RX Gain (UHD vs libusrp2)

GNU Radio
1

Hi all,
I’m in the process to migrate our software currently using the old
libusrp2 to use the UHD.
My daughter board of reference is the WBX.
With the libusrp2 the gain range was [0, 31.5] while with UHD is [0,
38].
I have noticed that now with UHD is possible to set (apart the overall
gain chain) the gain for the following elements:

WBX-PGA0 with a range [0.0, 31.5]
ADC-digital with a range [0.0, 6.0]
ADC-digital-fine with a range [0.0, 0.5]

this means that using the libusrp2 those two ADC gains were set to 6.0
and 0.5 giving then the user the ability
to change only the WBX-PGA0?

Even setting ADC-digital = 6.0, ADC-digital-fine = 0.5 and setting the
WBX-PGA0 to same value used with libusrp2
the result is not the same as in I’m losing something like 20 dB.
Is this expected ?

Regards
Gaetano M.

–

2

Even setting ADC-digital = 6.0, ADC-digital-fine = 0.5 and setting the
WBX-PGA0 to same value used with libusrp2
the result is not the same as in I’m losing something like 20 dB.
Is this expected ?

Missing 20dB sounds like maybe you have the other antenna port
selected. Have you tried swapping antenna ports or using a call to
set_rx_antenna() to explicitly select your antenna port?

Jason

3

On Mon, Mar 28, 2011 at 2:02 PM, Jason A. [email protected] wrote:

Even setting ADC-digital = 6.0, ADC-digital-fine = 0.5 and setting the
WBX-PGA0 to same value used with libusrp2
the result is not the same as in I’m losing something like 20 dB.
Is this expected ?

Missing 20dB sounds like maybe you have the other antenna port
selected. Have you tried swapping antenna ports or using a call to
set_rx_antenna() to explicitly select your antenna port?

You were right, indeed without the set_rx_antenna the selected antenna
was RX2 while I have connected the TX/RX, using the set_rx_antenna to
TX/RX I’m getting now the expected powers.

If I have to use the device as receive only do you suggest to use the
RX2
connection ?

Regards
Gaetano mendola

–

4

On 28/03/2011 10:02 AM, Jason A. wrote:

Even setting ADC-digital = 6.0, ADC-digital-fine = 0.5 and setting the
WBX-PGA0 to same value used with libusrp2
the result is not the same as in I’m losing something like 20 dB.
Is this expected ?
Missing 20dB sounds like maybe you have the other antenna port
selected. Have you tried swapping antenna ports or using a call to
set_rx_antenna() to explicitly select your antenna port?

Jason
Also, the USRP2 has no VGA in front of the ADC – the only gain control
you have is the WBX itself, which is a total range of 31.5dB, AFAIR.