th July 2008 at 12:02 #53196pixGuest
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.25th July 2008 at 14:28 #53197MohitGuest
Many Many thanks Pix…
🙂28th July 2008 at 08:49 #53198MKTGuest
How will you find the 3 dB point from BTS?
Does the formula takes into account the BTS Tx Pwr Max?
MKT28th July 2008 at 14:48 #53199pixGuest
the 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.
pix29th July 2008 at 08:17 #53200MKTGuest
what is VHPBW?
Regards29th July 2008 at 17:34 #53201pixGuest
vertical half power beam width… it is the vertical “aperture” of the antenna. You can see it on the antenna specifications. Usually around 8 degrees.25th February 2009 at 06:16 #53202Nitin TomarGuest
What is the significant of Vertical beamwidth in coverage???25th February 2009 at 07:26 #53203PixGuest
Nitin, isn’t it explained just one post below ?26th February 2009 at 08:15 #53204baigGuest
Is 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 formula26th February 2009 at 11:10 #53205PixGuest
In the formula, you should use the sum of electrical tilt + mechanical tilt.25th March 2009 at 06:30 #53206AhsanGuest
I 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.?25th March 2009 at 12:04 #53207PixGuest
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.