Receiver gain issues with USRP2 and XCVR2450

Hello Everyone,

My questions are related to the Gain (set by ‘set_gain()’ method) set in
receive chain particularly in ‘digital’ folder in gnuradio-3.2. I am
USRP2 with XCVR2450.

The receiver gain is set to default (46 dB) in most of the scripts
ofdm, usrp_fft etc.). My guess is that high gain is perhaps pushing the
input signal out of the dynamic range of ADC and therefore saturating
ADC output. The SNR (as seen in is low (20-25 dB) in this
Lowering the gain (< 30) solves the problem (SNR 60-70 dB) and packets
successfully received in This problem was never found
USRP1. What is the cause of this problem to occur only in USRP2 ?

  1. Does set_gain() set the analog gain ? (i.e. gain of a programmable
    amplifier before the ADC or on the daughterboard) or is it digital
    of digitized samples) ?

  2. Shouldn’t we have an AGC in all the ‘’ where gain is
    calculated as the mid-point of the gain range ?

I went through the previous posts on AGCs. They discuss the AGC settings
general which I understand, but my issue seems to be specific to USRP2’s

Any help in this regard would be greatly appreciated.