- This topic has 58 replies, 1 voice, and was last updated 13 years, 8 months ago by Da Architect.
17th September 2005 at 13:58 #42202antennaGuest
Does anybody know if there will be a problem if you place two antennas in the same direction side by side. What is the minimum distance so that the antenna pattern is not much influenced. I am not talking about the antenna isolation but for the phisical influence of the neigbour antenna as obstacle. The Antenna is GSM 900 65deg H-Plane.18th September 2005 at 05:46 #42203monemGuest
th max distance between two antenna in same cell is 16macrosecond(4.5 km)=(GSM equalization window).
but bacing antennas side by side will cause strng intermodulation which cause high interference(same frequ for two). but if you use diff freq with high duplex distance it will be (no problem).19th September 2005 at 14:12 #42204AntennaGuest
I am talking for example for two antennas one is GSM900 and the other GSM1800. If they are pointing in the same direction. For example imagine that they are mounted on two side extensions of a pole. What is the minimum distance in that case.
thank you in advance19th September 2005 at 14:42 #42205PatrickGuest
We are doing that here.
30 cm (centimeter) it is a good distance and there isn’t problem.19th September 2005 at 15:15 #42206AntennaGuest
do you mean that the antenna pattern is not changed much when you have an obstacle (in our case antenna) around 30 cm at 90 degree from the direction of our antenna.
Boicho19th September 2005 at 16:25 #42207monemGuest
we dont assume any distance between them , we do it for 900, 1800, UMTS in the same sector without any distance ( just distance for maintenance and mounting) because there is no intermodulation & no interference …so no effect on C/I20th September 2005 at 05:35 #42208antennaGuest
Do you know where I can find some recomendations about this, even a picture with kathrein engineers mounting the antenna this way will be enough.20th September 2005 at 14:49 #42209PatrickGuest
The most important think is coplaner: vertical or horizontal
the magnetic fields is in front of the antenna.21st September 2005 at 08:46 #42210antennaGuest
I find it hardly to explain this to a colegue of mine without something on paper. I will be very grateful if you share more info.13th December 2005 at 20:08 #42211MihaiZGuest
I think the most important thing is to take into account the border between the Near-Field vs. the Far-Field of the antenna. The formula is:
where D is the largest dimension of the antenna and Lambda is the wave length.
So, for panel antenna, 2m long and working in 900MHz band, Rff=24m!!!15th December 2005 at 08:25 #42212AntennaGuest
Do you mean obstackes in near area? Because I am talking for three antennas side by side – one is GSM900, second is DCS1800, and the third is UMTS. They have the same azimuths. For example imagine that they are mounted on two side extensions of a pole and on the pole. What is the minimum distance in that case?20th December 2005 at 10:28 #42213BobooGuest
if the antenna have the same azimut and the are set in the same row, the minimun distance is about 1,50 meters. one antenna is a bit in front of the second, they should not have the same azimut. for example, if both have 0° for azimut. you had to change the azimut for the behind one if this antenna is at the right side of the second one. Then the azimut will be 20° for example.
I hope it was helpful for you
Boboo6th June 2006 at 10:45 #42214dscGuest
I think i have been puttin this question in the wrong place! I hope i ll get help from here.
I have to install cdma450 antenna on a tower that has gsm900 antennae already on it. Question is , is there any vertical isolation rules i need to observe for this situation?7th June 2006 at 19:08 #42215pixGuest
you need about 30dB decoupling between the two systems (GSM900 and UMTS). As far as I know, you can place both antenna systems right next to each other, and the decoupling will still be higher than 30dB.
Out of safety, I’d keep a distance between the bottom of higher antenna and the top of lower antenna of :
Dv > 50cm
(50cm provide a decoupling of about 50dB)8th June 2006 at 17:42 #42216dscGuest
Thank you PIX,
We have installed the antennae with somethin like Dv= 60cm. We will commissioned the site for cdma450 tomorrow! I ll keep you posted on the actual field results.