 # Values of gain differ with Python and C++

Hello,

I have seen in the file usrp_basic.h that the minimum value of the gain
is -20 and the maximum is 0. And in the user guide of the USRP, it is
written that the PGA has a maximum gain of 20 dB.

But with Python when you call subdev.gain_range(), the minimum value is
0 and the maximum value is 90. Is it the same? With Python it is just a
different representation?

Thanks

Julian

On Sun, Nov 05, 2006 at 01:42:30AM +0100, De Lima Julian wrote:

Hello,

I have seen in the file usrp_basic.h that the minimum value of the gain
is -20 and the maximum is 0. And in the user guide of the USRP, it is
written that the PGA has a maximum gain of 20 dB.

Yes, this is true, for the PGA in the AD9862.

But with Python when you call subdev.gain_range(), the minimum value is
0 and the maximum value is 90. Is it the same? With Python it is just a
different representation?

There’s additional gain available on the daughterboard. We give you a
single knob that adjusts both values.

Eric

Hello,

I have seen in the file usrp_basic.h that the minimum value of the
gain
is -20 and the maximum is 0. And in the user guide of the USRP, it is
written that the PGA has a maximum gain of 20 dB.

Yes, this is true, for the PGA in the AD9862.

But the AD9862 is only used for the transmit path. For the receive path
is the PGA implemented with the FPGA?

Why on the usrp_basic.h there are 2 functions for set_pga(), pga_min(),
pga_max()? The maximum gain for 1 is 0dB and for the other it is 20dB
and the minimum gain is -20db and 0db?

But with Python when you call subdev.gain_range(), the minimum value
is
0 and the maximum value is 90. Is it the same? With Python it is just
a
different representation?

There’s additional gain available on the daughterboard. We give you a
single knob that adjusts both values.

What is the unit?

Thank you

On Mon, Nov 06, 2006 at 04:53:09AM +0100, De Lima Julian wrote:

Hello,

I have seen in the file usrp_basic.h that the minimum value of the
gain
is -20 and the maximum is 0. And in the user guide of the USRP, it is
written that the PGA has a maximum gain of 20 dB.

Yes, this is true, for the PGA in the AD9862.

But the AD9862 is only used for the transmit path.

An assertion like that tells me that you haven’t read the AD9862
datasheet, usrp_basic.h, usrp_standard.h or looked at the schematics.

Eric

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