Repeater Measurements Question

[hooby]

Hi guys!
I have a question about measuring RF parameters of repeater system. I have to measure Andrew repeater model MR 303/403 (dual band). RF parameters which i have to measure are DL Rx Power (dBm), DL Tx Power (dBm), UL Rx Power (dBm), UL Tx Power (dBm), DL Gain (dB), UL Gain (dB). Can someone explain what exactly means everyone of the parameters, because I get different answers from everyone i ask. Can you tell me if there are any formulas from which you can calculate some of the parameters, based on measured other parameters. If you have any documents about these type of measurements can you please share. Thanks in advance!

[indoor]

Hello Hooby,

I will have a look to see what documents I have that may explain this better for you.

A quick explanation is that these measurements all relate to what the repeater is seeing.
So Downlink RX power is how much signal strength the repeater sees from the Donor BTS. The Downlink TX power is then at what level the repeater sends this signal out to the mobiles. The Downlink gain is just the difference between these two and is essentially by how much the repeater turns the volume up on the signal it is receiving. The Uplink versions are the same but in the direction from the mobile to the BTS.

Also powers are measured in dBm and gain is measured in dB.

Hope this helps.

[wolverine]

Shouldn't the gain be measured in dB?

I guess the gain is given by the manufacturer. The Rx values will depend on the radio conditions. The Tx values will be the Rx values plus the gain.

I am not an expert though..

[indoor]

The gain is usually set depending on what signal is received in the downlink and then by how much the signal can be turned up based on the power rating of the repeater. Bit like a hifi system turn the volume up too high and the signal distorts. Another factor is the isolation between the donor antenna and the delivery antennas. Again like a hifi system if you're singing karaoke and you stand in front of the speakers with the microphone you get a feed back loop and that high pitched squealing. Gain needs to be 10-15dB below the isolation, but some of the Andrew repeaters have a feedback cancellation system so the gain can be higher than this limit. Uplink gain is usually set a few dB below the downlink so as not to add too much noise to the donor BTS.

[indoor]

This document whilst old covers most of the ideas for setting up a repeater.

[hooby]

thanks a lot for this useful info! :)

[indoor]

I also came across this antenna isolation calculator. This is only calculated and can't be relied upon in most cases as there may be additional losses due to walls or less loss due to reflections. However if you are looking at something like a rural pole mount repeater it will give you a good idea if your plans are workable or not.

[harrypotter]

NIce post... thank you so much

[ner0]

nice!!!!!! i just want to download the file...
How do I get to be a member user?

[xpdxtd]

Antenna isolation is measured by transmitting a "clean" frequency in the distributed indoor antenna system (DAS) and receving this frequency at the feeder connected to the donor antenna. The difference between transmit and received signal is the isolation level in dB and determines the maximum amount of gain allowed with the formula: Max_gain=Isolation-15 (dB).

[hamody2005]

nice discussion thanksssssssssssssssssss

[Fado]

nice!!!!!! i just want to download the file...
How do I get to be a member user? hi,you should post more comments or share some documents so pple will give you a thumb up which will increase your reputation..i just gave you one..will appreciate if you do the same :)