Combiner

[magno22]

Dears,
I need to combine UMTS900Mhz and GSM900Mhz. Please suggest me combiner which is very low loss.

[Optimustron]

All combiners are basically the same, the only real loss is the division of power, if you have two outputs you'll have 3 dB minus almost at each output, If you do the math then when you add the values at the two outputs you'll have almost the power at the input, the real loss is the insertion loss that is basically low, however there are two kind of combiners, resistive and hybrid, the first ones have resistors, then compared to the second ones they are lossy because the second type of combiners use transformers that have less loss.

By the way you need to compare the insertion loss of two products and you can get this way the product with less loss, but I recommend you that look for LOW PIM combiners because if not you'll have problems with intermodulation and I suppose that you will need loads you will need to look for LOW PIM too, I recommend you PIM LOW as -165 dBc if possible, however for UMTS with -130 dBc is good.

I hope this can help you, best regards,

[magno22]

What is best solution of GUrefarming on rural area? Currently GSM base stations already installed.

[Optimustron]

We did that work in all our country, we made a spectrum cleareance in order to leave it for UMTS, by the way is better to have UMTS at lower band not upper in order to reduce some problems, specially with armonics.

We didn't use combiners, we put another sets of antennas because this way is less complicated and you can isolate one cause of IMD/PIM because is hard to have a clean installation if your FIELD SERVICE team is not very well trained and commited to have a good network, that depends on the way they are measured in terms of job, because they can have metrics that only take in consideration if a particular site is up and running and doesn't care about the proper installation and good quality.

The most simple are the installations the better to isolate problems and failures, one system can be up an running and the other is down, then you don't lose coverage.

Another thing to consider is how old are the antennas, jumpers and feeders of GSM then is better to beging with a fresh and clean installation for UMTS. You need to consider your antenna settings too for the old system because almost sure you will need to put another settings for UMTS, specially because you surely will need to reduce coverage for UMTS in order to have good quality.

I hope this can help you, best regards,

[Optimustron]

Hi Friends, this is only an update about of accepted PIM values, this is a criterion from ANRITSU, they said that in order to see if you have a good RF environment you need look at this values if you use a PIM TESTER with two carriers with 20 watts/43 dBm, you can do the maths is the difference between dBc and dBm:

• Examples of PIM Measurement Values

Very Good: < -150 dBc / -107 dBm
Good: -140 dBc / -97 dBm
Poor: -130 dBc / -87 dBm
Abysmal: > -113 dBc / -70 dBm
Best regards,

[nron3]

hi optimustron,
may you please explain more about pim test.
my team have done it before but i do not understand...
many thank.

[absoares]

It would work better if you consider logical share instead of a combiner. If you are working with E******* you can used the MSMM - Multi Standard Mixed Mode to combine the GSM900 with the UMTS900