- This topic has 58 replies, 1 voice, and was last updated 17 years, 5 months ago by
.
-
Posts
-
good luck !
Hi,
I want to install two BTSs at one site. One BTS is an 900MZH and the other is 1800MHZ. I don’t have dual band antennas so I have to install for every BTS 3 sectored antennas, to cover the 360 degree. So how do I have to place the antennas? Is this true that it is better to place the 900MHZ antenna on the top, and the 1800mhz antenna 1.5m lower than the 900mhz. is there any a recommended distance between two the three sectored antennas within one BTS? I have a single thin pole but is is very strong, connecting all the tree antennas of a single bts will bring each antennas 5 cm close to one another? Can this create a problem
Any ideas pleaseHi Abdel,
I think there is no need to place the antenna under the 900 MHz antenna, because these are 2 different bands and hence there is not any impact on the performance of the entire system due to any of them unless you have civil constraits to put them all together.
Cheers !
Abdel,
it is true a separation between the antennas of the two different bands (900 and 1800) is needed. It is about 1.5m for a ‘vertical’ separation as far as i remember.
You’d rather put the 900 antennas on top, because they’re meant for coverage. Therefore putting them on top give them even more coverage.
And finally, you can locate antennas from the same band just few centimeters apart. It is OK. If you have a single pole, you can place your three 900MHz antennas at the same level, each of them facing a different direction (0/120/240). And put the three 1800MHz antenna 1.5m lower (bottom/top separation) with the same configuration.
You will also need antenna supports (clamps and stuff) to perform this operation. Check which one will let you do such a mounting.
Don’t do such things. Are you sure you need different azimuts for the different bands. Instead use Dualband antennas.
yeah… dual band x-polar antennas are the way to go 🙂
I am working on a cdma450 system with X pol, 65 deg. antennas, 43dBm max tx power, in a rural area with very low subscibers.
I want to know the effect I ll get if I point 2 of the 3 sectors 70 degrees apart. I need to do this to get small clusters of subscribers in each of the two sector directions at more than 50 km from the bts.
1. the overlap area will not have alot of users – it is mostly unoccupied bush
2. will only use FWTs on the system and not mobiles, as a wireless local loop system.
Does anyone have any similar experience on a cdma system? worried bout pilote polution and Eo/Io.
Bauer,
At 70°, the antenna beam has an attenuation of about 13dB. So without taking into account the multipath reflections, the “best” signal strength difference between both sectors is 13dB.
It might be less.
Example : clutter 1 at azimuth 0°, and clutter 2 at azimuth 70°.
Why not try the following:
sector 1 is facing clutter 1 – 20° (340°)
sector 2 is facing clutter 2 + 20° (90°)Hence, you’ll have 110° separation = signal strentgh difference of 24dB. Sounds better 🙂 Your antennas will still provide a good coverage, because you’re in the 65° hbpw primary lobe.
Last solution, use only one sector to shoot right in the middle of the two clutters (azimuth 35°). And you’ll have about 4 dB loss at the clutters (you’re slightly out of the main lobe)… maybe less if you have some reflections… and if you use 2 rx div, 4 rx div, TMA ? you’ll get those 4dB back.
Hi pix,
Here customer using a XHAT-90 deg.,43dbm antena on gsm900.is thre any cov.effect in overlap zone, if antennas r installed at 75 deg apart?cn i gt relation o/p power vs distance for that antenna smwhre.
BR//
yogesh_rfyogesh,
in gsm900 there will not be any problem. Just a higher amount of pbgt handovers in the overlap zone, but nothing dramatic.
you can find your antenna patterns on the antenna vendor website, or on the vendor catalogue (www.kathrein.com , RFS , alan dick ,…)
and the antenna gain is measured in dBi, and range usually from 5dBi to 22dBi. When you’re talking about 43dBm, I guess it is the output power from the BTS.
Hi all,
my opinion, if there is space on the tower, better put antenna GSM1800 on the top, higher than antenna GSM 900 (if there is space for antenna GSM1800). ==> because of propagation
If there is no space, better swap it to dualband antennas.
For 2G system to 3G system the separation is 0.5m (edge to edge) for vertical and 1 meter separation when installed horizontal separation.
thanks
Hi Pak Willi,
How are you BOZZ ?? Are you remember me 9 ( each one team working for you in project NPI Jakarta), i have one question. Why antenna of 1800 better put on the top higher than antenna 900 ??
Caused all of site each one of provider on sumatra antenna 900 placed higher than antenna 1800.dear herebowo
can you please give me the formulae for the result that you reach or it result from field experience
thankshi all friends
i ask which is the distance between antennas in GSM9000 and GSM1800,Why?
Best regardhi tahseen,
why what ?
the minimum distance between antennas is dependent on the BTS hardware itself (especially the duplexer). Your vendor should be able to tell you.
For Alcatel, the minimum distance is about 30 cm, vertically, to ensure enough decoupling.
- The forum ‘Telecom Design’ is closed to new topics and replies.
