Trouble Shooting Guide

Axxcelera Broadband
Troubleshooting-Installing an RF link - 30 - Issue: 5.3.x
Rev 2
10 Modem txpower
The “hmm modem txpower” command is available on both APs and SUs.
AP Modem Txpower
192.168.100.200 hmm> modem txpower
corrected FCC backoff tx attenuation +17.466 dB
nominal TX chain attenuation 16 dB
actual TX chain attenuation +16.937 dB
digital baseband attenuation +0.638 dB
nominal TX power +1.000 dBm
actual TX power +0.891 dBm
Of the six numbers reported by “hmm modem txpower” on an AP, only three are of any real value for
debugging RF problems : “actual TX chain attenuation”, “nominal TX power” and “actual TX power”.
10.1.1 corrected FCC backoff tx attenuation
Corrected FCC backoff tx attenuation is the amount of attenuation required in the transmit path to keep the
transmit power at or below the FCC limit for that channel/polarization.
10.1.2 nominal TX chain attenuation
Nominal TX chain attenuation is the amount of attenuation (in terms of 2dB attenuator pads in the radio)
that should be placed in the transmit path to achieve the nominal TX power.
10.1.3 actual TX chain attenuation
Actual TX chain attenuation is the amount of attenuation that is actually placed in the transmit path if the
nominal TX chain attenuation is switched in. This uses unique calibration information to calculate the
actual attenuation of each 2dB attenuator pad in the radio. If this number is zero, or very close to it, then
the unit may not be able to transmit at the requested nominal TX power level. This may cause intermittent
downstream or upstream RF problems.
10.1.4 digital baseband attenuation
The digital baseband attenuation is the amount of attenuation that is placed in the transmit path by the radio
processor. It is used to set the radio attenuation very close to, but slightly below, the desired nominal TX
power level.
10.1.5 nominal TX power
Nominal TX power is the maximum amount of power (dBm) that should be transmitted from the AP radio,
based on FCC regulations, i.e;