RTWP unbalanced

**mirc84** · 2010-06-11, 06:30 AM

Hi,

I have the following issue. I'm working on a Huawei BTS and in RTWP monitoring the RTWP values of one sector of main and diversity branch differ by 10 dB. main branch has -89 while diversity branch RTWP is at -105 dB.
I'm using a 12dB gain TMA and the RXATTEN is set to 10dB.

My question is why is this big difference of RTWP? Is it just a passive intermodulation or could be also some kind of external polarized interference?

Thank you!

**Finetopix** · 2010-06-11 06:30 AM

**danikd** · 2010-06-11, 03:26 PM

Originally Posted by mirc84

Hi,

I have the following issue. I'm working on a Huawei BTS and in RTWP monitoring the RTWP values of one sector of main and diversity branch differ by 10 dB. main branch has -89 while diversity branch RTWP is at -105 dB.
I'm using a 12dB gain TMA and the RXATTEN is set to 10dB.

My question is why is this big difference of RTWP? Is it just a passive intermodulation or could be also some kind of external polarized interference?

Thank you!

It seems that you have a cross-connect!!!! Each sector has 2 RF cables (diversity A and B) and for some reason during installation one cable was connected to the wrong antenna!!!!

It is a typical situation when you have not a full sector cross-connect, but only single cable cross-connect.

Check other colocated sectors for similar problem, then try to identify which cable has been cross-connected.

**Cheuv** · 2010-06-11, 05:29 PM

Dear Friend,

I use to work RTWP getting help from below document.

http://www.4shared.com/file/vAcQtyqa...sing_Guid.html

Hope yuo will find it as useful as I think it is.

Enjoy, also Thx and rep will be welcome

Have nice day and enjoy external interferences

**mirc84** · 2010-06-11, 05:47 PM

Originally Posted by danikd

It seems that you have a cross-connect!!!! Each sector has 2 RF cables (diversity A and B) and for some reason during installation one cable was connected to the wrong antenna!!!!

It is a typical situation when you have not a full sector cross-connect, but only single cable cross-connect.

Check other colocated sectors for similar problem, then try to identify which cable has been cross-connected.

Thanks for the answer!
Based on your supposition I should also see another sector with -105 on main and -89 on diversity, right?
Unfortunately i did not see this situation.

I hope I'll have some ideas after I read Cheuv's document. anyway I'm still open to oppinions.

**dremka** · 2010-06-20, 10:07 PM

Hi.

I've got a lot of RTWP unbalanced problems in my network. Most of them are caused by passive intermodulation. It's charcteristic - the problem is visible only at tx (main) branches and dissapears as you block the transmitter. In case of external interference two branchces should indicate similar (+/- 3 dB) signal level (if they're identical!). The problem in my network is worsen by the dual band antenna - this is the intermodulation between systems, an IMD3 product unfortunately falls directly into rx band of the affected system... There are also several cases of intermodulatiuon caused in single antenna by an "own" transmitter only.
The problem is a result of improper installation regime - not properly sealed connectors corrode and make nonlinear connections. It's usually not visible in vswr test nor even in DTF analysis.
So, switch off transmitters and see what will happen...