Operating in low modulation


we have deployed PMP450i and once the SM integrated into the AP with a 2km link distance, it looks to operate in low modulation,
RSL -49.5 dBm (-52.0 dBm V/ -53.0 dBm H)
Registered 8X/2X MIMO-A.
Expected to operate in 8X/6X MIMO-B.
Does anybody have an idea this behavior is normal or due to any complication in the unit or configuration?

Also, have details of the threshold for each modulation level in PMP450i (16.2.3)?


If your screen cap is correct your uplink power level is -97 which would explain your low modulation level and I’m surprised you can maintain a stable link at all. Check your power and antenna gain setting on the SM.under configuration - radio. Is this an integrated radio? If its connectorized you could have a bad antenna/cables.

Hi Riverrat,

Thanks for the response, here we are using the integrated radios. also, we configured 23dBm as TX power in the Radio parameters of the SM,

Can it be due to physical equipment failure,

in the attached figure,
Transmit Power: 20dBm
Max Transmit power: 23dBm
Power Level: -97.0.

So you are concerning about Power Level, so I have question why this power level is going down even the TX power configured to 23dBm.


On the AP, disable “Adjacent Channel Support”, and set the “SM Receive target level” to -60dBm.

ALSO, if you’re using 450i you should upgrade your firmware to release 20. A major notable benefit to this is intermediate modulation modes or “IMM”… which adds 3/5/7 modulation steps.

Hi Eric,

I have disabled the Adjacent Channel Support and Set the target power level to -60, and the situation is worst now,
Snap from AP

Snap from SM

Yikes! The SnR seems to indicate that you have a noise floor in the -70’s… that is not good.

You might want to increase your AP transmit power to 25dBm, and increase SM Receive Target Level to -55dBm.

Can you please show us an spectrum analysis scan on both the AP and SM?

Have you tried finding a cleaner channel to run on?

What channel width are you using?

Configured here 20MHz, and assigned the approved channel received from the authority.
Configured freq in SP : 3650 MHz

Configured the TX and SM RX target levels:

snap from SM:

Spectrum from AP:

Spectrum from SM:

It looks as though someone is running a 20MHz channel centered on 3650 very close or on the same tower as you.

If you’re running back to back frequency reuse and this noise is being created by you, then you will need to make sure that all relevant settings are matched and/or you’re using Cambium’s sync calculator to make sure that your sync settings are correct. You will need to follow Cambium’s recommendation on antenna specifications and placement in order for back to back reuse to work optimally.

If you are not the one creating this noise, then the energy levels are too high and you will need to find a different channel. Unfortunately, ATM, SAS’s aren’t aware of other operators operating on assigned frequencies, so you will still need to do some work to find a clean channel and/or coordinate with your competitor. Worse case scenario is someone operating pirate-style and not using a SAS.

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