[Discuss-gnuradio] Gain distribution with Flex 400

[Sivan Toledo]

How is gain distributed when the UHD USRP block is told to set the total gain to a particular value?

I am using GRC with UHD controlling a USRP with a Flex400 daughter board. I set the gain in the GRC block to 20dB, which results in the line "self.uhd_usrp_source_0.set_gain(20, 0)" in the Python output file.

My understanding is that the codec on the USRP has an internal PGA whose gain can be set between 0 and 20dB and that the Flex400's mixer also has a PGA whose gain can be set between 0 and 45dB.

Does this mean that I can set the gain in the USRP source block to anywhere between 0 and 65dB (with the driver deciding how to distribute the gain between the two PGAs), or is there a way to control separately the two PGAs?

Thanks, Sivan Toledo