Problems inherent to bringing 4C (4th Carrier) up?

[MountainLion]

Anyone find a connection to internal RSSI issues in 2C when 4C is introduced?

[Anritsu]

An internal RSSI alarm usually indicates an Rx noise floor imbalance.

In my experience this is passive intermodulation, and is quite common when the 3rd and 4th transmitters are added and should be present on the line that the Tx's use.

If the noise is present on both lines, it is likely external interference but try wilting a couple of Tx's to see if the problem stays or goes.

best regards,

Nick

[MountainLion]

An intermod caused by what element of the system? The problems I'm seeing appear to be internal on both 2C and 4C, or 1C and 3C, but only show themselves when the 3C or 4C are introduced. The RSSI issues appears on both sides respectively: When 4C is introduced, 2C and 4C have elevated RSSI's, introduce 3C and 1C +3C will too, under these circumstances.

The configuration that's most common for 2C/4C: no changes to antennas or their feedlines, but an lengthened bulkhead jumper to reach to the 4C cab. Port B of 2C's FU is redirected to Port A of 4C's FU. So the dedicated RX for 2C, is now a TX/RX for 4C.

So, what do you think?

Also, do you know of any issues caused by the FU and/or the RU Port B being unused, while cross connecting (co-locating) RX cables to 2C and 4C?

Thanks Nick.

PS: No outside sources detected in this scenario.

[rudypoot]

Could the introduction of additional jumpers, splitters and couplers cause this issue?

[MountainLion]

Could the introduction of additional jumpers, splitters and couplers cause this issue?

In the "typical" set up, there are no additional jumpers, splitter, or couplers... Branch B of 2C is simply converted to Branch A of the 4C (They may change out the bulkhead jumper to reach the Radios), and share an auxiliary RX Radio, and Filter Unit port as not to lose the RX performance of each cabinet by not utilizing the Branch B Antenna Ports of the FUs.

My hunch is: its in the configuration of cross connecting the RX RU and FU leads. Its a fairly new configuration, and nobodies talking about the potential of interference in using an "unorthodox" method of sharing antennas by doubling up on TX on both antenna ports, and splitting off the RX from each port at the equipment. Follow?

[rudypoot]

I do follow and I agree with your thoughts, Splitting always comes with some type of loss.